Abstract:
Sound detection techniques and sound discrimination techniques are used to analyze the real time sounds generated during the operation of cleaning heads operating within a vessel to determine if the cleaning heads are operating properly. During a typical cleaning operation pressurized cleaning solution is dispensed through a rotating nozzle assembly inside the vessel. As the nozzles rotate the spray moves about the interior of the vessel creating a unique sound pattern. By placing one or more pickups on the interior of the vessel the sound is captured and fed to an analyzing device for analysis. Key properties such as, but not limited to, sound pressure levels, amplitude variations, spectral content, and rotational information are extracted and analyzed against the reference parameters.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation-in-part of pending U.S. Application No. 10/039,835, filed Oct. 23, 2001, which is based upon Provisional Application Serial No. 60/242,555, filed on Oct. 23, 2000 and Provisional Application Serial No. 60/281,588, filed on Apr. 5, 2001, both of which are incorporated fully herein by reference. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to method and apparatus for monitoring and evaluating the operation of rotary element cleaning devices from the exterior of a vessel based upon sound analysis.  
         BACKGROUND OF THE INVENTION  
         [0003]    There are many machines that include a vessel having cleaning elements (e.g., rotary, reciprocating, stationary, etc.) contained within them for the purpose of cleaning items within the vessel, or even the vessel itself. Consider, for example, the common dishwasher. A dishwasher typically comprises a closed vessel with a rotating cleaning device located at the bottom of the vessel. When the dishwasher is operating, there is no way of seeing inside to determine if the cleaning elements are operating properly. Frequently, a fork or knife may fall through the dish rack and block the rotation of the rotating spray arm, which is part of the rotary cleaning element. The result of the blockage is a poor cleaning cycle which in turn results in unclean dishes. However, the first indication of this problem is at the end of the cleaning cycle when the dishwasher is opened to empty the contents, and at this point it is too late, as the time and resources associated with operation of the dishwasher have already been consumed.  
           [0004]    Current industry solutions for this problem include installation of a window in the vessel, which gives a visual accounting of the cleaning activity, or the use of an electronic pressure switch inside the vessel that senses the impact of the spray coming from the spray arm. Both have significant shortcomings.  
           [0005]    Most vessels do not have windows since they are very expensive to install and labor intensive to monitor. To install a window an opening must be cut through the vessel wall. The interior of the enclosure must then be illuminated so the observer may see through the window into the vessel. Even with the illumination, the observer may not be able to view the operation of the cleaning elements through the window due to cleaning solution collecting on the inner surface of the window. In the case of a rotary cleaning element, all the observer can tell is that the rotary element is (or is not) rotating and/or spraying liquid; it is very difficult, if not impossible, to make significant qualitative assessment of the operation of the rotary element. The problem is further complicated if two or more cleaning devices are operated simultaneously within the vessel. One may stop while the other(s) continues to operate. The observer may see the spray from the properly-operating device striking the window and be given the false impression that all of the devices are operating properly. Mistakenly the observer may believe that all is well.  
           [0006]    Installation of a pressure switch that generates a signal when impacted by the spray from the cleaning devices is a more reliable solution than the above-described window solution. The primary downfall to pressure switches involves environmental considerations which may degrade the switch and/or its performance, such as high temperatures, pressurization and caustic cleaning solutions. As in the case of the window, installing the pressure switch also requires a penetration through the vessel wall. The positioning of the switch is critical since to be reliable it must receive “hits” from the cleaning spray on a regular basis. The only location meeting this requirement may be a very small area relative to the spray device. A poorly placed sensor will likely yield unreliable indications.  
           [0007]    As noted above, both the window and the pressure switch solutions require penetrations to be made through the vessel wall. In addition to being expensive, in a great many instances it is not possible due to the intended usage, construction, or placement of the vessel within a facility.  
           [0008]    It is common in the food, beverage and drug industries to utilize large vessels for processing, storing and/or transporting product. For example, tanks are used in the production, storage and transporting of whisky, beer &amp; wine. These tanks range in size from several hundred gallons to tens of thousands of gallons. In order to produce an acceptable product for sale and/or to satisfy FDA regulations, these tanks must be hygienically cleaned between usages. Specialized cleaning equipment has been developed that can be inserted or in many cases sealed into the tanks to perform the cleaning process.  
           [0009]    There are many examples of such cleaning systems. For example, Toftejom, Inc. of Pasadena, Texas; Sellers Cleaning Systems of Piqua, Ohio; and Gamma Jet Cleaning Systems, Inc. of DeVault, Pa., all manufacture and sell such devices. These devices typically have one or more spray heads that have both horizontal and vertical rotational patterns.  
           [0010]    Examples of such cleaning devices can be found in U.S. Pat. No. 6,123,271 and U.S. Pat. No. 5,954,271.  
           [0011]    FIGS.  1 A- 1 C and  2  illustrate, respectively, a typical prior art spray head and a typical tank environment in which this prior art spray head is used. Referring to FIGS.  1 A- 1 C, an inlet pipe  100  has a rotational sleeve  102  on which a spray head  104  is attached. Spray head  104  has situated around its perimeter a plurality of discharge nozzles  106  (three are shown in FIGS.  1 A- 1 C). Spray head  104  rotates along axis A 2  around the inlet pipe  100 , and also rotates along axis Al, thereby resulting in a “three-dimensional” spray pattern.  
