Patent Publication Number: US-2023156418-A1

Title: Acoustic sealing analysis system

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 17/182,570, filed 23 Feb. 2021, which is a continuation of U.S. patent application Ser. No. 16/838,277, filed Apr. 2, 2020, which is a continuation of U.S. patent application Ser. No. 16/414,136, filed May 16, 2019, which is a continuation of U.S. patent application Ser. No. 15/700,511, filed Sep. 11, 2017, which is a continuation of U.S. patent application Ser. No. 14/827,332, filed Aug. 17, 2015, now U.S. Pat. No. 9,781,530, which is a continuation of U.S. patent application Ser. No. 14/054,015, filed Oct. 15, 2013, now U.S. Pat. No. 9,113,267, which is a Divisional Application of U.S. application Ser. No. 12/555,864, filed Sep. 9, 2009, now U.S. Pat. No. 8,600,067 and claims the benefit of U.S. Provisional Patent Application No. 61/098,250 filed Sep. 19, 2008. The disclosure of all the aforementioned references are incorporated herein by reference in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to testing the seal of an orifice-inserted device, and more particularly, though not exclusively, to a device and method for determining if an earpiece is sealed correctly in an ear canal. 
     BACKGROUND OF THE INVENTION 
     It can be difficult to communicate using an earpiece or earphone device in the presence of high-level background sounds. In many earpiece designs a transducer is placed near the ear canal opening. Ambient sound from the surrounding environment enters the ear canal with the audio content from the transducer. Environmental sounds such as traffic, construction, and nearby conversations can degrade the quality of the audio content. 
     Although audio processing technologies can adequately suppress noise, the earpiece is generally sound agnostic and cannot differentiate sounds. Thus, one method to prevent ambient sound from entering the ear is to seal or provide an acoustic barrier at the opening of the ear canal. Sealing minimizes ambient sound leakage into the ear canal, and under the correct conditions can provide a level of noise suppression under high background noise conditions. Certain types of acoustic software (e.g., communication in a noisy environment via an ear canal microphone) may require some minimum noise isolation from the ambient sound to provide adequate performance to the user. Additionally, user conditions may change substantially during the operation of the earpiece, and in some circumstances, the earpiece may become misaligned or may be fit incorrectly such that it is not sealed correctly. A method of seal detection is needed to optimize performance. 
     SUMMARY OF THE INVENTION 
     Broadly stated, embodiments are directed to a device and method to determine if an earpiece is sealing within the design specification of the device. 
     In one embodiment, the device can include a sealing section forming an acoustic barrier between a first volume and a second volume. An ear canal receiver (ECR) can be configured to generate an acoustic signal in the first volume. An Ear Canal Microphone (ECM) in the first volume can be configured to measure the acoustic signal in the first volume. The first acoustic signal emitted by the ECR can be cross-correlated with the first acoustic signal detected with the ECM to determine if the sealing section is sealed properly. 
     At least one exemplary embodiment is directed to a method of detecting sealing integrity of an earpiece comprising the steps of: providing a test signal; generating an acoustic signal corresponding to the test signal incident on an ear canal side of a sealing section; converting the acoustic signal incident on a first side of the sealing section to an electrical signal; and cross-correlating the test signal to the electrical signal where the earpiece is sealed correctly when a cross-correlation between the test signal and the electrical signal is above a threshold. 
     At least one exemplary embodiment is directed to a method of adjusting attenuation of an earpiece comprising the steps of: relating cross-correlation of a test signal and a measured acoustic signal in an ear canal of a user to an attenuation level of a sealing section of the earpiece; comparing the attenuation level of the sealing section of the earpiece to a minimum attenuation value; and adjusting a pressure of the sealing section to meet the minimum attenuation value. 
     At least one exemplary embodiment is directed to a device comprising: a sealing section configured to seal a user&#39;s orifice, where the sealing section is configured to produce an acoustic seal between a first side of the sealing section and a second side of the sealing section; a transducer configured to generate a first acoustic signal incident on the first side of the sealing section; and a first microphone configured to measure a second acoustic signal incident on the second side of the sealing section, where the second acoustic signal includes at least a portion of the first acoustic signal that has passed from the first side to the second side of the sealing section where the first acoustic signal is compared to the second acoustic signal to determine if the sealing section is sealed. 
