PATENT DOCUMENT

Publication Number: US-8205499-B2
Application Number: US-96166607-A
Country: US
Kind Code: B2

Title: Method and apparatus for checking an acoustic test fixture

Abstract:
A body has a first portion whose exterior surface is similar to that of a corresponding, first portion of a portable media device. An acoustic aperture is formed at a location that is similar to that of a built-in earpiece, speaker, or microphone aperture in the media device. An acoustic port is formed in the exterior surface of the body, and is adapted to be coupled to a sound test tool. An internal cavity acoustically couples the acoustic port to the acoustic aperture. Other embodiments are also described and claimed.

Claims:
1. A device for checking an acoustic test fixture, comprising:
 a body having
 a first portion whose exterior surface (a) has shape and dimensions that are similar to those of the exterior surface of a first portion of a portable media device, and (b) has formed therein an acoustic aperture that is at a location, on the exterior surface, that is similar to one of a built-in earpiece, speaker, and microphone in the first portion of the portable media device, 
 a second portion, different than the first portion, whose exterior surface (a) has shape and dimensions that are similar to those of the exterior surface of a second portion of the portable media device, and (b) has formed therein a further acoustic aperture similarly located to one of a built-in earpiece, speaker, and microphone of the portable media device that is different than that of the first portion, and 
 an acoustic port formed in the exterior surface of the body, the acoustic port being adapted to be coupled to a sound test tool, the body further having an internal cavity that acoustically couples the acoustic port to one of the acoustic aperture and the further acoustic aperture. 
 
 
     
     
       2. The device of  claim 1  wherein the acoustic aperture is at a location, on the exterior surface, that is similar to that of a built-in earpiece in the first portion of the portable media device, and the acoustic port is adapted to be coupled to the output port of a reference sound source. 
     
     
       3. The device of  claim 1  wherein the acoustic aperture is at a location, on the exterior surface, that is similar to that of a built-in microphone in the first portion of the portable media device, and the acoustic port is adapted to be coupled to the input port a sound pressure level meter. 
     
     
       4. The device of  claim 1  wherein the acoustic aperture is at a location, on the exterior surface, that is similar to that of a built-in speaker in the first portion of the portable media device, and the acoustic port is adapted to be coupled to the output port of a reference sound source. 
     
     
       5. The device of  claim 1  wherein the acoustic port is acoustically coupled by the internal cavity to both of said acoustic aperture and said further acoustic aperture. 
     
     
       6. The device of  claim 1  wherein the body has a further acoustic port formed in the exterior surface of the body, the further acoustic port being adapted to be coupled to an acoustic input or output port of a sound test tool, the body having a further internal cavity that acoustically couples said further acoustic port to said further acoustic aperture. 
     
     
       7. The device of  claim 1  wherein the body has a third portion, different than the first and second portions, whose exterior surface has shape and dimensions that are similar to those of the exterior surface of a third portion of the portable media device, wherein the exterior surface of the third portion of the portable media device has formed therein an acoustic aperture of a built-in earpiece, speaker, or microphone of the portable media device that is different than that of the first and second portions. 
     
     
       8. The device of  claim 1  further comprising an acoustic resistance element incorporated in the acoustic port or in the internal cavity of the body. 
     
     
       9. The device of  claim 1  further comprising a dummy connector, in the exterior surface of the body, that corresponds to an actual built-in communications connector of the media device. 
     
     
       10. A test fixture calibrator device comprising:
 a body having a portion with a shape and dimensions similar to those of a cellular telephone handset, the body having an acoustic port formed in its exterior surface that is adapted to be coupled to an acoustic output port of a sound test tool, the body having an internal cavity that acoustically couples the acoustic port to an aperture in the exterior surface, wherein the aperture is positioned at a location, on the exterior surface of the body, that is similar to that of a built-in earpiece or speaker of the handset, and the acoustic port is adapted to be coupled to the output port of a reference sound source. 
 
     
     
       11. A test fixture calibrator device comprising:
 a body having a portion with a shape and dimensions similar to those of a cellular telephone handset, the body having an acoustic port formed in its exterior surface that is adapted to be coupled to an acoustic input port of a sound test tool, the body having an internal cavity that acoustically couples the acoustic port to an aperture in the exterior surface, wherein the aperture is positioned at a location, on the exterior surface of the body, that is similar to that of a built-in microphone of the handset, and the acoustic port is adapted to be coupled to the input port of a sound pressure level meter.

