Patent Publication Number: US-2007109137-A1

Title: System and method for reporting information indicative of the sealing characteristics of a sealed compartment

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
      This application claims priority to U.S. Provisional Application No. 60/729,901, entitled “Leak Detection System and Method,” and filed on Oct. 25, 2005, which is incorporated herein by reference. 
    
    
     RELATED ART  
      In the manufacture or repair of products that include a sealed compartment, various methods have been used to determine how well the compartment is sealed, and where water or air intrusion (or extrusion) might occur. In the case of vehicles, for example, it is important to verify that water will not leak into the passenger compartment. Since visual inspection can be highly unreliable, certain vehicle manufacturers utilize spray booths for subjecting fully assembled vehicles to an intense water spray to ensure that vehicles shipped from the factory will not leak due to faulty or damaged seals. While this type of testing can be fairly reliable, it requires a worker to check for the presence of water in the cabin, and it is destructive in the sense that it can cause significant water intrusion in poorly sealed vehicles, or in vehicles where a window or door has been inadvertently left partially open, requiring significant expenditure of time and material for repairs due to water damage. Additionally, the spray booths are expensive to install and maintain, and cannot be easily duplicated at vehicle service and repair facilities.  
      In attempts to alleviate some of the problems associated with spray booths, some leak detection systems employ ultrasonic sensors to non-destructively detect leaks within vehicles. U.S. Pat. No. 6,983,642 entitled “System and Method for Automatically Judging the Sealing Effectiveness of a Sealed Compartment,” which is incorporated herein by reference, describes one such leak detection system. In this regard, at least one ultrasonic transmitter is placed within the passenger compartment of a vehicle and emits ultrasonic energy. Ultrasonic sensors on the outside of the vehicle are used to determine the levels of ultrasonic energy within a close proximity of the vehicle. Ultrasonic energy may escape from the vehicle through a leak causing an increased amount of ultrasonic energy external to the vehicle at or close to the location of the leak. Thus, by detecting the increased ultrasonic energy, a sensor can detect the presence of the leak.  
      Unfortunately, manufacturing an efficient and reliable leak detection system that utilizes non-destructive ultrasonic sensing capabilities can be difficult and expensive. Further, it is contemplated that a convenient location for a leak detection system is on or close to an assembly line of a vehicle manufacturer. Such an environment can be extremely noisy and, therefore, adversely affect the performance of the leak detection system. Moreover, better and less expensive leak detection systems and methods capable of non-destructively detecting leaks of sealed compartments, such as passenger compartments of vehicles, are generally desirable. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The disclosure can be better understood with reference to the following drawings. The elements of the drawings are not necessarily to scale relative to each other, emphasis instead being placed upon clearly illustrating the principles of the disclosure. Furthermore, like reference numerals designate corresponding parts throughout the several views.  
       FIG. 1  is a block diagram illustrating an exemplary leak detection system in accordance with the present disclosure.  
       FIG. 2  depicts a front view of an exemplary leak detection system, such as is depicted in  FIG. 1 .  
       FIG. 3  depicts a top view of the leak detection system depicted in  FIG. 2 .  
       FIG. 4  depicts a side view of the leak detection system depicted in  FIG. 2 .  
       FIG. 5  depicts a three-dimensional view of an exemplary support structure for the leak detection system depicted in  FIG. 2 .  
       FIG. 6  is a block diagram illustrating an exemplary computer system used in the leak detection system of  FIG. 2 .  
       FIG. 7  depicts a portion of the exemplary support structure depicted in  FIG. 5 .  
       FIG. 8  depicts the support structure of  FIG. 7  with panels removed to better illustrate an exemplary frame within the support structure.  
       FIG. 9  is a top view of an exemplary panel that may be attached to the frame of  FIG. 8  as depicted in  FIG. 7 .  
       FIG. 10  depicts an exemplary side view of the leak detection system of  FIG. 2  for one exemplary sample.  
       FIG. 11  depicts an exemplary side view of the leak detection system of  FIG. 2  for another sample.  
       FIG. 12  depicts an exemplary side view of the leak detection system of  FIG. 2  for yet another sample.  
       FIG. 13  depicts an exemplary side view of the leak detection system of  FIG. 2  for yet another sample.  
       FIG. 14  depicts a side view of a vehicle tested by the leak detection system of  FIG. 2  showing different regions corresponding to various ultrasonic sensors for a single sample.  
       FIG. 15  depicts a side view of the vehicle of  FIG. 14  showing different regions corresponding to different ultrasonic sensors for multiple samples.  
       FIG. 16  is a table illustrating an exemplary threshold profile for the vehicle of  FIG. 15 .  
       FIG. 17  depicts a side view of another vehicle tested by the leak detection system of  FIG. 2  showing different regions corresponding to different ultrasonic sensors for multiple samples.  
       FIG. 18  is a table illustrating an exemplary threshold profile for the vehicle of  FIG. 17 .  
       FIG. 19  depicts a three-dimensional view of an exemplary ultrasonic transmitter placed within a passenger compartment of a vehicle depicted in  FIG. 2 .  
       FIG. 20  depicts a back view of the transmitter depicted in  FIG. 19 .  
       FIG. 21  is a block diagram illustrating the transmitter depicted in  FIG. 19 .  
       FIGS. 22 and 23  depict flow charts that illustrate an exemplary methodology for testing a vehicle for leaks.  
       FIG. 24  is a block diagram illustrating an exemplary computer system used in the leak detection system of  FIG. 2 .  
       FIG. 25  depicts an exemplary graphical user interface used in the leak detection system of  FIG. 2 .  
       FIG. 26  is a block diagram illustrating a data storage and access device used in the leak detection system of  FIG. 2 .  
       FIG. 27  is a block diagram illustrating an exemplary network of the leak detection system of  FIG. 2 .  
       FIG. 28  is a block diagram illustrating an exemplary system for accessing leak detection data generated by a leak detection system, such as is depicted in  FIG. 1 .  
       FIG. 29  depicts a flow chart that illustrates an exemplary methodology for testing a vehicle for leaks. 
    
    
     DETAILED DESCRIPTION  
      The present disclosure generally pertains to systems and methods for reliably detecting leaks in sealed compartments, such as compartments within vehicles. In several embodiments of the present disclosure, an apparatus having a sealed compartment, such as a vehicle (e.g., automobile, airplane, etc.), is moved past an array of ultrasonic sensors. An ultrasonic transmitter is placed in the sealed compartment and emits ultrasonic energy as the apparatus is moved past the ultrasonic sensors. A leak can be automatically and non-destructively detected by analyzing data from the ultrasonic sensors.  
      For purposes of illustration, the systems and methods of the present disclosure will be described hereafter as detecting leaks within sealed compartments, such as passenger compartments or trunks, of vehicles (e.g., automobiles, aircraft, boats, etc.). It is to be understood, however, that the systems and methods of the present disclosure may be similarly used to detect leaks in other types of sealed compartments.  
      Note that the systems and methods of the present disclosure may be used to test compartments having either hermetic or non-hermetic seals. For example, a passenger compartment of an automobile is typically non-hermetic in that there typically exists at least some normal leakage in the passenger compartment even if the compartment and, in particular, the seals of the compartment are non-defective. In such embodiments, systems in accordance with the present disclosure can be configured to detect only leaks that are abnormal in the sense that they allow an excessive or greater than an expected or desired amount of leakage thereby making the compartment seal defective. For example, a leak in a vehicle that allows an unacceptable amount of water or air intrusion is abnormal, whereas any leak in a compartment designed in another example to be hermetically sealed is abnormal.  
       FIG. 1  depicts a leak detection system  30  that tests for abnormal compartment leaks in accordance with an exemplary embodiment of the present disclosure. The system  30  comprises an ultrasonic transmitter  33  that is placed within a compartment  36 , such as a passenger compartment of a vehicle (not specifically shown in  FIG. 1 ). The compartment  36  is moved past ultrasonic sensors  45  tuned to the frequency of the transmitter  33 . In one exemplary embodiment, the transmitter  33  emits ultrasonic energy at approximately 40 kilo-Hertz (kHz). An object sensing system  46  detects a location of the vehicle during the test, and ultrasonic sensors  45  detect ultrasonic energy that escapes from the compartment  36  as it is moved past the sensors  45 . Based on the ultrasonic energy detected by the sensors  45 , a test manager  50  determines whether the compartment  36  has any abnormal leaks. Further, by analyzing the data from the sensors  45  relative to the position of the vehicle compartment  36  during the test (as determined from data provided by the object sensing system  44 ), the test manager  50  identifies a location of each abnormal leak detected by the system  30 .  
       FIGS. 2-4  depict an exemplary embodiment of the leak detection system  30  in accordance with an exemplary embodiment of the present disclosure. The system  30  comprises a support structure  52  for supporting an array of ultrasonic sensors  45   a - p  mounted thereon. A three-dimensional view of the support structure  52  coupled to the sensors  45   a - p  is depicted in  FIG. 5 . In the embodiment depicted by  FIG. 2 , the support structure  52  is in the shape of an arch, and sixteen ultrasonic sensors  45   a - p  are coupled to the structure  52 . However, other shapes of the structure  52  and other numbers of ultrasonic sensors  45   a - p  are possible in other embodiments.  
      To test a passenger compartment  36  of a vehicle  59  for leaks, an ultrasonic transmitter  33  is placed within the passenger compartment  36 . Further, the vehicle  59  is positioned within close proximity of the ultrasonic sensors  45   a - p  (e.g., under the arch formed by the structure  52 ) such that, if the passenger compartment  36  has an abnormal leak, at least one ultrasonic sensor  45   a - p  can detect ultrasonic energy that exits through the leak. For example, the vehicle  59  may be passed through the arch formed by the structure  52  while the ultrasonic transmitter  33  in the passenger compartment  36  is emitting ultrasonic energy and while the sensors  45   a - p  are actively detecting ultrasonic energy. If the passenger compartment  36  of the vehicle  59  has an abnormal leak, then the sensor  45   a - p  closest to the leak will likely detect at least some of the ultrasonic energy that excessively escapes from the vehicle  59  through the leak. Thus, it is possible to detect the abnormal leak based on such sensor  45   a - p.    
      In this regard, the test manager  50  ( FIG. 1 ) is preferably in communication with each of the sensors  45   a - p  and determines whether the vehicle  59  has any abnormal leaks in its various compartments (e.g., passenger compartment, trunk, etc.) based on data from the sensors  45   a - p . The test manager  50  can be implemented in software, hardware, or a combination thereof. In one exemplary embodiment, as depicted in  FIG. 6 , the test manager  50 , along with its associated methodology, is implemented is software and stored within memory  61  of a computer system  63 .  
      Note that the test manager  50 , when implemented in software, can be stored and transported on any computer-readable medium for use by or in connection with an instruction execution apparatus, such as a microprocessor, that can fetch and execute instructions. In the context of this document, a “computer-readable medium” can be any means that can contain, store, communicate, propagate, or transport a program for use by or in connection with an instruction execution apparatus. The computer readable-medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor apparatus or propagation medium.  
      The exemplary embodiment of the system  63  depicted by  FIG. 6  comprises at least one conventional processing element  72 , such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the system  63  via a local interface  75 , which can include one or more buses. Furthermore, a user input device  77 , for example, a keyboard or a mouse, can be used to input data from a user of the system  63 , and a user output device  79 , for example, a printer or monitor, can be used to output data to the user.  
      The system  63  also comprises a communication interface  83  that enables the system  63  and, in particular, the test manager  50  to communicate with the transmitter  33  that is placed in the vehicle  59 . In one embodiment, the communication interface  83  is able to communicate wireless signals, such as wireless radio frequency (RF) signals, with the transmitter  33 , although non-wireless signals are also possible.  