           [0012]    Referring now to FIG. 2, a tank  210  has an inlet pipe  200  inserted therein, with the inlet pipe  200  having, in this example, two spray heads  204 A and  204 B, each of which correspond to the spray head detailed in FIGS.  1 A- 1 C. In operation, the entire assembly (the inlet pipe  200  and the rotational spray heads  204 A and  204 B) is inserted into the tank  210  to be cleaned, and pressurized water is introduced into the inlet pipe  210 . In a well known manner (see, e.g., the above-referenced U.S. Pat. Nos. 6,123,271 and 5,954,271), the introduction of the pressurized water into inlet pipe  200  causes the rotational movement of the spray heads  204 A and  204 B along both axes A 1  and A 2  of FIGS.  1 A- 1 C, generating a spray pattern as illustrated generally by the solid arrows and dotted line arrows of FIG. 2. It is understood, of course, that the spray pattern illustrated in FIG. 2 is shown merely to illustrate the general idea of this prior art system and is not intended to shown the precise spray pattern of the spray heads.  
           [0013]    Cleaning devices of the type described above operate quite well and are used throughout industry for cleaning purposes. However, it is often difficult to determine if the cleaning heads are functioning properly since, like the dishwasher described above, the operation of the device occurs inside the sealed vessel and out of the view of the operator. To ensure that the products contained in the vessels are not contaminated due to a poor cleaning cycle caused by a cleaning device malfunction, the operation of the cleaning devices should be monitored on a regular basis. Since this is difficult to accomplish, the common practice is to (1) periodically test the cleaning equipment outside of the vessel and/or (2) test the final product for contaminants after the fact. Periodically testing the cleaning equipment outside of the vessel, of course, only assures that the device is working when it is being tested, and not during operation. Testing the final product for contaminants after the fact, on the other hand, runs the risk of producing a bad batch of product and that must therefore be disposed of. In many instances the contaminated product is considered hazardous waste and must be disposed of at great cost and/or difficulty. Accordingly, it would be desirable to have a cleaning head monitoring system that can, on a real time basis, and from the exterior of the vessel, accurately monitor the operation of the cleaning head during the cleaning operation.  
         SUMMARY OF THE INVENTION  
         [0014]    The present invention utilizes sound detection techniques and sound discrimination techniques to analyze the real time ongoing operational sounds generated during the operation of cleaning heads operating within a vessel to determine if the cleaning heads are operating properly. The term “sound,” as used herein, includes mechanical vibrations both within and outside the perception of human hearing.  
           [0015]    During a typical cleaning operation pressurized cleaning solution is dispensed through a nozzle assembly inside the vessel. In the case of a rotating spray head, as the nozzles rotate the spray moves about the interior of the vessel creating a unique sound pattern. By placing one or more pickups on the interior or exterior of the vessel the sound is captured and fed to an analyzing device for analysis. Key properties such as, but not limited to, sound pressure levels, amplitude variations, spectral content, and rotational information are extracted and analyzed against the reference parameters.  
           [0016]    In a preferred embodiment, “reference parameters” (also referred to as “sound signatures,” “reference sound values,” “reference frequency patterns”) derived from a properly functioning cleaning cycle are compared with equivalent parameters derived on an ongoing basis during subsequent cleaning cycles (referred to herein as “ongoing operational sound values,” “captured sound values,” “measured frequency patterns”). Based upon the comparison, it is determined whether or not the cleaning heads are functioning properly. In a preferred embodiment, filtering techniques are used to increase the accuracy of the comparison. 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0017]    FIGS.  1 A- 1 C illustrate a typical prior art spray head with which the present invention may be used;  
         [0018]    [0018]FIG. 2 illustrates a typical vessel configuration with which the present invention may be used;  
         [0019]    [0019]FIG. 3 illustrates an example of a dual cleaning head, dual sound sensor system in accordance with an embodiment of the present invention;  
         [0020]    [0020]FIG. 4 is a block diagram illustrating the basic functions performed by a signal processor of Figure;  
         [0021]    [0021]FIG. 5 is a detailed block diagram of an example of a 2-channel embodiment of the present invention;  
         [0022]    FIGS.  6 A- 6 D are amplitude-over-time graphs illustrating the development of RMS images from raw signal data in accordance with the present invention;  
         [0023]    [0023]FIG. 7 is an amplitude-over-time graph illustrating an enhanced image of the rotational information related to spray devices in accordance with the present invention; and  
         [0024]    [0024]FIG. 8 is an illustration depicting the various sound components received by the sound sensing elements of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0025]    The present invention will now be described in detail with reference to FIGS.  3 - 8 . FIGS. 3 and 4 illustrate an example in which two rotational cleaning heads and two sound sensing elements are utilized; it is understood, however, that more or less than two cleaning heads and/or sound sensing elements may be used and still fall within the scope of the claimed invention, and that the cleaning heads may include reciprocating, rotary, and/or stationary cleaning heads.  
         [0026]    Referring to FIG. 3, the present invention is described being utilized to monitor a cleaning system similar to that described in FIG. 2, specifically, a vessel  310  having inserted therein an inlet pipe  300  having attached thereto cleaning heads  304 A and  304 B. In accordance with the present invention, pickups  312 A and  312 B (e.g., microphones, transducers, or other spectral sensing elements) are pressed against and, preferably, temporarily or permanently affixed to, vessel  310 . Alternatively, pickups  312 A and  312 B can be mounted internally. Internally mounted pickups must be able to operate in the environment existing inside the vessel (e.g., liquid, chemicals, detergents, etc.). Pickups of this type are well known. The internal pickups can be hardwired through the wall of the vessel or can be configured to wirelessly transmit the data derived from their sensing elements to a receiver located outside the vessel. The area of the vessel immediately adjacent to each pickup is referred to herein as the “sensing area” of the pickup, i.e., the area of the vessel from which a pickup will sense sounds most strongly.  