Description:
An embodiment of the invention is directed to a technique for checking or verifying the acoustic capability of a test fixture that is to be used for acoustics testing of a portable media device. 
     BACKGROUND 
     More than even before, consumers are enjoying the convenience of listening to music, watching a video, or simply carrying on a telephone conversation using portable digital media devices. Devices such as consumer grade cellular telephone handsets, palm-sized or laptop computers with wireless data networking capability, and handheld digital media players such as MP3 and DVD players, are delivering ever improving sound quality to their users. 
     To verify the performance of a cellular telephone handset, including the acoustic capabilities of its built-in receiver (also referred to here as earpiece), a manufacturer typically builds or purchases a test fixture for testing the audio and radio frequency (RF) functionalities of the handset. Reliable test results can be ensured by first calibrating the test fixture prior to using it for testing a device. 
     An acoustic measurement system or test fixture has a microphone that needs to be calibrated prior to use. Typically, the microphone is first removed from the system, and then calibrated outside the system. A reference acoustic pressure source is attached to the microphone, and then the signal produced by the microphone is measured. The measurement is stored as a reference value associated with the particular microphone, and a related electronic circuit (or microphone reading) may then be adjusted accordingly for future readings, to obtain the calibrated response from the microphone. The microphone is then installed back into the measurement system with the expectation that the system is now ready to reliably test the media devices. 
     SUMMARY 
     An embodiment of the invention is a device for checking an acoustic test fixture (also referred to as an acoustic test fixture calibrator or calibration device). The calibrator device fits into the test fixture in the same manner a unit-under-test would fit. An acoustic port is formed in the exterior surface of the calibrator device&#39;s body. The acoustic port is adapted to be coupled to an acoustic input or output port of a sound test tool. The body has an internal cavity that acoustically couples the acoustic port to an acoustic aperture in the exterior surface. The acoustic aperture is positioned and otherwise adapted to mimic a corresponding aperture (e.g., a receiver aperture) on a unit-under-test. Other embodiments are also described. 
     The calibration procedure described in the Background section above may account for microphone-to-microphone sensitivity variations (i.e., different microphones in a given set may have substantially different sensitivities), and microphone sensitivity degradation over time. However, it cannot account for variations in the installation of the microphone in a test fixture. For example, there may be manufacturing variations, among otherwise identical manufactured test fixtures, in the distance between the microphone and the installed device under test (unit-under-test), or in leakage or other acoustic losses. In accordance with an embodiment of the invention, accurate measurements may be more likely across many test fixtures, by calibrating the microphone while it is installed in the test fixture, rather than first removing it from the test fixture. Additionally, a further advantage may be obtained by moving the “calibration reference” from the microphone plane to the plane of the acoustic output aperture of the unit-under-test. Doing so allows for acoustic pressure measurements, obtained from different test fixtures and microphones, to be accurately and reliably compared. 
     Use of the calibrator devices described here avoids the need to maintain several equal “golden” media devices, for the calibration of test fixtures that have been produced or are being used in different manufacturing plants. The calibrator devices are easier to manufacture than the media devices, and it is easier to ensure that all of them are equal in terms of physical dimensions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the invention are illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment of the invention in this disclosure are not necessarily to the same embodiment, and they mean at least one. 
         FIG. 1  is an elevation view of an example portable media device. 
         FIG. 2  is an elevation view of an example acoustic test fixture for an example portable media device. 
         FIG. 3  shows the test fixture in use, while a receiver acoustic test is being performed on an example media device under test (DUT). 
         FIG. 4  shows the test fixture in use, while a speaker acoustic test is being performed on the DUT. 
         FIG. 5  shows front views of the DUT and its corresponding, test fixture calibrator. 
         FIG. 6  shows side views of the DUT and its corresponding, test fixture calibrator. 
         FIG. 7  shows the test fixture calibrator in use, while checking the acoustic test fixture, using an example sound pressure level (SPL) meter and an example reference sound source. 
         FIG. 8  shows an elevation view of another example test fixture calibrator. 
         FIG. 9  is a flow diagram of a process for checking an acoustic test fixture. 
     
    
    