     Further areas of applicability of exemplary embodiments of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG.  1    is a diagram of an earpiece inserted in an ear canal in accordance with an exemplary embodiment; 
         FIG.  2    is a block diagram of optional components of an earpiece in accordance with an exemplary embodiment; 
         FIG.  3    is a flowchart of a method for checking an ear seal in accordance with an exemplary embodiment; 
         FIG.  4    is a flowchart to determine acoustic seal integrity of an earpiece in accordance with the exemplary embodiment. 
         FIG.  5    is a flowchart of a method to estimate the instantaneous cross-correlation between a first and second audio signal. 
         FIG.  6    is a flowchart to determine when to emit a test signal in accordance with an exemplary embodiment; 
         FIG.  7    is a graph illustrating different seal measurements in accordance with the present invention; 
         FIG.  8    is a block diagram for a method of adjusting the IMS system in accordance with at least one exemplary embodiment; 
         FIG.  9    is a block diagram for a method of adjusting IMS pressure in accordance with at least one exemplary embodiment; 
         FIG.  10    illustrates a sample relationship between EarSeal attenuation and XCorr in accordance with at least one exemplary embodiment; 
         FIG.  11    illustrates a flowchart of an exemplary method to determine a test signal fundamental; 
         FIG.  12    illustrates a flowchart of an exemplary embodiment to determine tonal presence in audio content; 
         FIG.  13    illustrates a flowchart of a method to determine when to emit the test signal; 
         FIG.  14    illustrates a flowchart of an exemplary method to determine acoustic seal integrity; 
         FIGS.  15 A and  15 B  illustrate a method of varying the seal of an inflation system in accordance with at least one exemplary embodiment; and 
         FIG.  16    illustrates the sending of a signal to an inflation controller upon detection of a seal fail to modify the seal pressure in accordance with at least one exemplary embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of exemplary embodiment(s) is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. 
     Exemplary embodiments are directed to or can be operatively used on various wired or wireless orifice inserted devices for example earpiece devices (e.g., earbuds, headphones, ear terminals, behind the ear devices or other acoustic devices as known by one of ordinary skill, and equivalents). 
     Processes, techniques, apparatus, and materials as known by one of ordinary skill in the art may not be discussed in detail but are intended to be part of the enabling description where appropriate. For example specific computer code may not be listed for achieving each of the steps discussed, however one of ordinary skill would be able, without undo experimentation, to write such code given the enabling disclosure herein. Such code is intended to fall within the scope of at least one exemplary embodiment. 
     Additionally exemplary embodiments are not limited to earpieces, for example some functionality can be implemented on other systems with speakers and/or microphones for example computer systems, PDAs, BlackBerry® smart phones, cell and mobile phones, and any other device that emits or measures acoustic energy. Additionally, exemplary embodiments can be used with digital and non-digital acoustic systems. Additionally various receivers and microphones can be used, for example MEMs transducers, diaphragm transducers, for example Knowles&#39; FG and EG series transducers. 
     Notice that similar reference numerals and letters refer to similar items in the following figures, and thus once an item is defined in one figure, it may not be discussed or further defined in the following figures. 
     In all of the examples illustrated and discussed herein, any specific values, for example the sound pressure level change, should be interpreted to be illustrative only and non-limiting. Thus, other examples of the exemplary embodiments could have different values. 
     Note that herein when referring to correcting or preventing an error or damage (e.g., hearing damage), a reduction of the damage or error and/or a correction of the damage or error are intended. 
     At least one exemplary embodiment of the invention is directed to an earpiece for sealing or partially sealing an ear.  FIG.  1    is a diagram of an earpiece inserted in an ear canal  124  in accordance with at least one exemplary embodiment of the invention.  FIG.  1    also illustrates portions of the ear including pinna  128 , ear canal  124  and eardrum  126 . As illustrated, the earpiece comprises an electronic housing unit  100  and a sealing unit  108 . The earpiece depicts an electro-acoustical assembly for an in-the-ear acoustic assembly, as it would typically be placed in an ear canal  124  of a user  130 . The earpiece is an in-ear earpiece, behind the ear earpiece, receiver in the ear, partial-fit device, or any other suitable earpiece type. The earpiece can partially or fully occlude the ear canal  124 . 