         [0027]    Each pickup and the signal processing (discussed below) associated with the sounds sensed by each pickup represents a separate “channel”, i.e., a single-pickup system has one channel, a dual-pickup system has two channels, etc. Pickups  312 A and  312 B detect sounds occurring at their respective sensing areas and produce a sound signal corresponding to the sensed sounds in a well-known manner. The sound signals are input to a signal processor  316 , details of which are described below in connection with FIGS. 4 and 5. A display  346  (e.g., a monitor or other display device) is connected to signal processor  316  to display results of the signal processing, if desired. A PC  348  or other processing device is attached to signal processor  316  to provide for data input and data storage and control of other functions based on the signal processing results.  
         [0028]    [0028]FIG. 4 is a block diagram showing the basic functions performed by signal processor  316  to perform the analysis/validation method of the present invention. The method of the present invention can be performed using three basic blocks: an audio processing block  420 ; a signal enhancement block  422 ; and a sound analysis block  424 . The signals sensed by one or more pickups (collectively identified by item  412  in FIG. 4) are processed in the audio processing block  420 . If more than one pickup  412  is being used to sense the sound coming from inside the vessel, the signal enhancement block  422  is used to, for example, allow cancellation of certain sounds sensed from within the vessel. Finally, the sound analysis block  424  performs analysis on the received sounds to determine if the cleaning device is operating properly. Each of these blocks is discussed in more detail below in connection with FIG. 5.  
         [0029]    [0029]FIG. 5 is a detailed block diagram of an example of a two-channel embodiment of the present invention. The block diagram illustrated in FIG. 5 is given by way of example only; it is understood other embodiments are contemplated that provide a signal processing system that receives input sound signals relating to the operation of one or more operational elements of a machine, analyzes the sound signals, and provides output identifying problems with the operational elements.  
         [0030]    A signal conditioner  520 A preconditions the signals received from pickup  312 A. This preconditioning includes, but is not limited to, filtering out of unwanted noise components that are known to be irrelevant. For example, if the frequency of the sounds sensed by the pickups on a typical vessel centers around 1000 Hz., and if it is known that signal components above 1800 Hz. and below 200 Hz. are of little or no value, then signal conditioner  520 A can be configured to comprise a filter that passes only a band of frequencies between 200 Hz. and 1800 Hz. (referred to herein as the “pass band”). This serves to improve the signal to noise ratio of the signal being analyzed. Any known filtering method may be utilized, for example, a simple RC filter.  
         [0031]    An amplifier  522 A amplifies the received signals to a desired level in a known manner. The purpose of the amplification performed by amplifier  522 A is to set the signal level to the optimum level for the rest of the process performed by the system of the present invention. The sound signal is considered optimized when the peak signal into an analog-to-digital converter  524 A (discussed below) is slightly below its full dynamic range. An adjustment means  523 A (e.g., a potentiometer) allows adjustment of the gain of the amplifier so that it can provide the optimized signal; in a preferred embodiment the amplifier  522 A and adjustment means  523 A comprises a microprocessor configured in a known manner. The amplifier  522 A is automatically adjusted by having the microprocessor configured to evaluate the output signal of the analog-to-digital converter and adjust the output of amplifier  522 A to the optimized level.  
         [0032]    The output of the amplifier  522 A is fed to an analog-to-digital converter  524 A where it is converted to a digital signal. While it is understood that the present invention can be practiced without converting the analog signal to a digital signal, a digital signal can be more easily and accurately processed. The AID output is fed to FIFO buffer  562 A. A FIFO buffer enables the output of the amplifier  522 A to be sampled by A/D converter  524 A at “M” samples per second and processed in  528 A in frames (groups) of “N” samples per frame, where “M” and “N” are variables representing a predetermined number of samples, the exact number of which is discretionary to the user of the system. For example, using buffer  526 A, the output of the amplifier  522 A may be sampled and stored into buffer  528 A at a rate of  11  K samples/second and output to  528 A in frames of 1024 samples every 1024/11000 seconds.  
         [0033]    A processor  528 A RMS averages the samples contained in the frame (a well-known math process which can be performed using, for example, prior art RMS averaging methods), storing the results in RMS buffer  530 A as a single RMS value. Two tasks are accomplished by RMS averaging the samples in frames of “N” samples. First, the signal is low pass filtered (sample rate/frame size). Second, as additional frames are processed and stored in RMS buffer  530 A, a running low-frequency RMS image of the sound fluctuations (referred to herein as an “envelope”) caused by the spray moving throughout the vessel is obtained. The contents of buffer  530 A can be analyzed, in whole or in part, for properties or patterns that characterize the spray inside the vessel. The above description describes the operation of an exemplary structure for processing a signal obtained from first pickup  312 A. The operation of and structure for processing a signal obtained from a second pickup  312 B is essentially identical, using signal conditioner  520 B, amplifier  522 B, adjustment means  523 B, A/D converter  524 B, buffer  526 B, processor  528 B, and RMS buffer  530 B. If only a single pickup is being used, then the process can proceed directly to the sound analysis block  424  (described in more detail below) where the processed sound signals are analyzed to determine if the spray head(s) are operating properly. If two pickups are being used, however, in the preferred embodiment, signal enhancement processing is performed in signal enhancement block  422 .  