     DETAILED DESCRIPTION 
     In this section we shall explain several preferred embodiments of this invention with reference to the appended drawings. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not clearly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. 
     I. Overview 
     An embodiment of the invention is described here in the following sections, using an example portable media device, an example acoustic test fixture, and a corresponding acoustic test fixture calibrator. 
     First, an example portable media device  100  to be tested (DUT, or simply media device  100 ) is described in connection with  FIG. 1 . Next, a description of an example acoustic test fixture  500 , depicted in  FIG. 2 , is given. Its use for acoustics testing of the example media device is then described in connection with  FIG. 3  and  FIG. 4 . Note that these are only examples of test fixture and a DUT—the invention is also applicable to other acoustic test fixture designs and other DUT designs. In the next section, a test fixture calibrator in accordance with an embodiment of the invention is described together with its different views in  FIG. 5  and  FIG. 6 .  FIG. 7  shows an embodiment of a calibrator in use, that corresponds to the DUT shown in  FIG. 1 . The calibrator description then continues with another example calibrator, depicted in  FIG. 8 . Lastly, a flow for a process of checking an acoustic test fixture, using the calibrator, is given in  FIG. 9 . 
     II. Example Portable Media Device (DUT) 
     Referring now to  FIG. 1 , a perspective view of a media device  100  is shown. The device  100  can be detachably mounted to or interfaced with a test fixture  500  (see  FIG. 2 ). A housing  102  includes a speaker housing acoustic aperture  122  that may be located in proximity to a lower portion of the media device  100  (referred to here as the bottom end). The bottom end may also contain a microphone, with associated microphone acoustic aperture  114  in the housing  102 . In certain embodiments, the microphone aperture  114  and/or the speaker aperture  122  may be located on a bottom face  124  of the media device  100 . More generally, the microphone aperture  114  and the speaker aperture  122  may be located on any other portion of the housing  102  that can facilitate the delivery and reception of sound in the manner in which the device  100  is intended to be used. 
     In one embodiment, the housing  102  includes a first housing portion  104  and a second housing portion  106  that are fastened together to encase various electronic components of the media device  100 . The housing  102  may be made of polymer-based materials that are formed by, for instance, injection molding to define the form factor of the media device  100 . The housing  102  may surround and/or support internal components, such as circuit boards having integrated circuit components, internal radio frequency circuitry, an internal antenna, a speaker, a microphone, a receiver (earpiece), nonvolatile mass storage such as nonvolatile solid state memory and/or a magnetic rotating disk drive, as well as other components. The housing  102  also provides for the mounting of a built-in display  108 , a separate keypad (not shown), an earphone jack  116 , and a battery charging jack (not shown). As an alternative to the separate keypad,  FIG. 1  shows a device that has a single touch sensitive display  108  that spans most of the area on the front face of the device  100 , for both showing information to the user, as well as accepting input by the user. In this particular embodiment, the device  100  can be used a telephony handset, where receiver/aperture  112  is positioned at the top end of the device  100  as shown, to facilitate such use of the device. 
     The media device  100  may include a wireless communications function, such as cellular or satellite telephony, pager, portable laptop/notebook computer, or other wireless communications function. The media device  100  may be, for example, an iPod or iPhone media device, or a palm sized personal computer such as an iPAQ Pocket PC available from Hewlett Packard, Inc., of Palo Alto, Calif. In some embodiments, the media device may synchronize with a remote computing system or server, to receive media using either a wireless or wireline communication path. Media may include sound or audio files, music, video, and other digital data, in either streaming and/or discrete (e.g., files) formats. The media device  100  may also have a wireline communication connector  103 , e.g. a 30-pin connector, that may be located on the bottom face of the device  100 . This can be used to directly connect (e.g., dock) the device  100  to another computer (also referred to as a docking connector). During synchronization, a host system (e.g., the computer that is directly connected by the wireline communication connector  103 ) may provide media to a client software application embedded within the media device  100 . The media and/or data may be downloaded into the media device  100 , or the media device  100  may upload media to the remote host or another client system. 
     The primary functional blocks of the media device  100  may include the following built-in components. A processor may control the operation of many functions and other circuitry in the media device  100 . The processor may, for example, drive the display  108  and may receive user inputs through a user interface (which may include a single, touch sensitive display panel on the front face of the device  100  and circuitry to interface the microphone, speaker, and receiver). Data storage may be comprised of nonvolatile solid state memory and/or a kinetic nonvolatile storage device (e.g., rotating magnetic disk drive) that stores the different media (e.g., music and video files, functional software, preference information, e.g., for media playback, transaction information, e.g., information such as credit card information and other user authentication information, and wireless connection information, e.g., information that may enable the media device to establish wireless communication with another device). 