      A sensor interface  85  is communicatively coupled to each of the ultrasonic sensors  45   a - p . For example, one or more conductive connections (not specifically shown) may extend from the sensor interface  85  to the sensors  45   a - p  to enable digital or analog communication between the interface  85  and the sensors  45   a - p . In an another embodiment, wireless signals may be communicated between the interface  85  and the sensors  45   a - p . The test manager  50  utilizes the interface  85  to receive data from the sensors  45   a - p , as will be described in more detail hereafter.  
      The system  63  further comprises an input/output (I/O) interface  87  that enables the system  63  to communicate with various external devices. For example, the I/O interface  87  may be communicatively coupled to components of the object sensing system  46  ( FIG. 1 ), as will be described in more detail hereafter. An optical scanner  88  may be used to input certain information, such as vehicle identification information, to the system  63 .  
      As shown by  FIGS. 2-5 , the support structure  52  has a plurality of interconnected panels  105  that are arranged to form a channel  107  extending underneath the structure  52  on a side facing the vehicle  59 . In the embodiment shown by  FIGS. 2-5 , a portion of each sensor  45   a - 45   p  is positioned within this channel  107 . For example,  FIG. 7  depicts an exemplary ultrasonic sensor  45   c . The sensor  45   c  has a housing  112  in which circuitry for sensing ultrasonic energy resides. In this regard, ultrasonic energy is received by a transducer  115  that converts the energy into electrical signals. The transducer  115  may be mounted on the housing  112  via a shock mount  117 . The transducer  115  is mounted such that it is positioned just outside of the periphery of the panels  105 . Circuitry within the housing  112  filters and processes the electrical signals from the transducer  115  to provide a measured value of the ultrasonic energy detected by the sensor  45   c  at the frequency emitted by the transmitter  33 . For each measured sample, the circuitry transmits data indicative of the measured ultrasonic energy to the test manager  50 .  
      Note that the panels  105  shield the transducer  115  from at least some ambient ultrasonic energy helping to acoustically isolate the sensor  45   c  from the environment in which the system  30  is placed. Acoustically isolating the sensor  45   c  from ambient noise helps to improve the sensor&#39;s performance and, in particular, the sensor&#39;s sensitivity to the ultrasonic energy emitted from the transmitter  33  located within the vehicle  59 . In general, to help prevent reverberations of ultrasonic energy within the channel  107  from affecting the performance of the sensors  45   c , it is generally desirable to mount the transducer  115  so that it is located just outside of the channel  107  and, therefore, the interior regions of the panels  105 . However, in various embodiments, it is possible for the transducer  115  to be positioned within the channel  107 , if desired. Each of the transducers  45   a - p  may be similarly or identically configured as sensor  45   c , and, as with sensor  45   c , the panels  105  may help to acoustically isolate each of the sensors  45   a - p.    
       FIG. 8  depicts the support structure  52  with the panels  105  removed for illustrating the exemplary configuration of the structure  52 . As shown by  FIG. 8 , the structure  52  comprises an inner frame  122  on which the sensors  45   a - p  and the panels  105  are mounted. Each end of the frame  122  is attached to a foot  124  having a flat bottom surface resting on a surface of the ground or floor. To help acoustically isolate the structure  52  and, in particular, sensors  45   a - p  from the surrounding environment, the material of the foot  124  on its bottom surface (i.e., contacting the surface of the ground or floor) is composed of an acoustic insulating material, such as rubber, that resists the transfer of energy or sound vibrations from the surface of the floor or ground to the frame  122 . By not bolting or otherwise affixing the feet  124  or other components of the structure  52  to the surface of the ground or floor on which the structure  52  is resting, acoustic isolation of the structure  52  can be improved by eliminating the introduction of acoustic vibration that might travel over couplers used to affix the structure  52  to the ground or floor surface. Note that conductive wires or cables enabling communication between the sensors  45   a - p  and the test manager  50  may be attached to and run along either the frame  122  or the panels  105 .  
      To test the vehicle  59  for leaks, the vehicle  59  is preferably passed through the arch defined by the structure  52  while the transmitter  33  in the vehicle  59  is emitting ultrasonic energy. In this regard, the vehicle  59  may be driven through the structure  52 , or a conveyor system, such as any of conventional conveyor systems of assembly lines found in vehicle manufacturing facilities may be used to pull the vehicle  59  through the structure  52 . For example,  FIG. 2  depicts movable tracks  132  on which the vehicle  59  is positioned. The tracks  132  may be moved by a motor (not shown) of a conveyor system to move the vehicle  59  through the arch defined by the structure  52 . Indeed, the structure  52  may be added to an existing assembly line at a vehicle manufacturing facility by placing the structure  52  at some point (e.g., the end) along an assembly line. The exemplary embodiment shown by  FIG. 2  depicts two tracks  132 , but other numbers of tracks may be used in other embodiments. For example, it is possible for the system  30  to use a single track wide enough so that each tire of the vehicle  59  can be positioned on the track.  
      Moreover, as the vehicle  59  passes through the structure  52 , the ultrasonic sensors  45   a - p  measure ultrasonic energy at the transmission frequency of the transmitter  33 . In this regard, each ultrasonic sensor  45   a - p  is tuned to the frequency of the transmitter  33  such that frequencies outside of the transmitted frequency range are filtered.  
      As an example,  FIG. 10  depicts an exemplary position of the vehicle  59  relative to the structure  52  when the first sample is taken. After this first sample, the vehicle  59  is moved such that it is further passed through the structure  52 , as depicted by  FIG. 11 , when the second sample is taken. Moreover, the vehicle  59  continues to move through the structure  52  as additional samples are taken. For example,  FIG. 12  depicts an exemplary position of the vehicle  59  relative to the structure  52  when the third sample is taken, and  FIG. 13  depicts an exemplary position of the vehicle  59  relative to the structure  52  when the fourth sample is taken. Further, additional samples are taken as the vehicle  59  moves through the structure  52  such that an abnormal leak at any point along the length of the vehicle compartment  36  can be successfully detected, as described herein.  
      By tracking the position of the vehicle  59  and, therefore, the compartment  36  relative to the sensors  45   a - p , the locations of abnormal leaks can be identified. In one exemplary embodiment, the object sensing system  46  ( FIG. 1 ) detects the location of the vehicle  59  and provides the test manager  50  with data indicative of such location. Thus, for each sample, the test manager  50  is aware of the sensors&#39; positions relative to the vehicle  59 . In fact, as will be described in more detail hereafter, the position of the vehicle  59  relative to the sensors  45   a - p  may be used by the test manager  50  to control when samples are to be taken. Moreover, if any sensor  45   a - p  has detected an abnormally high level of ultrasonic energy for any sample, then the test manager  50  determines that an abnormal leak exists in the vehicle  59  at an approximate location in close proximity to the sensor  45   a - p  that detects the abnormally high level of ultrasonic energy.  
      There are various techniques that may be used to track the vehicle&#39;s position relative to the sensors  45   a - p . In one exemplary embodiment, the object sensing system  46  comprises an object sensor  137  ( FIG. 3 ) and a distance sensor  139  ( FIG. 1 ). The object sensor  137  senses when the leading edge  138  (e.g., the front edge of the front bumper if the vehicle  59  is passing through the structure  52  in the orientation depicted by  FIGS. 2-4 ) of the vehicle  59  arrives at or in close proximity to the sensor  137 . For example, the object sensor  137  may be implemented as an optical sensor, such as an infrared sensor, that optically senses the presence of the vehicle  59 . In the embodiment depicted by  FIG. 3 , the object sensor  137  is an optical receiver that receives an optical signal continuously transmitted from an optical transmitter  141 . Thus, the object sensor  137  detects that the leading edge  138  of the vehicle  59  has reached reference line  142  when reception of the optical signal is interrupted (i.e., when the sensor  137  stops receiving the optical signal transmitted from transmitter  141 ). Other types of sensors for detecting the location of the vehicle  59  may be employed in other embodiments.  
      In addition, a distance sensor  139  detects movements of one of the tracks  132 , which preferably move in unison. As an example, the distance sensor  139  may comprise a shaft angle encoder or other known device commonly used for detecting movements of objects. Moreover, based on the data from the sensors  137  and  139 , the test manager  50  may determine the position of the vehicle  59  relative to the sensors  45   a - p . For example, once the vehicle  59  has been detected by the object sensor  137 , the test manager  59  can determine how far the leading edge  138  of the vehicle  59  has progressed by determining how far the a track  132  and, therefore, the vehicle  59  have moved since the detection of the leading edge  138  by the sensor  137 . Note that other techniques may be used to detect the position of the vehicle  59  relative to the sensors  45   a - p . As an example, an array of optical sensors, such as infrared sensors, may be positioned along the direction of movement of the vehicle  59 . Thus, as the vehicle  59  is moved through the structure  52 , the test manager  50  may determine the position of the vehicle  59  based on which of the optical sensors are detecting the presence of the vehicle  59 . Other types of sensors and techniques may be used to determine the movement of the vehicle  59 .  
      In one exemplary embodiment, the sensors  45   a - p  continuously measure ultrasonic energy during the test and transmit each measured value to the test manager  50 . Based on these values, the test manager  50  takes a sample of measured ultrasonic energy from the sensors  45   a - p  depending on the location of the vehicle  59  relative to the sensors  45   a - p . In this regard, to facilitate the testing process, the sensors  45   a - p  are arranged in a line, represented as reference line  145  ( FIG. 3 ), orthogonal to the direction of motion of vehicle  59 . Thus, it is assumed that each sensor  45   a - p  takes its measurements along the line  145 . However, for other embodiments, the sensors  45   a - p  can be arranged differently.  
      The test manager  50  is configured to take samples at specified distances along the length of the vehicle  59 . For example, for illustrative purposes, assume that the test manager  50  is configured to take a sample every 12 inches (1 foot) along the length of the vehicle  59 . In such an embodiment, the test manager  50  may take the first sample once the vehicle  59  has reached the reference line  145 . Referring to  FIG. 3 , the test manager  50  may determine when this has occurred by subtracting the distance (a) that the vehicle  59  has moved from line  142  (i.e., since detection of the vehicle  59  by sensor  137 ) from the distance (b) of the sensor  137  from the sensors  45   a - p  (i.e., from line  145 ). Indeed, the test manager  50  can determine when to take samples according to the following formula: 
 
 a−b= 12( c− 1), 
 
 where a and b are expressed in inches and where c is the sample number (i.e.,  1  for the first sample,  2  for the second sample,  3  for the third sample, etc.). Moreover, when the vehicle  59  has reached line  145 , the above equation is true for the first sample (i.e., c= 1 ). At this time, the test manager  50  takes the first sample by receiving and storing each measured value from each sensor  45   a - p . Note that a “sample” as used herein is defined by a measured value of ultrasonic energy from each sensor  45   a - p  such that the data defining each sample may be analyzed to determine the amount of ultrasonic energy detected by any of the sensors  45   a - p  at the time of the sample. Note that the sample data  146  in memory  61  of  FIG. 6  represents the sample values stored by the test manager  50  during the testing process. 
 
      After taking the first sample, c is incremented by one, and the test manager  59  takes the next sample (i.e., sample  2 ) when the above equation is again true. Thus, the test manager  59  takes the second sample when the leading edge  138  of vehicle  59  has moved 12 inches past line  145 , and the test manager  59  takes the third sample when the leading edge  138  of vehicle  59  has moved 24 inches past line  145 . By continuing to take samples in this manner, a sample is taken every 12 inches along the length of the vehicle  59 . It should be noted that the foregoing example has been provided for illustrative purposes, and there are an infinite number of ways that samples of the vehicle  59  may be taken in other embodiments.  