         [0034]    Typically, a pickup will be “paired” with a particular spray head or spray stream by locating the pickup in a position where it will receive the maximum sound from the spray head with which it is paired. For example, in the example illustrated in FIG. 3, spray head  304 A is paired with pickup  312 A, and spray head  304 B is paired with pickup  312 B. Since pickup  312 A is placed to optimize the sensing of sound generated by spray head  304 A (i.e., nearer to spray head  304 A), it will pick up a very strong signal from spray head  304 A when spray head  304 A is directing a spray stream directly at the sensing area of pickup  312 A. The same is true for spray head  304 B and paired pickup  312 B. For the purpose of this application, the spray head paired with a particular pickup is referred to herein as the “near head”, and all other spray heads are referred to by the term “far head” relative to that pickup.  
         [0035]    Even though pickup  312 A is placed to optimize the sensing of sound generated by spray head  304 A, it will pickup all sounds within its sensing capability. FIG. 8 illustrates the three basic categories of sounds received by the pickups. Referring to FIG. 8, category #1 sounds are the sounds created by the spray from a spray head striking its near sensing area, as illustrated by lines  801 A and  801 B. Category #2 sounds are the sounds created by the spray from a spray head striking a far sensing area, as illustrated by lines  802 A and  802 B. Category #3 sounds are all other sounds, collectively, sensed by pickups  312 A and  312 B, including sounds related to sprays from both heads striking locations other than the sensing area of the pickups, the sounds of motors, pumps and machinery in or around the vessel, ambient sounds in the building in which the vessel sits (e.g., the sound of a forklift operating), and any other sounds unrelated to category #1 or category #2 sounds. The output signals from pickups  312 A and  312 B will be the RMS sum of all sound categories where the relative amplitude and spectral content of each category may vary, depending on conditions.  
         [0036]    [0036]FIG. 6A represents a typical “raw” (unprocessed) signal output from pickup  312 A. FIG. 6C represents a typical raw signal output from pickup  312 B. Referring to FIG. 6A, the area of the signal indicated by  602 A and  606 A represent the category #1 sound component caused by spray from the near spray head ( 304 A) striking the sensing area around pickup  312 A (represented by line  801 A in FIG. 8). The area of the signal indicated by  604 A represents the category #2 sound component caused by spray from the far spray head ( 304 B) striking the sensing area around pickup  312 A (represented by line  802 A in FIG. 8). The area of the signal indicated by  608 A,  610 A and  612 A represents category #3 sound components caused by other sources (represented by line  803 A in FIG. 8).  
         [0037]    Referring now to FIG. 6C, the area of the signal indicated by  604 C represents the category #1 sound components caused by the spray from the near spray head ( 304 B) striking the sensing area around pickup  312 B (represented by line  801 B in FIG. 8). The area of the signal indicated by  602 C and  606 C represents the category #2 sound components caused by the spray from the far spray head ( 304 A) striking the sensing area around pickup  312 B (represented by line  802 B in FIG. 8), The area of the signal indicated by  608 C,  610 C and  612 C represents the category #3 sound components caused by other sources (represented by line  803 B in FIG. 8).  
         [0038]    Depending on the analysis process to be used, some of the sound categories included in the raw signals may be undesirable or even detrimental to the goal of monitoring the operation of the spray heads. For example, to evaluate the signal from pickup  312 A for sound properties specific to near spray head  304 A, it is necessary to differentiate the sounds associated with spray head  304 A from all other sounds comprising the raw signal. In some cases, the category #3 sound component of the raw signal is much greater than the category #1 sound component. This may be due to either extremely noisy environments, such as processing plants where a significant amount of machinery is used, or to the relatively weak spray streams produced by very small spray devices. The category #3 sound component may also have similar amplitude and spectral components as category #1 sound components making it more difficult to differentiate category #1 sound components. In order to more effectively be able to analyze the category #1 sound components, enhancing or separating the category #1 sound components from the composite signal can be performed as described below.  
         [0039]    [0039]FIGS. 6B and 6D represent an image of the raw signals illustrated in FIGS. 6A and 6C, respectively, after they have been processed. They are typical of the images stored in buffers  534 A and  534 B (FIG. 5), after the raw signals of FIGS. 6A and 6C are processed in blocks  520 A through  530 A and blocks  520 B through  530 B. Since the image stored in buffers  534 A and  534 B represents the time RMS value of the digitized raw signal, it reflects all of the components found in the raw signal. Peaks  602 B and  606 B represent the desired category #1 sound component of the raw signal. In order to effectively analyze the category #1 sound component it can be separated from the composite signal. One method of doing this is by combining the signal from FIG. 6B with the inverted signal from FIG. 6D. Since peaks  608 A and  608 D represent category #3 sound components, they are essentially equal and thus, when peaks  608 D are inverted (out of phase), they will cancel in the summing process described below. The same is true for peaks  610 A and  610 B, and  612 A and  612 B. There is also a DC offset component associated with FIG. 6B and FIG. 6D that represents the time RMS value of the background noise (steady state noise). Background noise is a category #3 sound component, is common to both pickups, and thus cancels in the summing process. What remains after summing are the peaks identified in FIGS. 6B and 6D as  602 B,  606 B, and  604 D. FIG. 7 shows a series of positive and negative peaks that represent the result of this summing process. The positive going peaks shown in FIG. 7 as  702  and  706  are due to peaks  602 B and  606 B and represent they spray from head  304 A passing the sensing area of pickup  312 A. The negative going peak shown in FIG. 7 as  704  is due to peaks  604 D and represents the spray from head  304 B passing the sensing area of pickup  312 B. FIG. 7 items  708 ,  710 , and  712  represent the canceled remnants of category #3 components  608 B,  610 B,  612 B,  608 D,  610 D, and  612 D. By separating the positive peaks into one signal and the negative peaks into another, two new signals are obtained that significantly represent the rotational performance of spray head  304 A and  304 B, respectively.  