     The earpiece includes an Ambient Sound Microphone (ASM)  120  to capture ambient sound, an Ear Canal Receiver (ECR)  114  to deliver audio to an ear canal  124 , and an Ear Canal Microphone (ECM)  106  to capture and assess a sound exposure level within the ear canal  124 . The earpiece can partially or fully occlude the ear canal  124  to provide various degrees of acoustic isolation. The assembly is designed to be inserted into the user&#39;s ear canal  124 , and to form an acoustic seal with the walls of the ear canal  124  at a location between the entrance to the ear canal  124  and the tympanic membrane (or ear drum)  126 . In general, such a seal is typically achieved by means of a soft and compliant housing of the sealing unit  108 . Additionally, the sealing unit  108  can be a pressurized expandable element that fills a portion of the available local space. 
     Sealing unit  108  is an acoustic barrier having a first side corresponding to ear canal  124  and a second side corresponding to the ambient environment. In at least one exemplary embodiment, sealing unit  108  includes an ear canal microphone tube  110  and an ear canal receiver tube  112 . Sealing unit  108  creates a closed cavity of approximately 5 cc or less between the first side of sealing unit  108  and the tympanic membrane  126  in ear canal  124 . In at least one exemplary embodiment the sealing facilitates using the ECR (speaker)  114  to generate a full range bass response when reproducing sounds for the user. This seal also serves to significantly reduce the sound pressure level at the user&#39;s eardrum  126  resulting from the sound field at the entrance to the ear canal  124 . This seal is also a basis for a sound isolating performance of the electro-acoustic assembly. 
     In at least one exemplary embodiment and in broader context, the second side of sealing unit  108  corresponds to the side adjacent to electronic housing unit  100 . Ambient sound microphone  120  is housed in electronic housing unit  100  and is exposed to the ambient environment for receiving sound from the ambient environment around the user. 
     The electronic housing unit  100  can include various system components such as a microprocessor  116 , memory  104 , battery  102 , ECM  106 , ASM  120 , ECR,  114 , and user interface  122 , or these components can reside in a separate system or interface operatively connected. Microprocessor  116  (or processor  116 ) can be a logic circuit, a digital signal processor, controller, or the like for performing calculations and operations for the earpiece. Microprocessor  116  is operatively coupled to memory  104 , ECM  106 , ASM  120 , ECR  114 , and user interface  122 . An optional wire  118  can provide an external connection to the earpiece. Battery  102  powers the circuits and transducers of the earpiece. Battery  102  can be a rechargeable or replaceable battery. 
     In at least one exemplary embodiment, electronic housing unit  100  is adjacent to sealing unit  108 . Openings in electronic housing unit  100  receive ECM tube  110  and ECR tube  112  to respectively couple to ECM  106  and ECR  114 . ECR tube  112  and ECM tube  110  acoustically couple signals to and from ear canal  124 . For example, ECR  114  outputs an acoustic signal through ECR tube  112  and into ear canal  124  where it is received by the tympanic membrane  126  of the user of the earpiece. Conversely, ECM  106  receives an acoustic signal present in ear canal  124  though ECM tube  110 . 
     One function of ECM  106  is that of measuring the sound pressure level in the ear canal cavity  124  as a part of testing the hearing acuity of the user as well as confirming the integrity of the acoustic seal and the working condition of the earpiece. In one arrangement, ASM  120  is used to monitor sound pressure at the entrance to the occluded or partially occluded ear canal  124 . All transducers shown can receive or transmit audio signals to a processor  116  that undertakes audio signal processing and provides a transceiver for audio via the wired (wire  118 ) or a wireless communication path. Note also that the acoustic signals can be stored for later retrieval. 
     In at least one exemplary embodiment the earpiece can be constructed to actively monitor a sound pressure level both inside and outside an ear canal  124 . In at least one exemplary embodiment monitored data can be used to enhance spatial and timbral sound quality while maintaining supervision to ensure safe sound reproduction levels. In at least one exemplary embodiment an earpiece can facilitate at least one of conducting listening tests, filtering sounds in the environment, monitoring warning sounds in the environment, presenting notification based on identified warning sounds, maintaining constant audio content to ambient sound levels, and filtering sound in accordance with a Personalized Hearing Level (PHL). 
     The earpiece can generate an Ear Canal Transfer Function (ECTF) to model the ear canal  124  using ECR  114  and ECM  106 , as well as an Outer Ear Canal Transfer function (OETF) using ASM  120 . For instance, the ECR  114  can deliver an impulse within the ear canal  124  and generate the ECTF via cross correlation of the impulse with the impulse response of the ear canal  124 . The earpiece can also determine a sealing profile with the user&#39;s ear to compensate for any leakage. In at least one exemplary embodiment the earpiece can use either the ASM  120  or the ECM  106  to monitor the sound pressure level, which can then be used in a Sound Pressure Level Dosimeter calculation, to estimate sound exposure and recovery times. This permits the earpiece to safely administer and monitor sound exposure to the ear. 