     In addition to the data storage, there may be memory, also referred to as main memory or program memory, to store code and data being executed by the processor. The memory may be comprised of solid state random access memory. A bus provides a data transfer path between the memory, storage and the processor. In addition, the bus may also allow communications with a coder/decoder (codec), which is a specialized circuit that converts a digital audio signal into an analog signal for driving the speaker and/or the receiver. This is designed to produce sound, including voice, music and other like audio. The codec may also convert sound detected by the microphone into digital audio signals for storage and digital processing by the processor. 
     The media device  100  also includes communications circuitry for external, wireless and wireline communications. For example, the communications circuitry may implement Wi-Fi links according to IEEE 802.11 industry standards. The communications circuitry may also include wireline network interface controllers (e.g., an Ethernet interface). These allow the media device  100  to appear and be accessed as an end node in the Internet. 
     The communications circuitry may also implement wireless communications in accordance with standards such as Bluetooth, Global System for Mobile Communications (GSM) and/or code division multiple access (CDMA) wireless protocols. These may also allow the media device to function as a conventional cellular telephony handset, allowing its user to make and receive wireless phone calls. 
     In addition, the communications circuitry may also include a direct point-to-point interface to another computer or accessory device, such as in accordance with a computer peripheral bus standard (e.g., USB), or via a 30-pin docking connector. 
     All of the above functionality may be integrated within a single housing which makes the media device  100  a portable computing device that is battery or fuel cell operated and is palm sized. In other embodiments, however, the media device  100  may be somewhat larger than palm size, e.g. a laptop or notebook computer, yet nevertheless, it is still considered a personal, consumer grade, stand alone mobile computing or media processing device. 
     The primary functional blocks have been described mostly in terms of hardware components. However, there are also several software components that control and manage, at a higher level, the different functions of the media device  100 . There may be at least two layers of user software in the media device. During the life cycle of the media device, one or more of these software components may be updated to either fix errors or enhance functionality. These user software components include an operating system, and several applications that may run on top of the operating system. Both the operating system and the applications may be residing in main memory while being executed by the processor. Other architectures for software and the underlying hardware that will execute it are possible, e.g. a processor that is cell based with multiple cell-type processing units in a data driven architecture. 
     In most instances, the operating system is typically the first user level software that will be executed after any embedded, power on self-test routines are performed by the media device  100 . After the operating system has booted, one or more applications may be automatically or manually (through user command) launched, to implement the different high level functions of the media device  100 . For instance, there may be a cellular telephone application that configures a built-in touch sensitive display to look like the keypad of a telephony handset, and allows the user to enter a telephone number to be called, or select a previously stored number from a telephone address book. The cellular application may register the media device as a cellular handset with the nearest cellular base station (using the appropriate cellular communications protocols built into the media device). The application then proceeds to allow the user to make a call, and controls the built-in microphone and receiver to enable the user to experience a two-way conversation during the cellular phone call. 
     Another application may be a browser application that allows the user to surf the Web on the built-in display and speaker, using, for example, the Wireless Access Protocol over a GSM or Wi-Fi wireless link. 
     Still another application may be a media player application, such as an MP3 audio player. This would allow the user to select songs as MP3 files that have been downloaded into the media device  100 , for playback through the built-in speaker or earphone jack. 
     Yet another one of the applications may be an acoustics test application that allows the user to command an audio test signal be generated in the device  100  and emitted through the speaker or receiver, while simultaneously displaying the spectral and/or sound level characteristics of this generated audio test signal, i.e. its expected spectral content and/or sound level. These may be measured by an external SPL meter, for instance, from the acoustic output of the built-in speaker or receiver. In addition, the acoustic test application may be designed to perform digital processing on an audio test signal sensed by the built-in microphone, and then to show the measured spectral content and/or sound level on the built-in display of the device  100 . During development of the acoustic test application, a “known good [media] device” may be used to verify that the test application is, in fact, measuring (calculating) correctly the output of the built-in microphone, in the presence of a known and calibrated audio test signal. Similarly, during development of the receiver and speaker test portions of the test application, the software may be evaluated on a known good [media] device to ensure that it can calculate and deliver to the speaker or receiver the desired audio test signal that is to be emitted by the speaker or receiver. Other types of acoustics test applications are possible. 
     III. Example Acoustic Test Fixture 