         [0040]    One method of achieving the summing process is by use of the signal enhancement block  422  illustrated in FIG. 5. The RMS average of the latest (current) frame for each channel stored in RMS buffers  530 A and  530 B is supplied to a summing device  531 . In the example shown in FIG. 5, the signal is being processed digitally and thus, the summing device can comprise a microprocessor. The summing device  531  subtracts the value in buffer  530 B from the value in buffer  530 A. The result is then stored in buffer  532 . If the value stored in buffer  530 A is greater than the value stored in buffer  530 B, then the result stored in buffer  532  will be a positive value. If the value stored in buffer  530 A is equal to the value stored in buffer  530 B, then the result stored in buffer  532  will be 0. If the value stored in buffer  530 A is less than the value stored in buffer  530 B, then the result stored in buffer  532  will be a negative value.  
         [0041]    When the result is a positive number, it is thus known that the RMS value stored in buffer  530 A is greater than the RMS value stored in buffer  530 B, and it is thus also known that the sound sensed at the sensing area of pickup  312 A is greater than the sound sensed at the sensing area of pickup  312 B; this allows us to identify which spray head ( 304 A in this example) is being sensed at a particular time. Specifically, since it is known that the sound sensed at each pickup peaks when its sensing area is hit by the spray from its corresponding (near) spray head, then the positive peaks can be associated with spray head  304 A and the negative peaks can be associated with spray head  304 B.  
         [0042]    Since the spray heads are typically not synchronized, from time to time the peaks associated with each contact with the sensing area of the pickups will coincide, and the sum of the signals, which would normally result in a peak indicative of one of the spray heads, will be significantly reduced or all together canceled out to a zero value. For example, if the spray from spray head  304 A strikes the sensing area of pickup  312 A at the same time as the spray from spray head  304 B strikes the sensing area of pickup  312 B, and if we assume that they strike their respective sensing areas at approximately equal velocities, then when they are summed, they will cancel each other, resulting in a zero-sum condition. The time interval from one peak to the next is a function of rotational velocity of a spray head, and the time interval between one “cancellation” and another is a function of the difference in rotational velocities of the multiple spray heads. These velocities are known and thus the cancellation can be compensated for in the analysis process, for example, by programming the processor to anticipate and disregard these zero-sum conditions, or by normalizing the two signals. The normalization process involves averaging the peak amplitude in buffers  536 A and  536 B for the last “N” seconds, and then dividing the  536 A peak average by the  536 B peak average. In the cancellation caused by the “beat”, both the numerator and denominator are simultaneously reduced. Thus, both the numerator and the denominator in the normalization process are equally reduced and the normalized value remains essentially constant.  
         [0043]    By separating the positive peaks from the negative peaks, sounds sensed by pickup  312 A can be isolated from sounds sensed by pickup  312 B for purposes of analysis. The existence of peaks (and thus valleys) indicates rotational movement. Obviously, if the spray head is not moving, it will be essentially a steady constant sound signal rather than one consisting of peaks and valleys. The average amplitude of the peaks is related to the intensity of the spray. The repetition rate of the peaks is related to the rotational velocity of the spray head. To isolate the positive peaks from the negative peaks, all positive results stored in buffer  532  are input into buffer  536 A, and all negative results stored in buffer  532  are input to buffer  536 B. If it is desired to work with only positive going pulses, once the signals are isolated as described above, the sign of the value of the negative peaks stored in buffer  532  can be inverted by inverter  533  prior to being stored in peak buffer  536 B. Since consecutive frames are made with consecutive blocks of samples, they establish a new, reduced sample rate equal to the initial sample rate divided by the frame size. Each summing of the values contained in buffers  530 A and  530 B represents a sample point at the new sample rate. When distributing the sum value between buffer  536 A and buffer  536 B, their sample rate, as well as the sample rate of buffers  534 A and  534 B, must be preserved.  
         [0044]    That is, after “N” summing operations, both buffer  536 A and buffer  536 B must contain “N” samples. Therefore, for every sum value sent to one buffer, a corresponding zero value must be sent to the other buffer to hold a place value. Each sample represents one clock pulse; by inserting a zero, the timing relationship between peaks is maintained, and it provides an indication that no amplitude information of importance is present. When a sum value equals zero (i.e., the cancellation situation discussed above), a zero must be sent to both buffer A and buffer B.  
         [0045]    When the signal enhancement process is complete, there are four buffers containing sound signal data related to the sound of the spray heads in the tank: Buffer  534 A, which contains the complete RMS signal from pickup  312 A; buffer  536 A, which contains the positive-going peaks from pickup  312 A; buffer  534 B, which contains the complete RMS signal from pickup  312 B, and buffer  536 B, which contains the negative-going peaks from pickup  312 B (or, if inverted, a positive-going representation of the negative-going peaks from pickup  312 B).  