      As an example, the value b may be eliminated from the algorithm such that a sample is taken according to the formula: 
 
 a= 12( c− 1), 
 
 Using this methodology may change the relative position of the vehicle  59  for each sample. In addition, it is unnecessary for the entire length of the vehicle  59  or compartment  39  to be tested, and it is possible for the distance between samples to be varied. For example, it is unnecessary for each sample to occur the same distance after the last sample. In addition, other distances are possible in other embodiments. For example, to provide more precise leak location information, the vehicle  59  may be sampled (e.g., about every 1 inch) such that the distance between samples is less. 
 
      In one exemplary embodiment, vehicle data  130  ( FIG. 6 ) stored in the memory  61  of the test manager  50  associates each sensor  45   a - p  with a respective threshold for each sample. The threshold associated with a sensor  45   a - p  is set such that, if the ultrasonic energy measured by the sensor  45   a - p  for the sample exceeds the associated threshold, then an abnormal leak is present in the vehicle  59 . Moreover, as described above, for each sample, the test manager  50  stores a measured value from each sensor  45   a - p  at the time of the sample. For each such value received from a sensor  45   a - p , the test manager  50  compares the value to the sensor&#39;s associated threshold. If the value exceeds the threshold, then the test manager  50  determines that an abnormal leak is present in the vehicle  59 . Exemplary techniques for locating the detected leak within the vehicle  59  will be described in more detail hereinbelow.  
      In this regard, for each sample taken by the sensors  45   a - p , each sensor  45   a - p  corresponds to a different area around the perimeter of the vehicle  59 . If a vehicle compartment leak is within or close to this corresponding area, then the sensor  45   a - p  likely detects an amount of ultrasonic energy that exceeds the sensor&#39;s associated threshold defined by the data  130 .  
      As an example, assume that the vehicle  59  is positioned relative to the structure  52  as depicted by  FIG. 4 . In such an example, regions  141   a - f  ( FIG. 14 ) respectively correspond to sensors  45   a - f . In particular, region  141   a  ( FIG. 14 ) corresponds to sensor  45   a , and region  141   b  corresponds to sensor  45   b . In addition, region  141   c  corresponds to sensor  45   c , and region  141   d  corresponds to sensor  45   d . Further, region  141   e  corresponds to sensor  45   e , and region  141   f  corresponds to sensor  45   f . In general, a region “corresponds” to a sensor if the sensor is positioned such that its measurement is affected the most (relative to the measurements of other sensors) by ultrasonic energy emitted from such region. Thus, if an abnormal leak exists in a particular region, then the sensor affected the most by the ultrasonic energy escaping through the abnormal leak “corresponds” to the particular region.  
      There are various factors that affect how much ultrasonic energy from a source, such as an abnormal leak, is received by an ultrasonic sensor. One well-known factor is the distance of the sensor from the source since ultrasonic energy can be attenuated as it travels, particularly in noisy environments where ambient noise may cancel or interfere with portions of the ultrasonic energy to be detected. In general, each sensor  45   a - 45   p  is located closer to its corresponding region as compared to the other sensors of the system  30 . For example, region  141   b  is located closest to sensor  45   b  as compared to the other sensors  45   a  and  45   c - p , and region  141   c  is located closest to sensor  45   c  as compared to other sensors  45   a - b  and  45   d - p . However, as between any of the sensors  45   a - p  and its corresponding region, it is possible for another sensor to be located closer to such region.  
      For at least some ultrasonic sensors, another well-known factor affecting how much ultrasonic energy from a source is received by the sensor is the orientation of the sensor relative to the source or, in other words, the sensor&#39;s directivity. In this regard, it is well-known that an ultrasonic sensor can be directional in that it receives ultrasonic energy more efficiently in certain directions. For a respective sensor, a direction at which ultrasonic energy is most efficiently received by the sensor is referred to herein as an “axis of maximum reception” for the sensor. Thus, for a given ultrasonic signal, a sensor will generally measure the greatest amount of ultrasonic energy from the signal if such signal is traveling along the sensor&#39;s axis of maximum reception. In general, the greater that the signal&#39;s angle of travel deviates from the sensor&#39;s axis of maximum reception, the less efficient is the sensor&#39;s reception of such signal.  
      As an example, refer to  FIG. 34 , which depicts an exemplary sensor  45  that may be used to implement any of the sensors  45   a - p . As shown by  FIG. 34 , the sensor  45  has an axis of maximum reception  171 . The sensor  45  detects the greatest amount of ultrasonic energy from a signal if the signal is traveling toward the sensor  45  along the axis of maximum reception  171 . The received strength of an ultrasonic signal generally decreases as the signal&#39;s angular direction of travel moves further from the axis of maximum reception  171  and as the distance of the source of the signal moves further from the sensor.  
      Moreover, the reference lines  173  generally define the half power point boundary for the sensor  45 . A signal at any point within the area, referred to herein as the sensor&#39;s “area of reception,” defined by the half power point boundary represented by lines  173  experiences less than a 3 decibel loss, as measured by the sensor  45 , whereas a signal at any point outside of such area of reception experiences a loss of 3 dB or greater. In other words, the actual signal strength of a signal at any point within the sensor&#39;s area of reception is within 3 dB of the value measured by the sensor  45 , and the actual signal strength of a signal at any point outside of the sensor&#39;s area of reception is greater than 3 dB of the value measured by the sensor  45 . For example, the measured signal strength for a signal communicated at an angle greater than an angle, α, from the axis of maximum reception  171  is at least 3 dB less than its actual signal strength. Note that  FIG. 34  is a two-dimensional illustration of the half power point boundary, and this boundary is actually three-dimensional (e.g., conical) in shape. The half power point boundary is well-known to those skilled in the art, and the axis of maximum reception  171  usually passes through the center of the cone defined by the half power point boundary.  
      To increase a sensor&#39;s sensitivity to an abnormal leak in the sensor&#39;s corresponding region  141   a - p  of the vehicle  59 , the sensor&#39;s corresponding region  141   a - p  of the vehicle  59  for a given sample is preferably located within the sensor&#39;s area of reception. However, depending on signal strengths and ambient noise levels, it is possible for a sensor&#39;s corresponding region of the vehicle  59  to be located outside of the sensor&#39;s area of reception.  
      If the sensors  45   a - p  are configured as described above such that each sensor  45   a - p  has an axis of maximum reception  171 , as illustrated by  FIG. 34 , then the sensors  45   a - p  are oriented such that the axis of maximum reception  171  of each respective sensor passes through the center of the sensor&#39;s corresponding region for a given sample. Thus, for example, the axis of maximum reception  171  of sensor  45   b  passes through the center of region  141   b , the axis of maximum reception  171  of sensor  45   c  passes through the center of region  141   c , and so forth. However, it is possible for the axis of maximum reception  171  for a particular sensor  45   a - p  to be directed to a location other than the center of the sensor&#39;s corresponding region in other embodiments without departing from the principles of the present disclosure.  
      Moreover, if any ultrasonic energy escapes through an abnormal leak in a given region, then the corresponding sensor  45   a - p  is oriented such that its measurement will likely be affected the most by such ultrasonic energy relative to those of the other sensors  45   a - p . In this regard, the region&#39;s corresponding sensor should detect the greatest amount of the ultrasonic energy that is passing through the abnormal leak.  
      Further, if a leak is present in any of the regions  141   a - f , then the thresholds are preferably defined such that at least the corresponding sensor  45   a - f  will detect an amount of ultrasonic energy exceeding the sensor&#39;s associated threshold defined by the data  130 . For example, if an abnormal leak is within region  141   d , then the corresponding sensor  45   d  preferably detects an abnormally high amount of ultrasonic energy (e.g., the measured value from sensor  45   d  exceeds the threshold associated with this sensor  45   d ). Thus, by comparing the value from sensor  45   d  indicative of the amount of sensed ultrasonic energy, the test manager  50  can detect the presence of the leak.  
      Note that an abnormal leak in a particular region  141   a - f  may cause multiple thresholds to be exceeded. For example, ultrasonic energy passing through the leak described above as being within region  141   d  may result in significant increases in the ultrasonic energy being detected by, not only the corresponding sensor  45   d , but also by the sensors  45   c  and  45   e  corresponding to the adjacent regions  141   c  and  141   e , respectively. Thus, due to the leak in such an example, the amount of ultrasonic energy detected by sensor  45   c  may exceed the threshold associated with sensor  45   c  even though no leak actually exists in the corresponding region  141   c . Further, due to the foregoing exemplary leak in region  141   d , the amount of ultrasonic energy detected by sensor  45   e  may exceed the threshold associated with sensor  45   e  even though no leak actually exists in the corresponding region  141   e.    
      However, it is likely that the leak will have a greater effect on the sensor  45   d  corresponding to the region  141   d  in which the leak is present. Thus, if the thresholds are appropriately set in the instant example, as will be described in more detail hereafter, it is likely that the leak will cause the value from sensor  45   d  to exceed the threshold associated with this sensor  45   d  by a greater extent as compared to respective differences between the values from sensors  45   c  and  45   e  and the thresholds associated with these sensors  45   c  and  45   e . Accordingly, by analyzing the extent to which the thresholds associated with sensors  45   c - 45   e  are exceeded, it is possible for the test manager  50  to correctly determine that the leak is within region  141   d.    
      For example, if the difference between the sample value from sensor  45   d  and the threshold associated with sensor  45   d  is significantly greater than the differences between the sample values from sensor  45   c  and  45   e  and the associated thresholds for these sensors  45   c  and  45   e , then the test manager  50  can determine that a leak only exists in region  141   d . In one example, the test manager  50  determines the percentage that each threshold is exceeded and bases its analysis on such percentages rather than the absolute differences between sample values and thresholds. There are various ways that measurements for adjacent regions can be analyzed in order to pinpoint the areas of abnormal leaks.  
      However, it should be noted that, in many instances, a leak will cause only the sensor  45   a - p  corresponding to the region of the leak to detect a significantly increased amount of ultrasonic energy. In such situations, the region of the leak can be easily identified without comparing the differences between the sample values and thresholds of adjacent regions. Further, it is unnecessary for the test manager  50  to pinpoint leaks. For example, the test manager  50  may simply indicate which sample values exceeded their associated thresholds, and this data may be later analyzed to determine the locations of leaks. In such an example, the test manager  50  may provide an output indicating the difference between each sample value and its associated threshold. Exemplary outputs provided by the system  30  are described in more detail hereafter.  
      It should be noted that  FIG. 14  only shows the regions  141   a - f  corresponding to sensors  45   a - f  for a particular sample. Other regions similarly correspond to the other sensors  45   g - p  for the same sample. For example, sensors  45   g - j  may correspond to regions on the top surface (i.e., roof) of the vehicle  59 , and sensors  45   k - p  may correspond to regions on the side of the vehicle  59  opposite of that shown by  FIG. 14 . Thus, if a leak is present on either the driver or passenger side of the vehicle  59  or, alternatively, on top of the vehicle  59 , then the leak can be detected by at least one of the sensors  45   a - p . Note that region  141   a  is not substantially aligned with any portion of the vehicle  59  depicted by  FIG. 14 . Thus, it is unlikely that the sensor  45   a  corresponding to region  141   a  will ever detect a significant amount of ultrasonic energy from the transmitter  33  in the vehicle  59  since region  141   a  is not likely to have a leak. However, for other models of vehicles, particularly ones that sit lower to the ground, the region  141   a  may be aligned with such a vehicle to a greater extent such that monitoring of the region  141   a  via the corresponding sensor  45   a  is more useful to the testing process.  
       FIG. 15  depicts exemplary corresponding regions for the sensors  45   a - f  for each sample taken by the sensors  45   a - f  as the vehicle  59  is passing through the structure  52 . In particular,  FIG. 15  depicts regions segmented into different columns  141 - 156  and rows a-f. Each region within the same column  141 - 156  corresponds to a respective ultrasonic sensor for the same sample, and each region within the same row a-f corresponds to the same ultrasonic sensor for a respective sample. For example, for the first sample, such as when the vehicle  52  is in the position depicted by  FIG. 10 , regions  142   a - f  respectively correspond to sensors  45   a - f  similar to how regions  141   a - f  correspond to sensors  45   a - f  in  FIG. 14 .  