     Having described an example portable media device  100  to be tested, we now turn to the test fixture.  FIG. 2  is a plan view of a test fixture  500  that is suitable for acoustics testing of a palm-sized, portable media device, such as the iPhone device by Apple, Inc., of Cupertino, Calif. However, the concepts below also apply to acoustic test fixtures for other types of consumer grade, portable media devices including cellular telephone handsets, laptop computers, and digital media players, such as the iPod device by Apple, Inc. In this embodiment, the test fixture  500  is a portable, handheld unit whose flat bottom allows it to rest stably on a horizontal surface of a countertop during testing. Note, however, the concepts here equally apply to larger, more complex acoustic test fixtures. The fixture  500  in this case is also adapted to act as a docking station to the portable media device under test (DUT, or simply media device), by being connected to another computer via a communication cord  514 . As an alternative, this docking connection may be a wireless one. The test fixture  500  in general, may include a platform, support structure, or device holding mechanism, to enable convenient and efficient positioning and acoustic interfacing of the media device with stand alone, sound test tools. In addition, the test fixture may be designed to interface with the media device in a functionally more efficient or aesthetically pleasing position. For example, the test fixture may secure the media device in a position that allows persons who are running or observing the testing to easily read the display of the media device during the various acoustic tests described here, and not obstruct the display during the acoustic tests, while simultaneously supplying efficient acoustic channels or pathways that couple the sound test tools to the respective acoustic apertures on the surface of the installed media device. 
     Still referring to  FIG. 2 , the plan view is of an example test fixture  500  that is suitable for a media device with aspects that are similar to those of the iPhone media device. In this case, there is a first hollow or cavity  504  and a second hollow or cavity  506  formed on the top surface of the fixture  500 . These act as holsters for the media device. To test its speaker and/or microphone, the media device is installed by being lowered into the first hollow  504 , bottom end first, until it is resting against the top surface of the fixture  500  inside the hollow. The first hollow is shaped to generally conform to the bottom end of the media device so as to loosely hold the device substantially upright as shown, i.e. essentially perpendicular or slightly angled. The first hollow is defined in part by a lower, substantially horizontal surface in which are formed one or more acoustic apertures  510 . These may be formed near one end of the hollow  504 , at a location that is aligned with one or more acoustic apertures of the installed device that are associated with a built-in microphone, to form part of an internal acoustic pathway  521  through which an acoustic test signal is to travel from inside a body of the test fixture  500  into the microphone inside the media device. 
     In addition to a microphone, the bottom end of the media device may also have a built-in speaker. In such an embodiment, the lower horizontal surface that in part defines the first hollow  504  has also formed therein one or more further acoustic apertures  512  at another end. These are at a location that is aligned with one or more acoustic apertures of the installed device  100  that are associated with the speaker, to form part of an acoustic pathway  519  through which an acoustic test signal will travel from the speaker inside the device  100  into the base or body of the test fixture. 
     In this embodiment, the first hollow  504  also has a further opening in the lower horizontal surface, between the apertures  512 ,  510  as shown, through which a docking connector  508  extends from inside the body of the test fixture  400 . The docking connector  508  mates with another one, which is built into the bottom face of the media device. The docking connector  508  is connected to one end of a communication cable  514  whose other end has a further connector  516  connected to it. The latter mates with another connector that is built into a computer (not shown). 
     The test fixture also has a second hollow  506  formed on its top surface, also acting as a holster for the device. The device is installed by being lowered into the second hollow, this time top end first, until it is resting against the lower horizontal surface of the fixture within the second hollow. The second hollow  506  is shaped to generally conform to the top end of the device  100  so as to loosely hold the device upside down, substantially upright as shown, i.e. essentially perpendicular or slightly angled. The second hollow is defined in part by its lower horizontal surface in which are formed one or more acoustic apertures  526 . These may be formed near the middle of the hollow as shown, at a location that is aligned with one or more further acoustic apertures of the installed device  100  that are associated with a receiver (also referred to as an earpiece that, in one embodiment, may only be used for telephony audio), to form part of an acoustic pathway  525  through which an acoustic test signal is to travel from the receiver into the body or base of the test fixture. 
     The test fixture also has a number of acoustic test ports. There is a microphone port  520 , located in this example on one external side of the test fixture body, which may be a hole in the surface of the body that extends into the body and communicates with the acoustic pathway  521  through which the test signal is to travel into the microphone inside the device  100 . In the particular example shown, the hole is ported through an otherwise solid portion of the body, all the way to the acoustic apertures  510  of the first hollow (that line up with those of the device built-in microphone). An off the shelf reference sound pressure source  606  may be used to generate the test signal. The reference sound source  606  may have a sound output port that simply slides onto a tube that extends outward from the hole of the microphone port  520 . 
     The test fixture  500  also has a speaker port  518 , located in this example on another external side of the test fixture body. The speaker port  518  may also be a hole (in the surface of the body) that extends into the body and communicates with the acoustic pathway  519  through which the test signal is to travel from the device&#39;s built-in speaker. In the particular example shown, the hole is ported through an otherwise solid portion of the body, all the way to the acoustic aperture  512  of the first hollow  504  that line up with those of the device built-in speaker. An off the shelf sound pressure level, SPL, meter  604  may be used to measure the audio test signal. The SPL meter may have a sound input port that includes a tube, which simply slides into the hole of the speaker port  518 . 