         [0046]    Using the four buffers described above gives the user of the present invention many options for analysis of the sound signals. It is understood that it is not necessary to use the outputs of all of the buffers to achieve the benefits of the present invention and, indeed, it may be desirable to use the data stored in less than all of the buffers, as described in more detail below. Obviously, if the output of certain buffers are never going to be used, these buffers and all processing steps/hardware associated with the contents of those buffers need not be included.  
         [0047]    Digital Signal Processors (DSPs)  538 A and  538 B are coupled to receive data from buffers  534 A/ 536 A and  534 B/ 536 B, respectively, as illustrated in FIG. 5. DSPs  538 A and  538 B can comprise conventional programmable math processors which can be programmed to perform various calculations and/or run various algorithms to achieve desired results.  
         [0048]    Buffers  534 A and  534 B contain the processed RMS “image” of the signal received by pickups  312 A and  312 B, respectively. The processed image is the low pass filtered envelope (a line approximating the peak values of the low pass filtered audio) of the raw audio received by the pickups. It should be remembered that this signal is not specific to any one source, but is a mix of sounds as discussed above. The processed images stored in buffers  534 A and  534 B are essentially the same as a series of repetitive peaks and valleys riding on top of a DC offset. They are used to detect the beginning and end of cycles, sound pressure levels, and pickup failures. They may be further evaluated for rotational or static properties that indicate the performance of the cleaning device.  
         [0049]    High peaks indicate the point at which the spray from a near head passes the sensing area of its respective pickup, and smaller peaks are indicative of background sound and of sound sensed from less intense sprays (e.g., those from far heads) striking the sensing area of a particular pickup. FIGS. 6A through 6D illustrate these processed images and the raw signals from which they were derived, as described more fully below.  
         [0050]    Specifically, FIG. 6A illustrates an example of an image of the raw data sensed by pickup  312 A, and FIG. 6C illustrates and example of an image of the raw data sensed by pickup  312 B. The signal conditioning performed by signal conditioners  520 A and  520 B may be used to clip out certain frequencies that are known to be outside the frequency that is known to be typical of sounds generated by the rotary cleaners being monitored (not shown), and then by RMS averaging the samples in frames of N samples as discussed above, the running low-frequency RMS representation of the spray can be drawn as an image (an envelope) as shown in FIGS. 6B (pickup  312 A) and  6 D (pickup  312 B). The peaks  602 A  602 D correspond to the sensing of the spray from spray head  304 A; peaks  604 A- 604 D correspond to the sensing of the spray from spray head  304 A; and peaks  606 A- 606 D correspond to the sensing of the spray from spray head  304 A during a second pass. Obviously FIGS.  6 A- 6 D illustrate only a portion of the stored image representation; the actual image continues over time during the cleaning cycle.  
         [0051]    As can be seen, the sensing of the sound of spray head  304 A by pickup  312 A ( 602 A,  602 B;  606 A,  606 B) is significantly larger in amplitude than is the sensing of the sound of spray head  304 A by pickup  312 B ( 602 C,  602 D;  606 C,  606 D). Similarly, the sensing of the sound of spray head  304 B by pickup  312 B ( 604 C,  604 D) is significantly larger in amplitude than the sensing of the sound of spray head  304 B by pickup  312 A ( 604 A,  604 B).  
         [0052]    There are other peak values  608 A-D,  610 A-D, and  612 A-D in FIGS.  6 A- 6 D. These peaks represent noise generated by sources other than the spray from the spray heads striking the sensing areas. Notably, the corresponding peaks (e.g.,  608 A-D) are substantially identical in amplitude, regardless as to which of the pickups senses them. This is consistent with the sensing of, for example, a sound generated by something outside of the tank and thus not “focused” on one of the sensing areas.  
         [0053]    By observing the pattern of the processed RMS image, the beginning and end of a cycle can be determined. Likewise, by monitoring the magnitude of the peak values, sound pressure level changes, indicative of fluid pressure changes can be monitored, and if all peaks suddenly stop occurring, a pickup failure can be identified.  
         [0054]    Buffers  536 A and  536 B store an enhanced image of the rotational information related to the respective spray devices. The enhanced image is acquired by canceling the other sound components (i.e., sound from other spray devices and sound from unrelated sources) as described above. The enhanced images stored in buffers  536 A and  536 B are used to detect individual device failures and are illustrated in FIG. 7. Comparing the enhanced image illustrated in FIG. 7 to the images of FIGS.  6 A- 6 D, it can be seen that peaks  702  and  706  correspond to peaks  602 A-D and  606 A-D (associated with the sensing of the spray of spray head  304 A) and peak  704  corresponds to peaks  604 A-D (associated with the sensing of spray of spray head  304 B). It is further noted that whereas the irrelevant noise peaks  608 A-D,  610 A-D, and  612 A-D of FIGS.  6 A- 6 D are visible, in the enhanced image of FIG. 7, these peaks are removed, as illustrated by the lack of any peaks at locations  708 ,  710 , and  712 .  
         [0055]    As noted above, the stored images or other stored data is analyzed to ascertain information about the operation of the spray heads. As an example, to identify a device failure a “peak ratio” analysis may be performed using DSPs  538 A and  538 B, buffers  536 A and  536 B, and standard mathematical techniques.  