      Note that regions within the same row are sampled by the same sensor during different sampling periods. For example, sensor  45   f  samples region  142   f  during the first sampling period, and sensor  45   f  samples region  143   f  during the second sampling period. Further, the sensor  45   f  samples other regions of the same row f during other sampling periods. Each of the regions in the same row is sampled when the axis of reception  171  of the corresponding sensor passes through the region. Thus, if an abnormal leak is present in a particular region, then the corresponding sensor would likely be affected the most by ultrasonic energy passing through the leak during the sampling period that the sensor&#39;s axis of reception  171  passes through the region. For example, in the exemplary embodiment indicated by  FIG. 15 , the axis of reception of the sensor  45   d  passes through region  141   d  in the ninth sampling period (i.e., for the ninth sample). Thus, if an abnormal leak is present within region  141   d , such leak should be detected at least in the ninth sampling period when the region  141   d  is being sampled by the sensor  45   d.    
      Note that the example shown by  FIG. 15  is consistent with the previously described sampling methodology in which a sample is taken along the length of the vehicle  59  every 12 inches or 1 foot. If such a methodology is used to take samples resulting in the segmentation of the regions depicted by  FIG. 15 , then each region shown by  FIG. 15  may be 1 foot in width (in the x-direction) such that the center of each region is (n−1) feet from the leading edge of the vehicle  59 , where n is the corresponding sample number. For example the centers of regions  142   a - f  may be at the leading edge  138  of the vehicle  59 , and the centers of the regions in column  143  may be one foot from the leading edge  138  of the vehicle  59 . Indeed, in the embodiment depicted by  FIG. 15 , each sensor  45   a - p  is preferably aligned with the center of its corresponding region for a given sample. For example, for sample number  9 , sensor  45   d  is aligned with the center of its corresponding region  141   d  and is closest to this region  141   d  as compared to the other ultrasonic sensors.  
      As described above, vehicle data  130  associates a respective threshold for each of the sensors  45   a - p  on a per sample basis. In this regard, each threshold is preferably defined to approximately equal the expected amount of ultrasonic energy that the threshold&#39;s associated sensor  45   a - p  is to detect if the vehicle  59  being tested is free of abnormal leaks (i.e., if the seal of compartment  36  is non-defective). Thus, if a threshold is exceeded by the sample value from the associated sensor  45   a - p , then it is likely that the vehicle  59  has an abnormal leak. Further, as described above, a detected leak is likely close to or in the sensor&#39;s corresponding region. For example, as described above, region  141   d  is associated with sensor  45   d  for sample number  9  (i.e., the ninth sample). Thus, if the value from sensor  45   d  for sample number  9  (i.e., when the sensor  45   d  is aligned with the center of region  141   d ) exceeds the threshold associated with sensor  45   d  for this sample, then there is likely an abnormal leak close to or in the region  141   d.    
       FIG. 16  depicts an exemplary table of thresholds that may be defined by the data  130  ( FIG. 6 ) for the sensors  45   a - p  on a per sample basis. As shown by  FIG. 16 , each sensor  45   a - p  is associated with a different threshold for a different sample. For example, sensor  45   d  is associated with the threshold value of 10.0 for the first sample (i.e., sample  1 ). Thus, for the first sample, the sample value measured by the sensor  45   d  is compared to the threshold value of 10.0 by the test manager  50 . However, for the ninth sample, the sample value measured by the sensor  45   d  is compared to the threshold value of 15.0 by the test manager  50 . The result of this comparison likely indicates whether a leak exists in the region  141   d  corresponding to sensor  45   d  for sample  9 . Thus, the data  130  effectively associates the threshold    15 . 0   , not only with sensor  45   d  for sample  9 , but also with region  141   d . Indeed, the data  130  indicates that this threshold should be exceeded if an abnormal leak exists in the region  141   d.    
      As can be seen by comparing  FIG. 16  to  FIG. 15 , the thresholds indicate an expected amount of ultrasonic energy to be detected by the associated sensors  45   a - p  for a leak-free vehicle  59 . For example, threshold values are low if they are associated with a sensor  45   a - p  that is monitoring a region not substantially aligned with the vehicle compartment  36  being tested. As a mere example, the threshold associated with sensor  45   a  for sample  1  is relatively low (i.e., 10.0). Moreover, for this sample, the sensor  45   a  corresponds to region  142   a , which (as shown by  FIG. 13 ) is not aligned with the vehicle  59 . Therefore, for sample  1 , the sensor  45   a  should not detect a relatively high amount of ultrasonic energy. Region  145   d  is aligned with the vehicle  59  but not with the passenger compartment  36  being tested. Thus, the threshold associated with the sensor  45   d  corresponding to region  145   d  for sample number  4  is low indicating that sensor  45   d  should not detect a relatively high amount of ultrasonic energy.  
      Further, the threshold associated with sensor  45   c  for sample  6  is low (i.e., 10.0). For this sample, the sensor  45   c  corresponds to region  147   c , which (as shown by  FIG. 15 ) is aligned with the compartment  36  but there are no seams in this region  147   c . Thus, unless a leak exists in or close to this region  147   c , the sensor  45   c  should not detect a relatively high amount of ultrasonic energy. If a high amount of energy (i.e., an amount above 10.0) is detected by sensor  45   c  for this sample, then the test manager  50  may detect the presence of an abnormal leak close to or within the region  147   c.    
      However, the threshold associated with sensor  45   d  for sample  9  is relatively high (i.e., 15.0). For this sample, the sensor  45   d  corresponds to region  141   d , which (as shown by  FIG. 15 ) is aligned with a portion of the vehicle  59  that has a seam  153 . Even without an abnormal leak in region  141   d , a relatively high amount of ultrasonic energy may escape through this seam  153 , and the foregoing threshold may, therefore, be set higher than other thresholds as shown by  FIG. 16 . Indeed, in the instant example, the sample value determined by the sensor  45   d  for sample  9  can reach as high as 15.0 without the test manager  50  detecting an abnormal leak based on this sample value.  
      Note that the thresholds defined by the data  130  may be empirically determined. For example, to initialize the thresholds, a vehicle of the same type (e.g., model) to be tested that is known or believed to be free of abnormal leaks may be passed through the structure  52 , as described above, while the transmitter  33  in the vehicle is emitting ultrasonic energy and while the sensors  45   a - p  are actively sensing ultrasonic energy. Moreover, the sample values measured by the sensors  45   a - p  for samples  1 - 16  may then be used to define the thresholds. If desired, the sample values from multiple vehicles of the same or similar type (e.g., model) may be averaged to define the thresholds.  
      Moreover, to have the thresholds tailored to the type of the vehicle being tested so that more accurate test results are possible, it may be desirable to define multiple sets of thresholds for different vehicle types (e.g., models). In this regard, differences in the designs of different types of vehicles may result in variations in the amount of ultrasonic energy that normally escapes from vehicles free of abnormal leaks. For example, for a given model of a sports utility vehicle (SUV), such as the one depicted in  FIG. 15 , a certain amount of ultrasonic energy may normally escape from the vehicle  59  along the seam  153  between the front door and the rear door even when there is no abnormal leak along this seam  153 . Moreover, as described above, the thresholds associated with regions  141   b - f  along the seam  153  are based on this expected amount of ultrasonic energy escaping along the seam  153 . However, the normal amount of ultrasonic energy that escapes from the corresponding seam between the front and rear doors of another vehicle model, such as a model of a car, may be quite different than the amount expected for the SUV. Thus, it may be desirable to define, for the car, different thresholds for the regions along the seam between the front and rear doors as compared to the thresholds for the aforementioned regions of the SUV of  FIG. 15  along the seam  153 .  
      To better illustrate the foregoing, refer to  FIGS. 17 and 18 .  FIG. 17  depicts exemplary sampling regions for a car  159 , similar to the diagram of  FIG. 15  for the SUV  59 . In this regard,  FIG. 17  depicts exemplary corresponding regions for the sensors  45   a - f  for each sample taken as the car  159  is passing through the structure  52 . In particular,  FIG. 17  depicts regions segmented into different columns  141 ′- 156 ′ and rows a′-f′. Similar to  FIG. 15 , each region within the same column  141 ′- 156 ′ corresponds to a respective ultrasonic sensor for the same sample, and each region within the same row a′-f′ corresponds to the same ultrasonic sensor for a respective sample.  
      Further,  FIG. 18  depicts, for the car  159 , an exemplary table of thresholds that may be defined by the data  130  for the sensors  45   a - f  on a per sample basis, similar to how  FIG. 16  depicts an exemplary table of thresholds for the SUV  59  of  FIG. 15 . According to the diagram of  FIG. 17 , the sensor  45   d  corresponds to the region  141   d ′ aligned with the seam  153 ′. Thus, if an abnormal leak is located in this region  141   d ′, then such a leak should be detected based on the data output by the sensor  45   d  for sample  9 . As can be seen by comparing  FIGS. 17 and 18 , the threshold used to compare to this sample value output by the sensor  45   d  is 13.0. This threshold is different than the one used for the region  141   d  of the SUV  59  aligned with the seam  153 . Indeed, by comparing  FIGS. 16 and 18 , it can be seen that different threshold profiles can be defined for different vehicle types such that the thresholds used for a particular vehicle are tailored to the vehicle&#39;s type to account for the fact that different vehicle model or styles may have different sealing characteristics.  
      Thus, if the system  30  is being used to test an SUV, similar to the one depicted by  FIG. 15 , then the test manager  50  can be configured to use the thresholds depicted by  FIG. 16 . However, if the system  30  is being used to test a car, similar to the one depicted by  FIG. 17 , then the test manager  50  can be configured to use the thresholds depicted by  FIG. 18 . Moreover, the vehicle data  130  may store both of the threshold profiles shown by  FIGS. 16 and 18 , and the test manager  50  may select the appropriate one during testing based on the type of vehicle being tested. To enable the test manager  50  to make the appropriate selection, the test manager  50  may receive an input, such as a vehicle identification number (VIN), from a user or other source indicating the type of vehicle being tested.  
      Note that different threshold profiles may be defined for various category levels. For example, a different threshold profile may be defined for the categories of “truck,” “car,” and “SUV.” In such an example, a first threshold profile may be used for all trucks, a second threshold profile may be used for all cars, and a third threshold profile may be used for all SUVs. However, in other examples, any of the categories may be further divided or different categories may be used altogether. As a mere example, a different threshold profile may be used for different SUVs depending on the model of SUV being tested. For example, a first threshold profile may be used for a Ford Explorers™, whereas a second threshold profile may be used for a Toyota Pathfinder™. Moreover, the different threshold profiles may be categorized in any desired manner without departing from the principles of the present disclosure.  
      However, the vehicle identifier received by the test manager  50  for enabling selection of the appropriate threshold profile preferably includes sufficient type information to identify the threshold profile for the vehicle to be tested. For example, if the thresholds are categorized according to just three categories (e.g., truck, car, and SUV), then the vehicle identifier may simply indicate whether the vehicle to be tested is a truck, car, or SUV. However, if the threshold profiles are categorized according to whether the vehicle is a particular type (e.g., model) of truck, car, or SUV, then the vehicle identifier preferably indicates sufficient information to identify the particular type (e.g., model) of truck, car, or SUV being tested. Thus, the vehicle identifier provided to the test manager  50  is preferably of sufficient specificity to enable the test manager  50  to select the appropriate threshold profile for the vehicle being tested.  
      Note that is it is common for all vehicles to be respectively assigned a vehicle identification number (VIN) that uniquely identifies each vehicle from all other vehicles. In one embodiment, the VIN of the vehicle being tested is used to select the appropriate threshold profile. For example, a user may enter an input indicative of the VIN. Alternatively, the VIN may alternatively be captured (e.g., via optical scanning) by an electronic device (e.g., the scanner  88  of  FIG. 6 ) and transmitted to the test manager  50 .  