     Referring to  FIG.  2   , a block diagram of an earpiece  201  in accordance with an exemplary embodiment is shown. A power supply  205  (e.g., USB power connection, hearing aid battery (batteries)) powers components of the earpiece  201  including microprocessor  206  (or processor  206 , e.g., Texas Instruments TMS320C6713) and a data communication system  216  (e.g., RF or Bluetooth communication chip). As illustrated, the earpiece  201  includes the processor  206  operatively coupled to data communication system  216 , ASM  210 , ECR  212 , and ECM  208 . Data communication system  216  may include one or more Analog to Digital Converters and Digital to Analog Converters (DAC). The processor  206  can utilize computing technologies such as a microprocessor, Application Specific Integrated Chip (ASIC), and/or digital signal processor (DSP) with associated Random Access Memory (RAM)  202  and Read Only Memory (ROM)  204 . Other memory types such as Flash, non-volatile memory, SRAM, DRAM or other like technologies can be used for storage with processor  206 . The processor  206  can also include a clock to record a time stamp. 
     In general, data communication system  216  is a communication pathway to components of the earpiece  201  and components external to the earpiece  201 . The communication link can be wired or wireless. In at least one exemplary embodiment, data communication system  216  is configured to communicate with ECM  208 , ASM  210 , visual display  218 , and user control interface  214  of the earpiece  201 . As shown, user control interface  214  can be wired or wirelessly connected. In at least one exemplary embodiment, data communication system  216  is capable of communication to devices exterior to the earpiece  201  such as the user&#39;s mobile phone  234 , a second earpiece  222 , and a portable media player  228 . Portable media player  228  can be controlled by a manual user control  230 . 
     The user&#39;s mobile phone  234  includes a mobile phone communication system  224 . A microprocessor  226  is operatively coupled to mobile phone communication system  224 . As illustrated multiple devices can be wirelessly connected to one another such as an earpiece  220  worn by another person to the user&#39;s mobile phone. Similarly, the user&#39;s mobile phone  234  can be connected to the data communication system  216  of the earpiece  201  as well as the second earpiece  222 . This connection would allow one or more people to listen and respond to a call on the user&#39;s mobile phone  234  through their respective earpieces. 
     As illustrated, a data communication system  216  can include a voice operated control (VOX) module to provide voice control to one or more subsystems, such as a voice recognition system, a voice dictation system, a voice recorder, or any other voice related processor. The VOX module can also serve as a switch to indicate to the subsystem a presence of spoken voice and a voice activity level of the spoken voice. The VOX can be a hardware component implemented by discrete or analog electronic components or a software component. In one arrangement, the processor  206  can provide functionality of the VOX by way of software, such as program code, assembly language, or machine language. 
     The RAM  202  stores program instructions for execution on the processor  206  as well as captured audio processing data. For instance, memory RAM  202  and ROM  204  can be off-chip and external to the processor  206  and include a data buffer to temporarily capture the ambient sound and the internal sound, and a storage memory to save from the data buffer the recent portion of the history in a compressed format responsive to a directive by the processor. In at least one exemplary embodiment, the data buffer can be a circular buffer that temporarily stores audio sound at a current time point to a previous time point. It should also be noted that the data buffer is operatively connected with processor  206  to provide high speed data access. The storage memory can be non-volatile memory such as SRAM to store captured or compressed audio data. 
     Data communication system  216  includes an audio interface operatively coupled to the processor  206  and the VOX to receive audio content, for example from portable media player  228 , a cell phone, or any other communication device, and deliver the audio content to the processor  206 . The processor  206  responsive to detecting voice-operated events from the VOX can adjust the audio content delivered to the ear canal of the user of the earpiece. For instance, the processor  206  (or the VOX of data communication system  216 ) can lower a volume of the audio content responsive to detecting an event for transmitting the acute sound to the ear canal of the user. The processor  206  by way of the ECM  208  can also actively monitor the sound exposure level inside the ear canal and adjust the audio to within a safe and subjectively optimized listening level range based on voice operating decisions made by the VOX of data communication system  216 . 