       Example 1  
     Peak Ratio Analysis  
       [0056]    Peak ratio is based on a comparison of the category #1 sound components between two or more spray heads. Since the pickups are fixed in relation to the spray devices, then the physical parameters such as spry angle and spray distance that normally impact sound levels at the pickup remain unchanged. As a result, if the fluid pressure remains constant, then the energy imparted to the pickup during each pass must also be a constant. If the average imparted spray energy recorded at pickup  312 A is called “constant-A” (“average” meaning an average based on many passes of the spray over the sensing area) and the average imparted spray energy recorded at pickup  312 B is called “constant-B”, then a ratio of the two (constant-A/constant-B) will also remain essentially constant during normal operation. This calculation is based upon the assumption that both spray devices are attached to a common supply and as such are equally affected by pressure and fluid flows. Once this ratio is established it is monitored for change. If a substantial change is noted, then the ratio is evaluated to determine which spray head is at fault. Additional analysis may be performed using the contents of buffers  534 A,  534 B,  536 Aa, and  536 B to determine more information regarding the failure. Peak analysis requires comparative signals that closely reflect the energy imparted to the pickups by the passing spray. This signal can be found in the peak image stored in the buffers  536 A and  536 B.  
         [0057]    Each time a spray head directs a spray at its paired pickup, the sound level recorded at that pickup rises sharply. This offsets the sound recorded by the second pickup at the same moment in time, causing a peak of the output of summing device  531 . As discussed above, positive peaks relate to spray recorded by pickup  312 A and are stored in buffer  536 A, while negative peaks relate to spray recorded by pickup  312 B and are stored in buffer  536 B.  
         [0058]    The amplitude of the peaks is related to the intensity of the spray recorded by pickups  312 A and  312 B, respectively. Since the ratio of the spray from A to spray B under normal circumstances is essentially constant, then the ratio of the enhanced images (average peak value  536 A/average peak value  536 B) is also essentially constant. The average value of buffers  536 A and  536 B is calculated by performing a running average of the peak amplitude over the last “N” seconds stored in  536 A and  536 B, respectively, where N seconds equals a frame size of 32 seconds.  
         [0059]    The normal value for the ratio (average peak value  536 A/average peak value  536 B) is determined by performing a learn cycle on a known properly-performing wash cycle. The “normal value” is stored as the reference for future wash cycles.  
         [0060]    If device A slows, stops or clogs, the average value of  536 A will decrease and the ratio of the average value of  536 A to the average value of  536 B will also decrease, and this ratio will be less than the reference value. If device B slows, stops or clogs, the average value of  536 B decreases and the ration of the average value of  536 A to the average value of  536 B will increase, and the ratio will be greater than the reference value.  
         [0061]    By setting limits around the reference values, not only can a failure be determined, but which device failed can also be determined. These limits may either be learned by performing learn cycles on failed devices or manually established.  
       Example 2  
     Peak Sum Analysis  
       [0062]    Peak sum analysis is based upon the same basic theory as peak ratio analysis. The primary difference is that in calculating the peak ratio, the average peak value  536 A is divided by average peak value  536 B, whereas in calculating the peak sum, the average peak value  536 A and  536 B are added together.  
         [0063]    One aspect of using peak sum analysis is that when the peak sum indicates a failure it does not identify which head had failed. Regardless of which spray head fails, the failed peak sum value is always going to be less than the reference value. Thus, to determine which spray head had failed, additional analysis is necessary when two or more spray heads are in use.  
         [0064]    If spray head  304 A slows, stops or clogs, the average value stored in buffer  536 A decreases and the sum of the average value stored in buffer  536 A plus the average value stored in  536 B decreases, and the sum will be less than the reference value. If spray head  304 B slows, stops or clogs, the average value stored in  536 B decreases and the sum of the average value stored in  536 A and the average value stored in device  536 B also decreases and the sum will, again, be less than the reference value.  
         [0065]    The “normal” value for the sum equals (average peak value  536 A) plus (average peak value  536 B) and this is determined by performing a learn cycle on a known properly-operating wash cycle. The normal value is stored as the reference for future wash cycles.  
         [0066]    By setting limits around the reference, it is possible to detect a failure condition. Limits may either be learned by doing learn cycles on failed devices, or manually established. As stated above, when a failure is detected, additional analysis is required to determine which spray head has failed.  
       Example 3  
     Fast Fourier Transform Analysis  
       [0067]    Alternatively, all four buffered values can be subjected to a fast Fourier transform (FFT) in a known manner to develop spectrum corresponding to the stored signals. As noted above, each time the spray from a near head passes its associated pickup, the sound level sensed by that pickup rises sharply. Positive peaks relate to, in the above example, pickup  312 A and are stored in buffer  536 A; negative peaks relate to spray sensed at pickup  312 B and are stored in buffer  536 B. The repetition rate associated with the peaks is a function of the number of nozzles on a particular spray head (a known quantity) times the rotational velocity of the spray head. Thus, by determining the fundamental frequency (repetition rate) of the peaks, it is possible to determine the rotational velocity of the respective device.  
         [0068]    FFT is used to evaluate the spectral content of a signal. In the present invention, FFT can be used to acquire fundamental frequency values related to the peaks stored in buffers  536 A and  536 B. Using standard mathematical computation performed by, for example, DSPs  538 A and  538 B, knowledge of the frequencies and the number of nozzles on each spray head allows the calculation of this rotational velocity. The “normal” value for the rotational velocity can be determined by performing a learn cycle on a known properly-operating wash cycle and storing it as the reference for future wash cycles and comparison with the values calculated by FFT. By setting limits around the reference value, a failure condition can be detected.  