      In such an example, the vehicle data  130  preferably includes sufficient information for correlating the VIN with the appropriate threshold profile to be used for the testing, and the test manager  50  uses this information to select the appropriate threshold profile. For example, the data  130  may include a list of VINs, and each VIN may be correlated with the respective threshold profile to be used for testing the vehicle identified by the VIN. Alternatively, the data  130  may correlate vehicle model identifiers with different threshold profiles. In this regard, it is well-known for a portion of a vehicle&#39;s VIN to identify the model of the vehicle. Thus, vehicles of the same model have the same model identifier included within their VINs. For each VIN, the test manager  50  may be configured to extract the vehicle&#39;s model identifier from the VIN and select the threshold profile correlated with the extracted model identifier. Thus, the same threshold profile is used to test vehicles of the same model, but different threshold profiles may be used to test other models. Various other techniques for selecting the appropriate threshold profile to be used to test a vehicle may be employed in other embodiments.  
      In addition to tailoring the threshold profile to the type of vehicle being tested, the operation of the transmitter  33  can also be tailored to the type of vehicle being tested, as will be described in more detail hereinbelow, in order to improve test results. In this regard,  FIGS. 19 and 20  depict a transmitter  33  in accordance with an exemplary embodiment of the present disclosure. The transmitter  33  has a plurality of transducers  181   a - h . Each of the transducers  181   a - h converts electrical energy into ultrasonic energy and transmits converted ultrasonic energy in a different direction as compared to the other transducers. In the exemplary embodiment depicted by  FIGS. 19 and 20 , the transmitter  33  has eight transducers  181   a - h , which are respectively pointed in and transmit ultrasonic energy in different directions. In this regard, at least one respective transducer  181   a - h is pointed in and transmits ultrasonic energy in each of the x, −x, z, −z, and y-directions. Thus, the direction of transmission for each respective transducer  181   a - h is either parallel or orthogonal to the direction of transmission of the other transducers. For example, the direction of transmission of transducers  181   d  and  181   h  is in the −x direction, which is orthogonal to the directions of transmission of transducers  181   a ,  181   b ,  181   e , and  181   g  (i.e., y, z, and −z directions). Further, the direction of transducers  181   d  and  181   h  is opposite to the direction of transmission of transducers  181   c  and  181   f  (i.e., x direction). However, other numbers of transducers and other directions of transmission are possible in other embodiments.  
      In some instances, depending on the acoustic characteristics of the vehicle  59  being tested, all of the transducers  181   a - 181   e  may be configured to continuously emit ultrasonic energy at a constant transmission power. As used herein, the “transmission power” refers to the power level of ultrasonic energy as it leaves the transducer that is transmitting it. Transmitting ultrasonic energy continuously in so many different directions can increase the probability that, if there is an abnormal leak, significant ultrasonic energy will be directed toward and pass through the leak, thereby enabling detection of the leak by the test manager  50 . Such a mode of operation for the transmitter  33  will be referred to hereafter as the “normal mode” of operation.  
      However, depending on the acoustic characteristics of the passenger compartment  36  in which the transmitter  33  is placed, it is possible for the ultrasonic energy to be redirected via the interior of the compartment  36  such that at least some of the ultrasonic energy interferes or cancels some of the ultrasonic energy within the compartment  36 . Thus, the total amount of ultrasonic energy may be decreased possibly reducing the amount of ultrasonic energy that would otherwise pass through an abnormal leak. Accordingly, detection of the abnormal leak may be more difficult. In such situations, it may be desirable to reduce or eliminate the amount of ultrasonic energy emitted by at least one of the transducers  181   a - h.    
      For example, depending on the acoustic characteristics of the interior of vehicle  59 , the transmission power of one or more of the transducers  181   a - h may be adjusted (e.g., increased or decreased) to provide a more optimal testing environment. The adjustment may be permanent for the test being performed on the particular vehicle  59 , or it may be temporary. For example, the transmission power of one or more transducers  181   a - h may be reduced for the duration of the test being performed on the vehicle  59 . As a further example, if it is determined that ultrasonic energy from transducer  181   a  interferes with or cancels ultrasonic energy from transducer  181   b , then transducer  181   a  may be deactivated during the test such that this transducer  181   a  does not emit any ultrasonic energy. In another example, the transmission power of transducer  181   a  can be intermittently reduced according to a predefined algorithm. For example, one or more of the transducers  181   a - h may be configured to intermittently stop emitting ultrasonic energy such that at any given instant only a specified number (e.g., one) transducers  181   a - h are emitting ultrasonic energy. There are an infinite number of ways that the emission of ultrasonic energy by the transmitter  33  can be controlled.  
      In one exemplary embodiment, the operation of the transducers  181   a - h is controlled by a transmit manager  185  ( FIG. 21 ), which can be implemented in software, hardware, or a combination thereof. In one exemplary embodiment, as depicted in  FIG. 21 , the transmit manager  185 , along with its associated methodology, is implemented in software and stored within memory  186  of the transmitter  33 . Note that the transmit manager  185 , when implemented in software, can be stored and transported on any computer-readable medium for use by or in connection with an instruction execution apparatus, such as a microprocessor, that can fetch and execute instructions.  
      The exemplary embodiment of the transmitter  33  depicted by  FIG. 21  comprises at least one conventional processing element  189 , such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the transmitter  33  via a local interface  191 , which can include one or more buses. Furthermore, a user input device  193 , such as one or more buttons, for example, can be used to input data from a user of the transmitter  33 , and a user output device  195 , such as a liquid crystal display (LCD), for example, can be used to output data to the user. The transmitter  33  also comprises a power supply  198 , such as a battery, for example, to power the transmitter components. Further, a communication interface  199  enables the transmitter  33  to communicate with the system  63  of  FIG. 6 . In one embodiment, the communication interface  199  communicates wireless signals with the system  63 , although non-wireless signals may be communicated in other embodiments. As shown by  FIG. 21 , the transducers  181   a - h may be interfaced with other components of the transmitter  33  via the local interface  191 .  
      To conserve the power supply  198 , the transmit manager  185  is configured to place the transmitter  33  in a sleep state until testing of the vehicle  59  begins or is about to begin. Thus, the transmit manager  185  powers down various components, such as the transducers  181   a - h , for the sleep state. In one embodiment, a command to wake the transmitter  33  to indicate the imminent start of testing is received via communication interface  199 , as will be described in more detail hereafter. Thus, the communication interface  199  and components for implementing the test manager  185  are sufficiently powered during the sleep state to enable messages to be received by the test manager  185  via the communication interface  199 .  
      In one embodiment, the test manager  50  ( FIG. 6 ) determines when testing of the vehicle  59  is to begin based on the object sensor  137 . In this regard, when the sensor  137  detects the presence of the vehicle  59 , the test manager  50  transmits a wake command to the transmitter  33  via interfaces  83  ( FIG. 6 ) and  199  ( FIG. 21 ). In response, the transmit manager  185  wakes the other components of the transmitter  33 , such as the transducers  181   a - h that are to emit ultrasonic energy during testing.  
      In this regard, the vehicle data  130  stored in the system  63 , in addition to storing the threshold profile to be used for the type of vehicle  59  being tested, also stores information indicative of the desired transmit profile to be used for the type of vehicle  59  being tested. The “transmit profile” refers to the desired manner that the transducers  181   a - h are to be operated during testing. For example, as described above, it may be desirable to adjust the transmission power of one or more of the transducers  181   a - h such that it transmits ultrasonic energy differently as compared to the normal mode of operation for transmitter  33 .  
      Moreover, based on the vehicle identifier received by the test manager  50 , the test manager  50 , as described above, selects the appropriate threshold profile for the identified vehicle  59  as indicated by the vehicle data  130  and uses this threshold profile to test the vehicle  59 . However, the test manager  50  also uses the vehicle identifier to select the appropriate transmit profile for the transmitter  33  as indicated by the vehicle data  130 . The test manager  50  then transmits information indicative of the selected transmit profile to the transmitter  33  via interfaces  83  and  199 . Based on this information, the transmit manager  185  controls the transducers  181   a - h such that they operate according to the selected transmit profile during testing. Accordingly, the manner in which the transducers  181   a - h  operate can be tailored to the type of vehicle  59  being tested. For example, all vehicles of a particular type (e.g., model) can be tested according to the same transmit profile while vehicles of a different type can be tested according to a different transmit profile.  
      Note that the transmit profile to be used for a particular vehicle  59  may be determined based on empirical data. For example, to determine the appropriate transmit profile for a particular vehicle, a similar styled vehicle may be tested by the system  30  multiple times using different transmit profiles for each of the tests. For example, all of the transducers  181   a - h may be operated to continuously emit ultrasonic energy at a constant transmit power for one test, and one or more of the transducers  181   a - h  may be operated to at least temporarily reduce its transmit power for another of the tests. The test results for each of the tests may then be analyzed to determine which of the transmit profiles yields the best results. The most preferred transmit profile may then be selected for use with vehicles of the same or similar type. Further, the vehicle data  130  may be updated to reflect this decision such that when a vehicle identifier identifying a vehicle of the foregoing type is received, the preferred transmit profile is used to test the vehicle. Thus, the vehicle data  130  indicates not only the appropriate threshold profile to use for each vehicle, the vehicle data  130  also indicates the appropriate transmit profile to use for each vehicle.  
      The vehicle data  130  may correlate vehicle identifiers with the appropriate transmit profile information using the same or similar techniques as described above for correlating the appropriate threshold profiles with the vehicle identifiers. For example, the data  130  may store a list of VINs, and the data  130  may correlate each VIN with the respective transmit profile to be used to test the vehicle identified by the VIN. Alternatively, the data  130  may correlate different model identifiers with different transmit profiles, and the test manager  50  may extract the model identifier from a VIN to select the appropriate transmit profile. Various other techniques for selecting the appropriate transmit profile are also possible.  
      It should be noted, however, that the information indicating the appropriate transmit profile may be stored in other locations in other embodiments. For example, such information may be stored in the transmitter  33  such that communication with the test manager  50  is unnecessary to determine the appropriate transmit profile to be used for a particular vehicle  59 . Also, it is possible to use the same transmit profile for each vehicle such that it is unnecessary to determine whether the transmit profile for the transmitter  33  is to be changed from vehicle-to-vehicle as the transmitter  33  is re-used for different vehicles.  
      Various embodiments of the present disclosure have generally been described above as testing a passenger compartment  36  for abnormal leaks. Note that a vehicle may have more than one compartment to be tested. For example, a car may have a trunk separate from the passenger compartment, and it may be desirable to test the trunk for abnormal leaks in addition to testing the passenger compartment of the car. In such an example, transmitters  33  may be placed in both the passenger compartment and the trunk, and the testing described herein can then be performed to test both compartments. Alternatively, some vehicles have rear seats that, when placed into a folded position, create a passageway between the passenger compartment and trunk. In such a configuration, ultrasonic energy from a single transmitter  33  may flow within both the passenger compartment and the trunk allowing both compartments to be tested via the same transmitter  33 .  
      To better illustrate several of the foregoing concepts, an exemplary methodology for testing a vehicle  59  will be described hereafter.  
      For the purposes of illustration, assume that the vehicle data  130  defines the tables shown in  FIGS. 16 and 18 . Assume that the table of  FIG. 16 , referred to hereafter as the “first SUV profile,” is tailored for a first model of an SUV and the table of  FIG. 18 , referred to hereafter as the “second SUV profile,” is tailored for a second model of an SUV. Further assume that the vehicle  59  being tested is an SUV of the first model, which is similar to the SUV shown by  FIG. 15 , and assume that an abnormal leak exists only within region  141   d . Also assume that it has been determined that the preferred transmit profile, referred to hereafter as the “chirp profile,” for SUVs of the first model is for the transducers  181   a - h of transmitter  33  to sequentially emit ultrasonic energy such that only one transducer  181   a - h is emitting ultrasonic energy at any given instant in time. However, it has been determined that the preferred transmit profile, referred to hereafter as the “constant profile,” for SUVs of the second model is for all of the transducers  181   a - h to simultaneously and continuously emit ultrasonic energy at a constant transmit power.  