     The test fixture  500  also has a receiver port  524 , located in this example on another external side of the test fixture body. The receiver port  524  may also be a hole (in the surface of the body) that extends into the body and communicates with the acoustic pathway  525  through which the test signal is to travel from the device&#39;s built-in receiver. In the particular example shown, the hole is ported through an otherwise solid portion of the body, all the way to the acoustic aperture  526  of the second hollow  506  that line up with those of the device built-in receiver. An off the shelf sound pressure level, SPL, meter  604  may be used to measure the audio test signal. The SPL meter has a sound input port that includes a tube, which slides into the hole of the receiver port  524 . Both the reference sound source and SPL meter may be easily removed from their ports by a user, so that they can be re-used with other test fixtures in the retail store. 
     Note that in the example embodiment of  FIG. 2 , each of acoustic pathways  519 ,  521 , and  525  are acoustically isolated from each other, e.g. by virtue of the acoustic barrier effect of the material that makes up the otherwise solid body in which the pathways  519 ,  521 , and  525  have been formed. 
     In another embodiment, the test fixture  500  also has (embedded in its body) an earphone/headphone connector (e.g., a jack plug) which mates with an earphone connector of the media device. This is used for testing the earphone signal that is generated by the media device. 
     In addition to the test fixture  500 , one or more sound tools may also be part of the overall acoustics test system. The sound tools may include an off the shelf sound pressure level, SPL, meter  604  (see  FIG. 3 ), and an off the shelf reference sound pressure source  606  (see  FIG. 7 ). The latter emits an acoustic test signal, e.g. one or more tones, having a defined spectrum and power level, that is typically identified visibly on the outside of the reference sound pressure source&#39;s housing (e.g., “1 KHz at 114 dB-SPL”). The SPL meter  604  may have a digital display that indicates certain parameters of the measured sound, e.g. in frequency and dB-SPL, at its input port. 
       FIG. 3  shows the fixture  500  in use, during an example, receiver test. Note that the device  100  has been inserted upside down, into the second hollow  506  of the test fixture  500 . In this example, the receiver test only calls for the SPL meter  604  to be connected to the receiver port  524  as shown (the reference sound source  606  need not be connected to the test fixture  500  during this test). The test signal emitted by the built-in receiver of the device  100  may also be generated by the test application running in the device  100 . The test application causes the display of the device  100  to show the characteristics of the generated test signal (e.g., as spectral and sound level ranges) during the test. These can be readily compared by the user, to what is shown on the digital display of the SPL meter  604  as being detected at the receiver port  524 . 
       FIG. 4  shows the fixture  500  in use, during an example, speaker test. The speaker test in this case only calls for the SPL meter  604  to be connected as shown (the reference sound source  606  need not be connected). The test signal emitted by the built-in speaker of the device  100  may be generated by the test application running in the device  100 . The test application causes the display of the device  100  to show the characteristics of the generated test signal (e.g., as part of spectral and sound level ranges). These can be readily compared by the user, to what is shown on the digital display of the SPL meter as being detected at the speaker port  518 . 
     IV. Example Acoustic Test Fixture Calibrator 
     Turning now to  FIG. 5 , an elevation view of an example test fixture calibrator device  400  is shown. The calibrator device  400  is shown next to its corresponding media device  100  (to be tested). As explained below, use of the calibrator  400  to check the test fixture allows the “plane of reference” for calibrating the test fixture to be, for instance, the output of the receiver of the media device  100 , at the aperture  112 . This helps better identify those manufactured test fixtures that are non-conforming. 
     The body of the calibrator device  400  has a first portion  433  whose exterior surface has shape and dimensions that are similar to those of the exterior surface of a corresponding portion of the media device  100 . Thus, in the example here, the first portion  133  of the media device  100  is the region above the top edge of the display  108 . A corresponding portion  433  of the calibrator device  400  is shown. In addition, a receiver acoustic aperture  112  is formed in the exterior surface of the first portion  133 , in this example centered on the front face of the first portion  133 . Similarly, the portion  433  of the calibrator has an acoustic aperture  412  formed on its front face, and is located (relative to the periphery of the portion  433 ) similarly as the receiver aperture  112  (relative to the periphery of the portion  133 ). Note that the shape of the aperture  412  and its location need not be exactly the same as the corresponding aperture  112 . What is desired however is that the shape and location of the aperture  112 , as well as the shape and dimensions of the calibrator device  100 , be consistent across a number of copies of such calibrator devices, to ensure consistent acoustic performance across all copies. 
     In this particular example, the body of the calibrator device  400  also has a dummy connector  403  (also referred to as a DUT-like connector) built into its exterior surface, corresponding in shape, dimensions and location to the actual connector  103  of the media device  100 . The dummy connector  403  is an alignment mechanism, rather than an actual communication connector, that helps better fit or key the calibrator device  400  to the test fixture  500 , in the same manner as the media device  100 . Again, the shape and dimensions of the dummy connector  403  need not be precisely the same as that of the actual connector  103 . However, they should be consistent in each of the calibrator devices, to ensure equal acoustic performance between all copies of the calibrator device  400 . 