     The earpiece  201  and data communication system  216  can further include a transceiver that can support singly or in combination any number of wireless access technologies including without limitation Bluetooth™, Wireless Fidelity (WiFi), Worldwide Interoperability for Microwave Access (WiMAX), and/or other short or long range communication protocols. The transceiver can also provide support for dynamic downloading over-the-air to the earpiece  201 . It should be noted also that next generation access technologies can also be used in exemplary embodiments. 
     Data communication system  216  can also include a location receiver that utilizes common technology such as a common GPS (Global Positioning System) receiver that can intercept satellite signals and therefrom determine a location fix of the earpiece  201 . 
     The power supply  205  utilizes common power management technologies such as replaceable batteries, supply regulation technologies, and charging system technologies for supplying energy to the components of the earpiece  201  and to facilitate portable applications. A motor (not shown) can be a single supply motor driver coupled to the power supply  205  to improve sensory input via haptic vibration. As an example, the processor  206  can direct the motor to vibrate responsive to an action, such as a detection of a warning sound or an incoming voice call. 
     Microprocessor  206  is operatively connected with an EarSeal Inflation Management System  232  to control the degree to which the sealing unit  108  is inflated or deflated. In one exemplary embodiment, sealing unit  108  comprises an expandable element (e.g., inflatable balloon mechanism), whereby a cavity can be filled with air or a liquid to change the degree of acoustic isolation between the internal ear canal space  124  and the ambient environment. Alternately, a passive system for sealing ear canal  124  is used such as a flexible rubber or a silicon sealing unit or a foam plug. In one exemplary embodiment, the passive system is a balloon mechanism that is filled with air or liquid. The balloon mechanism conforms to the shape and size of an ear canal and includes a restorative force module that applies a pressure to the balloon mechanism for sealing the ear canal cavity. 
     The earpiece is a single operational device or a family of devices configured in a master-slave arrangement, for example, a mobile device and an earpiece. In the latter embodiment, the components of the earpiece are reused in different form factors for the master and slave devices. 
     Referring to  FIG.  3   , a flowchart illustrates a method for an acoustic sealing analysis system in accordance with an exemplary embodiment. In general, a first volume is acoustically isolated from a second volume. The test determines if the two volumes have sufficient acoustic isolation from one another. For example, cars are designed to have a quiet interior. Users of an automobile do not want to be subjected to the noise of the external environment. Thus, a car interior (first volume) is acoustically isolated from the external environment outside of the automobile. Similarly, an earpiece having a sealing unit such as described in  FIG.  1    will create a first volume (the ear canal) that is acoustically isolated from the ambient environment of the user (second volume). In either example, the acoustic sealing analysis system determines if there is sufficient acoustic isolation for the application. In the earpiece example, random or periodic testing of the seal may be beneficial because a new seal is formed in the ear canal when the device is put in the ear or it may shift over time depending on user activity. 
     The method begins at step  302 . A test signal is acquired in a step  304 . For example, the test signal can be stored in memory or generated by a microprocessor. The test signal is provided to the acoustic transducer. The acoustic transducer or loudspeaker (such as an ECR) emits an acoustic signal corresponding to the test signal within the first volume in a step  306 . The acoustic field in the first volume is detected by an Ear Canal Microphone (ECM) in a step  308 . The acoustic loading on both the ECR and ECM will change depending on the degree of acoustic sealing, thereby affecting the degree magnitude of the radiated ECR signal detected by the ECM. In general, as the degree of ear seal decreases, the effect of lumped air mass coupled to the ECR and ECM will decrease thereby increasing in Thevenin capacitance, which effectively reduces the transfer of low frequency emitted sound from the ECR to the ECM. 
     In one exemplary embodiment, the test signal and the acoustic signal emitted by the loudspeaker into the first volume is a single frequency sine wave signal for testing leakage from one volume to another. 
     The degree of sealing between the first and second acoustic volumes is determined in a step  310  and the process ends at step  312 . The cross-correlation between the emitted test signal and detected ECM signal is taken. In at least one exemplary embodiment, the test signal and the measured acoustic signal emitted by the loudspeaker are conditioned using a time delay and frequency dependent filter. The ear-seal is determined to be low (or “leaky”) if the cross-correlated signals are below a predetermined value. In at least one exemplary embodiment, automatic adjustments to the sealing section are made (such as deflating and re-inflating the sealing balloon to reseal the sealing section including retesting). Alternately, an audible sound, vocal response, or visual response can be provided to let the user know that the earpiece is sealed correctly or incorrectly. 