      In the current example, it will be further assumed that the vehicle identifier used to identify the vehicle  59  is its VIN, which uniquely identifies the vehicle  59  from all other vehicles. Moreover, the vehicle data  130  correlates the VIN with the first SUV profile depicted in  FIG. 16 , since this profile is the preferred threshold profile to be used to test the vehicle  59 . Thus, by analyzing the vehicle data  130 , the test manager  50  is able to select the first SUV profile for the vehicle  59  based on the VIN, as will be described in more detail hereafter. The vehicle data  130  also correlates the VIN with the chirp profile since this profile is the preferred transmit profile to be used to test the vehicle  59 . Thus, by analyzing the vehicle data  130 , the test manager  50  is able to select the chirp profile for the vehicle  59  based on the VIN, as will be described in more detail hereafter. Note that the vehicle data  130  may similarly correlate other VINs with threshold and transmit profiles defined by the data  130  so that the test manager  50  can similarly select the appropriate threshold and transmit profiles for other vehicles that may be tested by the system  30 .  
      Initially, the transmitter  33  is calibrated and placed within the passenger compartment  36  of the vehicle  59 , as shown by blocks  223  and  225  of  FIG. 22 . Exemplary techniques for calibrating transmitters and sensors are described in U.S. Provisional Application No. 60/730,429, entitled “Sensor Calibrating System and Method,” and filed on Oct. 26, 2005, which is incorporated herein by reference. As indicated by block  236  of  FIG. 22 , the transmit manager  185  of the transmitter  33  establishes a communication link with the test manager  50 . In the instant example, this is done by transmitting, via the communication interface  199  of  FIG. 21 , a message at a frequency (e.g., in the RF range) to enable the message to be received by the communication interface  83  of  FIG. 6 . The message includes a transmitter identifier, which identifies the communication interface  199  used by the transmitter  33  so that the test manager  50 , by including the transmitter identifier in messages destined for the transmitter  33 , enables the communication interface  199  to receive such messages. Upon receiving the message from the transmitter  33 , the test manager  50 , via communication interfaces  83  and  199 , transmits a reply message that includes the foregoing transmitter identifier, which enables the communication interface  199  to receive the reply message. The message also includes an identifier that identifies the communication interface  83  ( FIG. 6 ) so that the transmit manager  185 , by including this identifier in messages destined for the test manager  50 , enables the communication interface  83  to receive such messages. Thereafter, the transmit manager  185  may include, in each message transmitted to the test manager  50 , the identifier of communication interface  83 , and the test manager  50  may include, in each message transmitted to the transmit manager  185 , the identifier of communication interface  199 , thereby enabling successful communication between the test manager  50  and the transmit manager  185 .  
      After the communication link between the test manager  50  and the transmit manager  185  has been established, the transmitter  33  is put to sleep, as indicated by block  238 . This can be accomplished in response to a command from the test manager  50 . Alternatively, the transmit manager  185  can be configured to put the transmitter  33  into a sleep state without such a command from the test manager  50 .  
      As indicated by block  242  of  FIG. 22 , a vehicle identifier (i.e., the vehicle&#39;s VIN in the current example) identifying the vehicle  59  or the type of vehicle  59  is received by the test manager  50 . For example, the VIN may be attached to the vehicle  59  as is commonly done in current automotive assembly lines, and the optical scanner  88  ( FIG. 6 ) may be used to scan the VIN into memory  61 . Alternatively, the vehicle identifier may be entered into the system  63  via user input device  77  or otherwise.  
      Based on the VIN, the test manager  50  selects the appropriate threshold profile and transmit profile to be used to test the vehicle  59 , as indicated by block  244 . In the instant example, the vehicle data  130  correlates the vehicle&#39;s model identifier with the first SUV profile and the chirp profile. The test manager  50  extracts the vehicle&#39;s model identifier from the vehicle&#39;s VIN and consults the vehicle data  130 . Based on the vehicle data  130  and the model identifier, the test manager  50  selects the first SUV profile and the chirp profile for the threshold profile and the transmit profile, respectively, for the vehicle  59 .  
      At some point, the vehicle  59  moves toward the structure  52 , such as, for example, by the tracks  132  ( FIG. 2 ) moving the vehicle  59  toward and through the structure  52 . As the vehicle  59  passes through the structure  52 , the system  30  tests the vehicle  59  for abnormal leaks, as indicated by block  252  of  FIG. 22 .  
      In this regard, as the vehicle  59  is approaching the structure  52 , the test manager  50  monitors data from the object sensor  137  ( FIG. 3 ), which is in communication with the I/O interface  87  of  FIG. 6 . Once the vehicle  59  reaches the reference line  142  ( FIG. 3 ) and interrupts the optical signal being transmitted by the transmitter  141  to the sensor  137 , the sensor  137  reports this event to the test manager  50 . In response, as indicated by blocks  263  and  266  of  FIG. 23 , the test manager  50  begins tracking how far the leading edge  238  of vehicle  59  has moved from this line  142  based on data from the distance sensor  139  ( FIG. 2 ), which is in communication with the I/O interface  87  of  FIG. 6 .  
      Also, as indicated by block  269 , the test manager  50  wakes the transmitter  33  by transmitting a wake command to the transmit manager  185 . In response to this command, the transmit manager  185  powers up the components that are to be used during testing. For example, the transmit manager  185  activates the transducers  181   a - h that are to be used in testing. In the instant example, the transducers  181   a - h are to be operated in the chirp profile. In this regard, in addition to the wake command, the test manager  50  transmits, to the transmit manager  185 , data indicative of the transmit profile selected in block  244  of  FIG. 22  (i.e., the chirp profile in the instant example) so that the transmit manager  185  may control the operation of the transducers  181   a - h according to the selected transmit profile during testing. Thus, upon awakening the transmitter  33 , the transmit manager  185  controls the transducers  181   a - h  such that these transducers  181   a - h emit ultrasonic energy according to the chirp profile. Therefore, in the instant example, the transducers  181   a - h successively emit ultrasonic energy one after the other such that only one of the transducers  181   a - h  is emitting ultrasonic energy at any given instant in time. In other examples, the transducers  181   a - h may be controlled based on other transmit profiles.  
      In the instant example, assume that the test manager  50  is configured to take a sample every 12 inches or one foot along the length of the vehicle  59  starting with the leading edge  138  of the vehicle  59 . In such an example, the test manager  50  initializes a variable, x, to a value of zero, as indicated by block  272  of  FIG. 23 . In this regard, as indicated above with reference to  FIG. 3 , the value a represents the distance that the leading edge  138  of the vehicle  59  has progressed past the reference line  142 , and the value b represents the distance from the reference line  142  to the reference line  145  along which the sensors  45   a - p  are aligned. As indicated by block  275  of  FIG. 23 , the test manager  50  waits until the value of x is greater than or equal to the value of (a-b) indicating that the leading edge  138  of the vehicle  59  has arrived at the reference line  145 .  
      Note that while the vehicle  59  is passing through the structure  52 , the transmitter  33  is emitting ultrasonic energy according to the selected transmit profile. Further, the ultrasonic sensors  45   a - p  are detecting ultrasonic energy and providing values, referred to herein as “sample values,” indicative of the measured energy to the test manager  50 . Further, as indicated by block  277 , the test manager  50  determines whether x is greater than the total vehicle length. Until the vehicle  59  has completely passed reference line  145  ( FIG. 3 ), x should be less than the total vehicle length. The total vehicle length compared in block  277  may be indicated by the vehicle data  130  and correlated with the vehicle identifier of the vehicle  59  so that the test manager  50  can automatically access this value during testing.  
      Upon a “yes” determination block  275 , the test manager  50  takes the first sample, as indicated by block  278 , by retaining and storing, in memory  61  ( FIG. 6 ) as sample data  146 , the current sample value from each of the sensors  45   a - p . Note that the position of the vehicle  59  relative to the structure  52  is depicted by  FIG. 10  at the time of this first sample. As indicated by block  281 , the test manager  50  compares each sample value of this first sample to the associated threshold of the first SUV profile selected in block  244  ( FIG. 22 ). For example,  FIG. 16  indicates that the threshold associated with sensor  45   a  is 10.0. Thus, the test manager  50  compares this threshold with the sample value from sensor  45   a  for the first sample and detects a leak only if this sample value exceeds such threshold. The test manager  50  does the same for the other sample values of the first sample by comparing each sample value to the threshold of the first SUV profile that is associated with the respective sensor  45   a - p  from which the sample value was generated.  
      As indicated by block  284 , the test manager  50  determines whether any leaks have been detected for the current sample (i.e., the first sample in the instant example). If any leaks are detected via performance of block  281  for the current sample, then the test manager  50  indicates that a leak has been detected, as shown by block  287 . However, in the instant example, no leaks should be detected for the current sample. Thus, a “no” determination should be made in block  284 , and the test manager  50  then increases x by twelve (assuming that a and b are expressed in inches), as indicated by block  291 , so that the next sample will be taken twelve inches along the length of the vehicle  59  from the current sample.  
      After the first sample, the test manager  50  again makes a “yes” determination in block  275  once the leading edge  138  of the vehicle  59  has progressed about twelve inches past reference line  145  ( FIG. 3 ). At this point, the test manager  50  takes the second sample, as indicated by block  278 , by retaining and storing, in memory  61  as sample data  146 , the current sample value from each of the sensors  45   a - p . Note that the position of the vehicle  59  relative to the structure  52  is depicted by  FIG. 11  at the time of this second sample. As indicated by block  281 , the test manager  50  compares each sample value of this second sample to the associated threshold of the first SUV profile selected in block  244  ( FIG. 22 ). For example,  FIG. 16  indicates that the threshold associated with sensor  45   a  is    10 . 0   . Thus, the test manager  50  compares this threshold with the sample value from sensor  45   a  for the second sample and detects a leak only if this sample value exceeds such threshold. The test manager  50  does the same for the other sample values of the second sample by comparing each sample value to the threshold of the first SUV profile that is associated with the respective sensor  45   a - p  from which the sample value was generated.  
      As indicated by block  284 , the test manager  50  determines whether any leaks have been detected for the current sample (i.e., the second sample in the instant example). If any leaks are detected via performance of block  281  for the current sample, then the test manager  50  indicates that a leak has been detected, as shown by block  287 . However, in the instant example, no leaks should be detected for the current sample. Thus, a “no” determination should be made in block  284 , and the test manager  50  then increases x by twelve, as indicated by block  291 , so that the next sample will be taken twelve inches along the length of the vehicle  59  from the current sample.  
      Moreover, blocks  275 ,  277 ,  278 ,  281 ,  284 , and  291 , as well as block  287 , if appropriate, are repeated for each sample as the vehicle  59  passes through the structure  52 . Note that on the 9th sample, the sample value from sensor  45   d  should exceed the associated threshold compared to this sample value in block  281  since the corresponding region  141   d  has an abnormal leak in the instant example. Thus, the test manager  50 , in block  287 , indicates that a leak has been detected based on the data from this sensor  45   d.    
      For example, the test manager  287  may display a message, via user output device  79  ( FIG. 6 ), identifying the sensor  45   d . Alternatively, the test manager  50  may display information indicative of the region corresponding to the sensor  45   d  that detected the abnormally high amount of ultrasonic energy. As an example, the test manager  50  may display a graphical image similar to  FIG. 15 . The region  141   d  corresponding to sensor  45   d  may be highlighted indicating that this region  141   d  corresponds to a sensor  45   d  that detected an abnormally high amount of ultrasonic energy. Thus, a user may know to examine the vehicle  59  within or close to the highlighted region  141   d  for a possible leak.  