     The body of the calibrator device  400  also has an acoustic port  415  formed in its exterior surface, shown in the side view of  FIG. 5  in this example as extending out from the rear face of the calibrator device  400 . The acoustic port  415  is adapted to be coupled to an acoustic input or output port of a sound test tool, such as the reference sound source  606  (see  FIG. 7 ). The port  415  could be located elsewhere on the body, so long as a sound test tool can be easily coupled to it for checking the test fixture, and then decoupled once the test fixture has been checked. 
     The body also has an internal cavity  413  as shown that acoustically couples the port  415  to the aperture  412 . The internal cavity  413  may be engineered in terms of shape, dimensions, and/or internal wall materials, so as to provide the needed acoustic coupling characteristics. The internal cavity  413  may consist of a set of simple, intersecting bores; one or more bores may have enlarged sections. Again, consistency in the construction of the internal cavity is important across all copies of the calibrator device  400 . 
     The body of the calibrator device  400  may be precision manufactured in two pieces, namely a front face piece and a rear face piece, that are joined together along the side periphery as shown. Each piece may be machined out of a chunk of fairly rigid, acoustic barrier material, such as aluminum. One half of the internal cavity may be machined out of the inside face of each piece, so that the internal cavity is formed when the two pieces are joined together. The pieces may be joined together by a snap fit, bonding or other suitable mechanism. One or more bores may be drilled into a front wall (of the front face piece) to form the aperture  412 . Similarly, one or more bores may be drilled into a rear wall (of the rear face piece) to form the port  415 . A short extension tube may be threaded into or otherwise attached to the bore that is made in the rear face, to result in the particular shape of the port  415  shown in  FIG. 6 . Other ways of manufacturing the body of the calibrator device  400  are possible. 
     Turning now to  FIG. 7 , this is a diagram of the calibrator device  400  in use, while testing the receiver acoustic pathway of the test fixture  500 . The output port of the reference sound pressure source  606  is connected to the port  415  of the device  400 . The top portion of the device  400  has been inserted into the hollow  506  of the test fixture  500  (see  FIG. 2 ). The input of the SPL meter  604  is connected to the port  524  of the test fixture  500  (see  FIG. 2 ). The reference sound pressure source  606  is thus acoustically coupled, via the device  400  and the acoustic pathway  525 , to the SPL meter  604  (see  FIG. 2 ). The device  400 , and in particular the aperture  412 , mimics the receiver aperture  112  of the media device  100  that will be tested using the test fixture  500 . This arrangement allows the measured, calibration microphone level (measured by the SPL meter), to be relative to a known, DUT acoustic output pressure while in the test fixture  500  (the latter being provided actually by the calibrator device  400 , rather than an actual DUT). The measured calibration values may thus account for most if not all variations in the acoustic measurement system, including those from test fixture  500  manufacturing variations, device positioning, microphone angle, acoustic leaks and path losses, cable connector and back stop positioning and rotations, as well as microphone sensitivity. 
     The calibrator device  400  may have more than one acoustic port, so as to allow it to be used for checking or calibrating multiple measurement microphones on the test fixture  500 . Referring now to  FIG. 8 , an elevation view of such a calibrator device  400  is shown. In this case, the device  400  has two additional acoustic ports  419  and  417  on the exterior surface of its body, each being adapted to be connected to a respective sound test tool. Port  419  in this example is adapted to be coupled to the reference sound pressure source  606 , and is acoustically coupled via internal cavity  420  of the body, to an acoustic aperture  423 . The latter is formed on the exterior surface of a different portion of the body of the device  400  (different than the first portion or top portion  412 , see  FIG. 5 ), namely one corresponding to the speaker aperture  122  in the media device  100  (see  FIG. 1 ). Installing the calibrator device  400  into the test fixture  500  so that the aperture  423  is aligned with the aperture  512  (see  FIG. 2 ), and attaching the sound reference source  606  to the port  419 , may mimic the DUT (media device  100 ) producing a sound test signal that is acoustically coupled through the path  519  and out of the test fixture  500  into the attached SPL meter  604  at port  518 . 
     As to port  417 , it is adapted to be coupled to the SPL meter  604 , and is acoustically coupled via internal cavity  418  of the body, to an acoustic aperture  421 . The latter is formed on the exterior surface of a different portion of the body of the device  400  (different than portion  412  and the one in which the aperture  423  is formed), namely one corresponding to the microphone aperture  114  in the media device  100  (see  FIG. 1 ). Installing the calibrator device  400  into the test fixture  500  so that the aperture  421  is aligned with the aperture  510  (see  FIG. 2 ), and attaching the SPL meter  604  to the port  417 , may mimic the DUT microphone (media device  100 ) receiving a sound test signal that is received into the test fixture  500  from port  520  and acoustically coupled through the path  521  and out of the test fixture  500  into the attached SPL meter  604 . 
     Additionally, the acoustic ports and/or internal cavity of the calibrator device  400  may incorporate acoustic resistance by way of channel compression, foam, mesh, screen, or channel bends. Such acoustic resistance may facilitate the operation of the reference sound pressure source  606 , by providing necessary back-pressure, and can match the acoustic path resistance of a real DUT. By adjusting the acoustic path resistance, the sound output level of the calibrator device  400  (e.g., out of the aperture  412 ) can be adjusted to more closely match that of the DUT (e.g., out of the receiver aperture  112 ). 