     Referring to  FIG.  1   , the earpiece is used as an example to illustrate a test sequence as disclosed in  FIG.  3   . Sealing unit  108  occludes an opening of ear canal  124  creating a first volume (ear canal  124 ) and a second volume (the ambient environment). Sealing unit  108  has a first side exposed to ear canal  124  and a second side is exposed to or corresponds to the ambient environment external to the ear. 
     In at least one exemplary embodiment, processor  116  is configured to receive a test signal in memory  104 . Processor  116  generates the test signal and provides the test signal to Ear Canal Receiver  114  (ECR  114 ). ECR  114  emits the test signal into Ear Canal Receiver Tube (ECR Tube  112 ). The test signal propagates through ECR tube  112  and into ear canal  124 . Ear Canal Microphone tube  110  (ECM tube  110 ) is configured to receive an acoustic signal incident on the first side of sealing unit  108 . The test signal in ear canal  124  propagates through ECM tube  110  and is received by Ear Canal Microphone  106  (ECM  106 ). ECM  106  is configured to measure the test signal in ear canal  124  and provide the measured test signal to processor  116 . 
     As shown, electronic housing unit  100  of the earpiece is adjacent to the second side of sealing unit  108 . Electronic housing unit  100  is exposed to the ambient environment and for purposes of acoustic sealing analysis is considered the second side of sealing unit  108 . Electronic housing unit  100  includes Ambient Sound Microphone  120  (ASM  120 ), which is configured to measure sounds in the ambient environment. Thus, ASM  120  receives and measures an ambient signal corresponding to a signal incident on the second side of sealing unit  108 . ASM  120  provides the measured ambient signal to processor  116 . 
     Ideally, sealing unit  108  is an acoustic barrier preventing the test signal or very little of the test signal from getting past sealing unit  108  and into the ambient environment. Conversely, sealing unit  108  if improperly sealed will pass some of the test signal. Processor  116  compares the test signal to the signal provided by ECM  106  corresponding to the acoustic signal in ear canal  124 . In particular, processor  116  undertakes the cross-correlation between emitted test signal and the ECM signal. 
     Referring to  FIG.  4   , a flowchart of an exemplary method to determine the acoustic seal integrity of an earpiece in accordance with an exemplary embodiment is illustrated. In at least one embodiment of an acoustic sealing analysis system, the test signal is masked or used in a manner undetectable by the user. This allows unobtrusive (periodic or non-periodic) testing to determine if a device is sealed correctly ensuring optimum system performance and more importantly user safety. 
     In at least one exemplary embodiment, an audio content is provided in a step  402 . A step  404  stores the test signal in a test signal data buffer. For example, a single frequency sine wave is stored in the test signal data buffer. The output (or alternatively—input) of the test signal data buffer is optionally delayed by digital delay unit  406 . The function of delay unit  406  is to time-align the emitted test signal with the ECM signal so the cross-correlation is sensitive to changes in ear seal. 
     A step  408  stores the test ECM signal in a test signal data buffer. The output (or alternatively—input) of the ECM signal buffer can be filtered with a low-pass filter  410 . The low pass filter can be configured so that the pass-band covers the frequency of the test signal. In one exemplary configuration, the low-pass filter can be a cascaded bi-quad IIR type filter with the cut-off frequency equal to 10 Hz greater than the test signal frequency. 
     A step  412  cross-correlates the optionally delayed test signal buffer with the low-pass filtered ECM signal buffer. An exemplary method for the cross-correlation algorithm is described in  FIG.  5   . The instantaneous cross-correlation (i.e. the cross-correlation at zero-lag) value from step  412  is compared with the cross-correlation threshold value  414  using comparator unit  416 . If the instantaneous cross-correlation of the two signal buffers is less than the threshold value  414 , then the seal test status is set to FAIL  418  (i.e. an ear-seal leak is detected); otherwise, if the cross-correlation is suitably high, the seal test status is set to PASS  420 . 
     Referring to  FIG.  5   , a flowchart of an exemplary embodiment to determine the instantaneous cross-correlation between a first audio signal and a second audio signal is illustrated. The process begins at step  500 . In at least one exemplary embodiment, the first audio signal is the test signal (i.e. a sine wave) and the second signal is the low-pass-filtered ECM signal. 
     The correlation between two signals x and y at time k using an exponential window is defined as: 
     