      In addition, the test manager  50  may provide one or more visual or audio alarms upon the detection of a leak so that workers within the vicinity of the structure  52  will be alerted to the leak. As an example,  FIG. 2  depicts a pair of multi-colored lights  322  that emit a color of light based on whether an abnormal leak has been detected. For example, in the absence of a detected leak, the lights  322  may exhibit a particular color, such as green, or may be turned off (i.e., emit no light). Upon the detection of a leak, the test manager  50  may be configured to cause the lights  322  to emit another color of light, such as red, to indicate that a leak has been detected.  FIG. 2  depicts another multi-colored light  325  that may be similarly controlled by the test manager  50  to indicate whether a leak has been detected. Also, the system  30  may comprise one or more speakers (not specifically shown), and the test manager  50  may communicate an audible alarm or message via such speakers in response to a detection of a leak.  
      Once the vehicle  59  has moved completely past the reference line  145 , the value of x should exceed the total length (in inches) of the vehicle  59 . Once this occurs, the test manager  50  makes a “yes” determination in block  277  and then puts the transmitter  33  to sleep, as indicated by block  333 . In this regard, the test manager  50  may transmit, to the transmit manager  145  of the transmitter  33 , a command that causes the transmit manager  185  to power down various components, such as transducers  181   a - h . Thus, the transducers  181   a - h stop emitting ultrasonic energy thereby conserving the transmitter&#39;s power supply  198 .  
      After performing the testing process depicted by  FIG. 23 , the test manager  50 , if desired, may report results of the testing process to a user, as indicated by block  338  of  FIG. 22 . For example, the test manager  50  may display, via user output device  79  ( FIG. 6 ), the sample values taken by the test manager  50  during the test. Alternatively, these sample values may be stored for future use or analyzed by a data analyzer (not specifically shown). For example, a data analyzer or a user may analyze the sample values in an attempt to precisely identify the locations of detected leaks.  
      Note that, if the ultrasonic transmitter  33  is not operating properly, then it is possible for a vehicle to falsely pass the test performed by the system  30 . For example, if the ultrasonic transmitter  33  fails to sufficiently emit ultrasonic energy during a test, then the sensors  45   a - p  may not detect sufficient ultrasonic energy to identify an abnormal leak within the vehicle being tested. This issue can be particularly problematic when the system  30  is implemented on an assembly line. In this regard, when the transmitter  33  fails, such as when batteries within the transmitter  33  run down, many vehicles may be tested by the system  30  before the failure in the transmitter  33  is discovered. Re-testing vehicles that have already moved off of the assembly line can be problematic and burdensome. Thus, the system  30  is preferably configured to automatically detect certain failures of the transmitter  33  and to provide a warning when such a failure is detected. Based on this warning, corrective action can be taken to mitigate the effects of the transmitter failure. As an example, the transmitter  33  can be quickly replaced with an operable transmitter, or the problem causing the transmitter failure can be diagnosed and corrected.  
      In one embodiment, the transmitter  33  comprises a transmit monitor  352  ( FIG. 21 ) that monitors the voltage or current provided by the power supply  198 . In one embodiment, the transmit monitor  352  is implemented in hardware, but it is possible for at least portions of the transmit monitor  352  to implemented in software in other embodiments.  
      If the monitored voltage or current provided by the power supply  198  falls below a predefined threshold, then the transmit monitor  352  notifies the transmit manager  185 . In response, the transmit manager  185  provides a warning about the imminent failure of the power supply  198 . For example, the transmit manager  185  may communicate an audible or visual alarm indicating imminent failure of the power supply. As a mere example, the user output device  195  may comprise a light source (not specifically shown), such as a light emitting diode (LED), that when lit indicates imminent failure of the power supply  186 . The test manager  185  may illuminate such a light source in response to the aforementioned notification from the transmit monitor  352 .  
      In addition, the transmit manager  185  may communicate a message to the test manager  50  via communication interfaces  199  and  83  ( FIG. 6 ). The transmit manager  185  may then report the detection of the imminent transmitter failure to a user via user output device  79 . As an example, the transmit manager  185  may illuminate one of the lights  322  or  325  in a particular manner or color to indicate detection of a possible transmitter failure. The transmit manager  185  may also provide an audible alarm to indicate the possible transmitter failure. Moreover, various other techniques for alerting users to the failure or imminent failure of the transmitter  33  are possible.  
      It should be noted that the transmit monitor  352  may be used to detect other types of transmitter failures. For example, the transmit monitor  352  may monitor the operation of the transducers  181   a - h to detect when any of the transducers  181   a - h fails. In this regard, for each transducer  181   a - h , the transmit monitor  352  monitors the impedance of the transducer  181   a - h and determines when this impedance significantly changes thereby indicating possible failure of the transducer  181   a - h . Note that the impedance may be monitored by measuring the voltage drop across the transducer  181   a - h assuming that the current provided to the transducer  181   a - h is constant. Thus, the transmit monitor  352  may be configured to determine the voltage drop (i.e., the difference between the input voltage and the output voltage) across each transducer  181   a - h  and compare each voltage drop to a specified threshold. If the voltage drop across any transducer  181   a - h falls below the specified threshold, then the transmit monitor  352  detects a possible failure for that transducer  181   a - h  and notifies the transmit manager  185 . The transmit manager  185  then provides a warning to a user. Note that the same or similar techniques described above for warning about a possible failure or imminent failure of the power supply  198  may be used to warn of a possible failure or imminent failure of a transducer  181   a - h . Other types of failures may be similarly detected and reported by the system  30 .  
      Moreover, by detecting abnormal leaks and identifying locations of the detected leaks as described above, the system  30  provides an effective tool for helping users to identify and remedy leak-related problems in vehicles and/or other products having compartments. Note that U.S. Patent Application (attorney docket no. 731701-1050), entitled “System and Method for Detecting Leaks in Sealed Compartments,” and filed on Oct. 25, 2006, which is incorporated herein by reference, describes various exemplary techniques that may be used to detect leaks in compartments.  
      The present disclosure has been described as employing ultrasonic signals to detect abnormal leaks in sealed compartments. However, using signals of other frequency ranges is also possible. In addition, the sensors  45   a - p  have been described herein as receiving energy emitted by a transmitter  33 . However, it is possible for transmitters to be located on the outside of the vehicle  59  being tested and for one or more receivers to be located in the vehicle  59 . For example, each of the sensors  45   a - p  described herein could be replaced by a transmitter transmitting ultrasonic energy in a different frequency range. For each sample, one or more receivers within the vehicle  59  could detect the amount of ultrasonic energy within the frequency ranges used by the transmitters. If an abnormally high amount of ultrasonic energy within a frequency range transmitted by a particular transmitter is detected within the vehicle  59 , then it could be assumed that an abnormal leak exists in the region corresponding to the particular transmitter. In such an example, the overall testing methodology could be similar to those described above except that ultrasonic energy is directed at the vehicle  59  by devices  45   a - p  rather than being received by the devices  45   a - p . Various other modifications to the system  30  would be apparent to one of ordinary skill in the art upon reading this disclosure.  
       FIG. 24  depicts an exemplary computer system  2400  that can be employed in a leak detection system  30  ( FIG. 1 ). The computer system  2400  comprises a test manager  2450 , and substantially similar to the computer system  63  ( FIG. 6 ), the test manager  2450 , along with its associated methodology, is implemented in software and stored within memory  2461  of the computer system  2400 . In other embodiments, the test manager  2450  can be implemented in hardware or a combination of hardware and software. For brevity, each of the elements of the computer system  2400  operates substantially similar to those elements depicted in  FIG. 6  having like reference numerals.  
      Additionally, the memory  2461  further comprises interface data  2405 , and the sample data  146  comprises a plurality of sample data sets  146   a - 146   d , which are described further herein.  
      Similar to test manager  50  ( FIG. 6 ), test manager  2450  determines whether the compartment  36  ( FIG. 3 ) has any abnormal leaks and identifies a location of each abnormal leak detected by the leak detection system  30  based upon the ultrasonic energy detected via the sensors  45   a - p  ( FIG. 2 ). As further described herein, the test manager  2450  compares values indicative of the ultrasonic energy detected by each of the sensors  45   a - p  with threshold values of the vehicle&#39;s threshold profile.  
      In one embodiment of the leak detection system  30 , the test manager  2450  is configured to display, via the user output device  79 , a graphical user interface (GUI)  2500 , such as is depicted in  FIG. 25 , defined by the interface data  2405 . The GUI  2500  is described in more detail with reference to  FIG. 25 .  
      In addition, the test manager  2450  is further configured to store a plurality of sample data sets  146   a - 146   d . In this regard, each sample data set  146   a - 146   d  represents the sample values from each of the sensors  45   a - p  ( FIG. 2 ) stored by the test manager  2450  during the testing process for a single vehicle. Thus,  FIG. 24  depicts memory  2461  as storing sample data sets  146   a - 146   d  for four vehicles. Note that storing sample data sets  146   a - 146   d  for four vehicles is for exemplary purposes, and other numbers of sample data sets may be stored in other embodiments of the computer system  2400 .  
      With regard to  FIG. 25 , GUI  2500  comprises exemplary vehicle representation windows  2501 - 2504  illustrating various vehicle images  2525 - 2528  that may be representative of a vehicle that is currently under test by the leak detection system  30  ( FIG. 1 ). Note that images  2525  and  2528  depict exemplary opposing side views of the vehicle under test, and images  2526  and  2527  each depict a top view of the vehicle under test. However, different views of the vehicle exhibited in the windows  2501 - 2504  may be used in other embodiments, and the views illustrated are for exemplary purposes only.  
      Note that the representation windows  2501 - 2504  may display any type of illustration that depicts the various views of the vehicle under test. In this regard, the representations may be digital images of the actual vehicle or line drawings of the vehicle, for example. Further note that the image does not necessarily correspond to the model of the vehicle currently under test. In other embodiments, different GUIs are correlated with the VIN or model number/type of the vehicle being tested.  
      In one exemplary embodiment, the interface data  2405  defines a plurality of GUIs and each GUI is associated with a different vehicle model. Further, the vehicle images defined by each GUI appear similar to the associated vehicle model. When the results of a test for a vehicle of a particular type are to be displayed, the GUI associated with the model type of the tested vehicle is used to display the test results. As described above, the model type can be determined from the vehicle&#39;s VIN. Thus, when the test results of a vehicle are displayed, the displayed vehicle images appear similar to the tested vehicle. As an example, vehicle images  2525 - 2528  in windows  2501 - 2504  may be used when the results are being displayed for an SUV. A different set of images may be displayed when the results of tests performed for a different type of vehicle are displayed.  
      Furthermore, a text box  2509  may display a vehicle identification number (VIN) associated with the vehicle that is currently under test and illustrated via the representation windows  2501 - 2504 . In addition, a text box  2508  may display a VIN associated with a vehicle that is going to be tested via the leak detection system  30  after the vehicle associated with the VIN displayed in text box  2509 .  
      The GUI  2500  further comprises a plurality of graphical tables  2505 - 2508  having segmented regions  2512  for indicating an ultrasonic sample value from a respective one of the sensors  45   a - p . In this regard, each graphical table  2505 - 2508  comprises a plurality of rows  2560 - 2575  corresponding to a plurality of respective sequential samples performed by the sensors  45   a - p  ( FIG. 2 ) as a vehicle  59  ( FIG. 2 ) travels through the structure  52  ( FIG. 2 ). Furthermore, each graphical table  2505 - 2508  comprises a plurality of columns a-p corresponding to the plurality of sensors  45   a - p . Note that each region  2512  is associated with at least one threshold value as depicted in the threshold profile in  FIG. 16 . In addition, each of the regions  2512  corresponds to a physical location of the vehicle. Each region corresponds to the physical location that the region appears to cover in the vehicle image. For example, region  2514  appears to cover a portion of the depicted vehicle close to the bottom, middle of the front, driver-side window, and region  2514 , therefore, corresponds to such region of the vehicle. In addition, each region  2412  includes an indicator, such as a value, indicating the level of ultrasonic energy measured by the corresponding sensor  45   a - p.    