       FIG. 9  is a flow diagram of a process for checking a test fixture, such as the test fixture  500 , using a calibrator device, such as the calibrator device  400 , in accordance with an embodiment of the invention. The process described here may be repeated during the manufacturing of a number of such test fixtures, to for instance check each one of the manufactured specimens. The process begins with selecting one of possibly several acoustic pathways of the test fixture to verify (block  902 ). A calibrator device having a portion whose exterior shape and dimensions mimic those of a corresponding portion of the intended media device under test (DUT), is selected (block  904 ). That portion of the selected calibrator device fits with the test fixture, in the same way as the corresponding portion of the DUT would. This portion is one that is associated with the selected acoustic pathway to be checked. For instance, the DUT may have telephony capabilities, and as such the selected portion of the test fixture to verify may be the one corresponding to an end of the DUT in which a receiver aperture (earpiece aperture) is formed. 
     The selected calibrator device is then installed to the test fixture (block  906 ). Care should be taken that the calibrator device has been correctly fitted to the test fixture. If the fit is visibly off, then the test fixture may need to be re-worked or, depending on the nature of the defect in the test fixture, scrapped. 
     If the fit of the calibrator device is acceptable, then an acoustic input or acoustic output port of a sound test tool is coupled to an acoustic port of the calibrator device (block  908 ). The calibrator device has an internal cavity that acoustically couples the acoustic port to an acoustic aperture on its exterior surface. The latter is now aligned with an acoustic aperture of the test fixture (for acoustic coupling purposes). Thus, in the example here, the acoustic aperture of the calibrator device, which corresponds to the receiver aperture in the DUT, is aligned with the corresponding receiver testing aperture in the test fixture. In this case, to test the receiver pathway of the test fixture, the sound test tool that is coupled to the acoustic port of the calibrator device may be an off the shelf reference sound pressure source. 
     Once the coupled reference sound pressure source has been turned on and is emitting it&#39;s reference sound test signal, the sound test signal is propagating into the acoustic port and through the internal cavity of the calibrator device, and then out through the aperture of the calibrator device. The sound test signal is then propagating into the test fixture through the corresponding aperture. The test signal is then measured (block  910 ). This may be done in different ways. For instance, in the example test fixture  500  described above, the sound test signal may first propagate out of the body of the test fixture  500 , before being detected in some form (e.g., by an SPL meter  604  that is coupled to an acoustic port in the body of the test fixture  500 ). The calibration values for this test fixture specimen are then noted or stored, e.g. the power and spectral characteristics of the sound test signal generated by the reference sound source  606 , and the reading by the SPL meter  604  (block  912 ). 
     The above process operations in blocks  906 - 912  may be repeated, i.e. the same, selected calibrator device may be applied to a set of multiple specimens of the test fixture. These sound test signal measurements (for the set of two or more test fixtures) can then be compared and/or analyzed, and on that basis it is determined which ones of the test fixtures may need adjustments or should be scrapped altogether (the failing group), and which ones are consistent with one another or are close enough to a predetermined reading (the passing group). The passing group, and not the failing group, may then be used “as is” for actual, receiver testing of DUTs. 
     Although the above example process checks the acoustic performance of the test fixture as it relates to a built-in receiver (earpiece) of the media device  100 , the concept is also applicable to check the acoustic performance of a test fixture associated with other acoustic functions of the media device, e.g. microphone and speaker. For test fixtures that can test more than one acoustic function (e.g., the test fixture  500  which can verify receiver, microphone and speaker functions of the DUT), a single calibrator device may be devised to verify those test fixtures with respect to all of the acoustic functions. In that case, a passing test fixture may be one for which the above process has been performed for each and every one of the different acoustic functions, and the test fixture has passed each and every one of the different acoustic function checks with the same calibrator device. 
     The invention is not limited to the specific embodiments described above. For example, the internal cavities  413 ,  418 , and  420  in the body of the calibrator device  400  are depicted in  FIG. 8  as being separate from each other. However, they may alternatively be open to each other, for example as part of a single contiguous internal cavity. They also need not have any enlarged sections as shown, but instead could be made of simple intersecting bores. Also, the above described use of the calibrator device  400  to check the particular test fixture  500  is just an example. The calibrator device  400  may in general be used to check other types of acoustic test fixtures that can be used for acoustics testing of the media device  100 , including more complex test fixtures. Accordingly, other embodiments are within the scope of the claims.

Metadata:
Filing Date: 20071220
Publication Date: 20120626
Grant Date: 20120626
Priority Date: 20071220
Inventors: GREGG JUSTIN
LEE MICHAEL M.
Assignee: APPLE INC
CPC Classifications: [{"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R2499/11", "inventive": false, "first": false, "tree": "[]"}, {"code": "H04R29/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04R29/00", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 40787041