         [0069]    As noted above, in a preferred embodiment, sound signatures are first developed which comprise the collection of sound signals from the vessel when the cleaning system is known to be operating properly. This “learn cycle” develops reference parameters which are stored in a reference parameter memory  542 , which are compared with the real-time signals and data pertaining thereto as they are gathered from the system. As described above, by comparing the sound signature with the real-time “signature”, a determination can be made as to whether or not the system is operating properly. This can be performed manually, i.e., by visual examination by an operator, or it can be performed automatically using known processing methods to determine threshold differences and trigger alarms when certain thresholds are met.  
         [0070]    Reference parameter memory  542  can also be used to store historical data relating to ongoing sound measurements, as well as for storing “set up” parameters. For example, as noted above, amplifiers  522 A and  522 B have gain settings which are also determined during the learn cycle. These settings may vary from one “subcycle” to the next (e.g., a prewash cycle might have different gain settings than a final rinse cycle) and the reference parameter memory  542  can be used to store setup parameters for multiple cycles.  
         [0071]    Analysis processor  544  performs evaluation of the results of the more complex math functions carried out by the DSPs  538 A and  538 B. Analysis processor  544  receives the ongoing data from the DSPs, the reference data from reference parameter memory  542 , and compares the values using a predetermined algorithm, which algorithm may vary depending on the needs of the user.  
         [0072]    For example, at the beginning of a new subcycle the analysis processor  544  can recall the reference peak ratio value stored during the learn cycle. It can then multiply and divide the reference peak ratio value by a predetermined factor (e.g.,  8 ), and store the results in RAM. Reference value times  8  represents the upper acceptable pass/fail limit while reference divided by  8  represents the lower acceptable pass/fail limit. It will then wait for the subcycle to get up to operating speed.  
         [0073]    At this time the DSPs begins outputting the ongoing peak ratio value. The analysis processor  544  compares the ongoing peak ratio value from the DSP(s) to the reference peak value ratios stored in RAM. If the current peak ratio value is between the pass/fail limit values stored in RAM, then a “pass” condition is identified. If the current peak ratio value is outside the two values stored in RAM, then a timer can be started. If the current peak ratio value drops back between the reference values before a predetermined amount of time elapses, then the timer is reset. If the current peak ratio value remains outside the reference values and the timer times out, a fail condition is identified. Once a fail has been identified, an alarm can be activated and remain so until reset either manually or through other means.  
         [0074]    A similar process can be performed based on FFT. In this case, at the beginning of a new subcycle, the analysis processor  544  recalls the reference value(s) for the rotational velocity(s) stored during the learn cycle. It then sets limits around the reference value(s) and stores the result in RAM, and waits for the subcycle to get up to operating speed.  
         [0075]    At this time the DSPs begin outputting the ongoing rotational velocity(s). The output processor compares the values in RAM to the last ongoing rotational velocity value(s) acquired from the DSP(s). If the ongoing value is within the limits stored in RAM, then a pass is identified. If the ongoing value is greater than or less than the limits stored in RAM, a timer is activated. If the ongoing value drops back before the timer times out, then the timer is reset. If the value persists and the timer times out, a fail is identified.  
         [0076]    The overall sound level can also be monitored. In this case, at the beginning of a new subcycle the analysis processor  544  recalls the reference sound level value stored during the learn cycle. It then sets limits around the reference sound level value and stores the result in RAM, and waits for the subcycle to get up to operating speed. At this time the DSPs begin outputting the ongoing sound level values. The analysis processor  544  compares the reference values in RAM to the last sound level value acquired from the DSP(s). If the last sound level value acquired is within the limits stored in RAM, a pass is identified. If the last sound value acquired is greater than or less than the limits stored in RAM, a timer is activated. If the sound level value drops before the timer times out, the timer is reset. If the sound level value persists and the timer times out, a fail is identified. The sound levels are an indicator of fluid pressure. The higher the pressure, the higher the sound produced by the wash operation. The converse is true for low pressure. Sound levels may also be an indicator of external problems like faulty pumps or other machinery.  
         [0077]    Once pass/fail has been established, the analysis processor can activate the output devices, (i.e. relays, lights, displays, chart recorders, etc.) to alert users as to the operating condition of the system.  
         [0078]    As mentioned above, while the example given above illustrates the use of the present invention in connection with a two-head system, it is understood that systems with only one head or having more than two heads are also considered covered by the appended claims. In single head processing, the signal enhancement, peak normalization, and peak summation processes described above are not needed. Instead, analysis (e.g., FFT; zero-crossing detection based on the “AC component” obtained from RMS buffer  534 A with statistical averaging; threshold detection based on DC rectification of the AC component obtained from RMS buffer  534 A, amplitude analysis of the “AC” and “DC” components) can be performed directly.  
         [0079]    Although the present invention has been described with respect to a specific preferred embodiment thereof, various changes and modifications may be suggested to one skilled in the art and it is intended that the present invention encompass such changes and modifications as fall within the scope of the appended claims. For example, while particular methods of signal processing, signal enhancement, noise cancellation, and signal analysis are illustrated, it is understood that any known methods for achieving the results obtained by the specifically-described methods maybe utilized and fall within the scope of the present invention.