       
         
           
             
               
                 
                   
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     Where 
         S   xy ( k )=Σ l=0   ∞   ce   −η     l     x   k-l   y   k-l   (2)
 
         c= 1− e   −η 
 
     And S xx  and S yy  are defined similarly as in (2) (replacing y with x for S xx  etc.). 
     It can be shown (see Aarts et al, 2001) that (1) can be approximated with the recursion: 
       {circumflex over (ρ)}( k )={circumflex over (ρ)}( k− 1)+γ[∂ k −β k {circumflex over (ρ)}( k− 1)]  (3)
 
       ∂ k =2 x   k   y   k  
 
       β k   =αx   k   2 α −1   y   k   2  
 
     Where 
     
       
         
           
             
               
                 
                   α 
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                       y 
                       RMS 
                     
                     
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                       RMS 
                     
                   
                 
               
               
                 
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                   x 
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                   y 
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     The cross-correlation estimate using the above recursion is modified for block-wise processing rather than the sample-by-sample basis. This modification replaces the sample values (i.e. x(k) and y(k)) with values for the N-length block mean, i.e. 
     
       
         
           
             
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                 1 
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     Furthermore, the numerator for y is replaced with a small constant and so is a (replacing a with a constant effectively un-normalizes the correlation estimate). It is found that the modified un-normalized block-wise cross-correlation accurately estimates the cross-correlation compared with using the standard cross-correlation for two signals. 
     The modified block-wise fast cross-correlation algorithm, as summarized in  FIG.  5   , comprises the following steps: 
     1. A first signal buffer  502  is accumulated. This signal buffer corresponds to the emitted test signal (i.e. the sine wave).
 