      For example, region  2514  in window  2501  exhibits a “46,” which is a value indicative of ultrasonic energy detected by sensor  45   d  ( FIG. 2 ) as the portion of the vehicle  59  that appears to be covered by the region  2514  passes through the structure  52 . The test manager  2450  ( FIG. 24 ) compares such a value, e.g., “46,” with a value in the threshold profile, e.g., the profile depicted in  FIG. 16 , corresponding to the make and/or model of the vehicle  59  being tested.  
      Therefore, while a vehicle  59  is under test, as described herein, the test manager  2450  determines whether the energy detected by one of the sensors  45   a - p  ( FIG. 2 ) exceeds an associated threshold defined by a threshold profile selected for the particular vehicle under test. Further, in one embodiment of the GUI  2500 , the test manager  2450  may display an indicator (not shown) within one of the regions  2512  indicating whether the corresponding portion of the vehicle under test passed the testing preformed by the leak detection system  30 . In this regard, if the vehicle likely contains an abnormal leak (e.g., an associated threshold defined by the threshold profile is exceeded indicating that a leak may exist in or close to such portion), then the test manager  2450  may highlight that particular region  2512  corresponding with the leak. Thus, by simply looking at the display, a user can readily discern which vehicle regions likely contain or are close to leaks.  
      For example, in window  2501 , the vehicle under test may have a leak on a portion of the vehicle corresponding to region  2514  (e.g., close to the bottom, middle of the front, driver-side window). Thus, the test manager  2450  may highlight entry  2514  to indicate to a user (not shown) viewing the windows  2501 - 2504  that there may be a leak associated with that portion of the vehicle under test corresponding to the highlighted entry  2514 . In addition, the test manager  2450  may highlight other entries  2515  and  2516  surrounding the entry  2514  that similarly indicate elevated ultrasonic energy emissions relative to the threshold profile selected for the vehicle under test.  
      The test manager  2450  may indicate increased ultrasonic energy above the profile thresholds by highlighting regions  2512  in the tables  2505 - 2508 , as described herein. In this regard, the test manager  2450  may fill regions  2512  with a particular color, e.g., red, if the energy detected exceeds a particular first threshold. Furthermore, the test manager  2450  may fill other entries  2512  with a different color, e.g., green, to indicate a particular second threshold or another color; e.g., yellow to indicate a third threshold.  
      For example, in various embodiments described above, the threshold profile is described as associating a threshold for each sample value. If the sample value exceeds the associated threshold, then a detection of an abnormal leak is made. However, in other embodiments, each sample value may be associated with a plurality of thresholds, and the output provided by the system  30  may indicate whether each of the thresholds is exceeded. As an example, assume that sensor  45   d  corresponds to region  2514  for a particular sample. The sample value from sensor  45   d  could be compared to two associated thresholds. If the value exceeds only the lower threshold, then the test manager  2450  may highlight region  2514  of window  2501  by coloring this region  2514  yellow. If both thresholds are exceeded, then the test manager  2450  may highlight region  2514  of window  2501  by coloring this region red. If neither of the thresholds are exceeded, then the test manager  2450  may refrain from highlighting the region  2514  or may highlight the region a different color, such as green. Thus, the region  2514  is color coded to indicate an extent of ultrasonic energy detection for the corresponding physical region of the vehicle being tested. In addition to or in lieu of the color highlighting, a value (e.g., the corresponding sample value or the difference between the corresponding sample value and its associated threshold) indicative of the extent of ultrasonic energy detected for the corresponding physical region may be included in the region  2514 . Various other techniques for indicating the extent of ultrasonic energy detection for each sample are possible in other embodiments.  
      As described herein, as a plurality of vehicles are tested, for example on a manufacturing line, the test manager  2450  defines and stores sample data  146  ( FIG. 6 ) associated with each vehicle that is tested by the leak detection system  30 .  FIG. 26  depicts an exemplary system  2600  comprising the leak detection system  30  ( FIG. 1 ) and a data storage and access system  2602 .  
      In such a system  2600 , the sample data  146  comprises the sample data sets  146   a - 146   d , as described with reference to  FIG. 24 . Each sample data set  146   a - 146   d  comprises data resulting from a leak test and corresponding to a particular vehicle that has been tested by the leak detection system  30 . Each sample data set  146   a - 146   d  comprises, in particular, data (e.g., sample values and/or differences between sample values and associated thresholds of the selected threshold profile) indicative of the ultrasonic energy detected by the leak detection system  30  corresponding to physical locations on the corresponding vehicle that has been tested.  
      For example, each sample data set  146   a - 146   d  may include the vehicle identifier of the corresponding vehicle and the sample values measured by the sensors  45   a - p  ( FIG. 2 ) for each of the samples during the test of the vehicle. In another embodiment, each sample data set  146   a - 146   d  may include the vehicle identifier and the difference between each sample value and the associated threshold used to determine whether the sample value is excessive. Moreover, any sample data set  146   a - 146   d  may be analyzed to assess the sealing characteristics of the identified vehicle and, in particular, to estimate the approximate amount of leakage for different portions of the vehicle.  
      The data storage and access system  2602  further comprises interface logic  2603  and a database  2620 , each resident in memory  2604 . Note that the interface logic  2603  may be implemented in software, hardware, or a combination thereof. The test manager  2450  transmits sample data sets  146   a - 146   d  periodically to the data storage and access system  2602 . The test manager  2450  may transmit the data sets  146   a - 146   d  over a network (not shown in  FIG. 26 ). In other embodiments, the data sets  146   a - 146   d  may be uploaded to the data storage and access device  2602  via other techniques. Upon receipt of the data sets  146   a - 146   d , the interface logic  2603  stores received sample data sets  146   a - 146   d  in the database  2620 . In this regard, the database  2620  comprises a plurality of VINs corresponding to sample data sets  146   a - 146   d  that may be searched via the interface logic  2603 . In other embodiments, the data sets  146   a - 146   d  may be stored in other types of memory.  
       FIG. 27  depicts an exemplary system  2700  comprising a plurality of end-user sites  2701 - 2702  and a plurality of manufacturing sites  2703 - 2704 . The sites  2701 - 2704  communicate via the network  2712 . In addition, the system  2700  comprises a computing device  2705  that also communicates via the network  2712 . The network  2712  can comprise the public switched telephone network (PSTN), the Internet, or some other type of network.  
      The computing device  2705  comprises the data storage and access system  2602 , such as is depicted in  FIG. 26 . Thus, when vehicles (not shown) are manufactured at the manufacturing sites  2703 - 2704 , sample data sets  146   a - 146   d  ( FIG. 26 ) corresponding to each vehicle manufactured are stored at the manufacturing sites  2703 - 2704 . In addition, such sample data sets  146   a - 146   d  corresponding to each vehicle manufactured are stored on the data storage and access system  2602 . In such an example, the test manager  2450  may store the sample data sets  146   a - 146   d  locally and/or transmit the sample data sets  146   a - 146   d  to the computing device  2705  via network  2712  or otherwise.  
      Note that two manufacturing sites  2703 - 2704  are shown for exemplary purposes. Other numbers of manufacturing sites in other embodiments are possible. Furthermore, each manufacturing site  2703 - 2704  is preferably communicatively coupled to the network  2712  so that sample data sets  146   a - 146   d  may be transferred to the data storage and access device  2602 . However, transferring the data sets  146   a - 146   d  to the device  2602  via other techniques is also possible.  
      The computing device  2705  may be, for example, a web server. Such device  2705  may make the contents of the data storage and access system  2602  available via a web site accessible by a web identifier, e.g., an hypertext transfer protocol (HTTP) identifier. As another example, the computing device  2705  may be a secure server, and the data storage and access system  2602  may only provide contents of the database  2620  ( FIG. 26 ) in response to secure transaction requests.  
      As an example, the end-user sites  2701 - 2702  may each comprise a data access system  2715 . For example, the data access system  2715  may comprise a personal computer (PC) located at the end-user site  2601 - 2602 . The end-user site  2601 - 2602  may be, for example, an automobile dealership.  
      In such an example, a customer (not shown) of the automobile dealership may bring a previously purchased vehicle to the dealership. The customer may complain of a leakage problem, e.g., there is wind noise in the compartment of the vehicle or there is a water leak in the compartment of the vehicle.  
      A user of the data access system  2715  may then retrieve data corresponding to the previously purchased vehicle from the data storage and access system  2602 .  FIG. 28  depicts an exemplary embodiment of the data access system  2715 . The exemplary system  2715  depicted by  FIG. 28  comprises at least one conventional processing element  2752 , such as a digital signal processor (DSP) or a central processing unit (CPU), that communicates to and drives the other elements within the system  2715  via a local interface  2759 , which can include one or more buses. Furthermore, a user input device  2763 , for example, a keyboard or a mouse, can be used to input data from a user of the system  63 , and a user output device  2779 , for example, a printer or monitor, can be used to output data to the user. In addition, a network interface  2779  enables communication with the network  2712  ( FIG. 27 ).  
      The system  2715  also comprises memory  2788  having a web browser  2791  stored therein. Using the web browser  2791 , the user may log onto the data storage and access system  2602  through the interface logic  2603 . In such an example, the interface logic  2603  may comprise a gateway or other front-end processor that provides a secure interface for controlling access to the database  2620 .  
      In this regard, the user may transmit a username and password to the interface logic  2603 , for example. The user may then enter a unique identifier, e.g., a VIN, corresponding to the vehicle for which the user desires to retrieve information corresponding to the vehicle leak test previously performed at the manufacturing sites  2703 - 2704 . The interface logic  2603  may then search the database  2620  using the entered unique identifier, retrieve the sample data set  146   a - 146   d  corresponding to the entered unique identifier, and transmit the corresponding sample data set  146   a - 146   d  to the end-user site  2702 - 2703  for viewing by the user. Such data may be used by the user to pinpoint or at least narrow down the location possibilities associated with the leak about which the customer is complaining.  
       FIG. 29  depicts exemplary architecture and functionality of the system  2600  depicted in  FIG. 26 .  
      As indicated by block  2800 , the leak detection system  30  ( FIG. 1 ) tests a vehicle to determine whether the vehicle is exhibiting any abnormal leakage. The leak detection system  30  stores sample data sets  146   a - 146   d  ( FIG. 25 ) indicative of the results of the testing in block  2801 .  
      As indicated by block  2802 , the data storage and access system  2602  ( FIG. 26 ) receives a request from a user to retrieve a sample data set  146   a - 146   d  ( FIG. 26 ) corresponding to a particular VIN. Such data may be stored locally with reference to the leak detection system  30 , or the sample data set  146   a - 146   d  may be stored on a remote device, e.g., the computing device  2705  ( FIG. 26 ).  
      As indicated by block  2803 , the data storage and access system  2602  may retrieve the sample data set  146   a - 146   d  associated with the particular VIN number in response to the request. As indicated by block  2804 , the data storage and access system  2602  then transmits the retrieved sample data set  146   a - 146   d  to the requesting user.  
      The user may then generate a printed report embodying the retrieved sample data set  146   a - 146   d , including a report exhibiting a graphic substantially similar to the GUI  2500  as depicted in  FIG. 25 . In this regard, the user may use the generated report to identify the location on the previously purchased vehicle that may have a leak. Alternatively, the user may display a GUI similar to the GUI  2500  ( FIG. 25 ) to aid in the identification of the location of a leak on the recently purchased vehicle.