2. The RMS level of the first buffer is calculated  504  (x RMS )
 
3. The mean level of the first buffer is calculated  506 .
 
4. A second signal buffer  508  is accumulated. This signal buffer corresponds to the filtered ECM signal.
 
5. The RMS level of the second buffer is calculated  510  (y RMS ).
 
6. The mean level of the second buffer is calculated  512 .
 
7. In step  514 , γ (gamma) is approximated as:
 
     
       
         
           
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             = 
             
               Γ 
               
                 2 
                 ⁢ 
                 
                   x 
                   RMS 
                 
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                   y 
                   RMS 
                 
               
             
           
         
       
     
     Where Γ is a small constant, e.g. 10E-3.
 
8. In step  516 , ∂ k  (delta) calculated as twice the product of the first signal buffer mean and the second signal buffer mean.
 
9. In step  518 , beta is calculated as the sum of the square of the mean value of the first buffer with the sum of the square of the mean value of the second buffer.
 
10. In step  520 , the new temporary estimate of the correlation newRho_temp is calculated as: newRho_temp=(delta−beta*rho_old))
 
11. In step  522 , the new estimate of the correlation newRho is updated by summing the previous estimate of the correlation with the product of gamma and the temporary estimate of the correlation newRho_temp.
 
12. In step  524 , the “old” value of the correlation is set to the newest correlation estimate, ready for the next iteration of the update algorithm.
 
13. In step  526 , the current correlation estimate between the emitted test signal and the received and filtered ECM signal is set as equal to the value of newRho.
 
     Referring to  FIG.  6   , a flowchart of a method to determine when to emit the test signal is shown. The test signal is emitted when the test can be performed unobtrusively to the user and also provides an accurate test. In at least one exemplary embodiment, a test event to determine if an earpiece is sealed correctly is initiated via a timing methodology. In a first timing scenario, the test event occurs after a delay of a first predetermined time period when the RMS of the Audio Content (AC) is less than a RMS threshold. In a second timing scenario, the delay of the first predetermined time period is allowed to lapse without the test event occurring when the RMS of the audio content is greater than the RMS threshold. A second predetermined time period is started where the test event occurs when the RMS of the audio content is less than the RMS threshold. The test event is then initiated when the second predetermined time period is exceeded independent of the RMS of the audio content. 
     A test sequence is initiated in a step  602 . The previous seal test event resets the first digital timer in a step  604 . A time delay is generated by the loop comprising steps  606  and  608 . The first digital timer is time incremented in the step  606 . After each added time increment, the first digital timer is compared against a digital_timer_threshold1. The first digital timer is time incremented (after the time has advanced another increment) after the comparison in the step  608  if the first digital timer is less than the digital_timer_threshold1. 
     A second digital timer is reset in a step  610  when the first digital timer is greater than the digital_timer_threshold1. The second digital timer is time incremented in a step  612 . Audio content (AC) from a signal buffer is retrieved in a step  614 . The audio content can be filtered through a low pass filter in an optional step  616 . The RMS of the audio content is calculated in a step  618 . The calculated RMS of the audio content is compared against an RMS_threshold  622  in a step  620 . The second digital timer is compared against a digital_timer_threshold2 in a step  624  if the RMS of the audio content is greater than the RMS_threshold. The second digital timer is time incremented (after the time has advanced another increment) when the second digital timer is less than digital_timer_threshold2 in the step of  624 . 
     The audio content signal is mixed with the test signal when the RMS of the audio content is less than the RMS_threshold in a step  626 . Also, the audio content signal is mixed with the test signal when the second digital timer is greater than digital_timer_threshold2 in the step  624 . The modified audio signal (having the test signal mixed in) is emitted by the ECR in a step  628  for testing the sealing section of the earpiece. The first digital timer is then reset in the step  604  to begin a timing sequence for another sealing section test. 
       FIG.  7    is a graph illustrating different seal measurements in accordance with the present invention. The estimated un-normalized cross-correlation between the ECM signal and the test signal (i.e. sine wave) is shown for different sine wave frequencies from 30-80 Hz. Three different curves are provided corresponding to a good fit (i.e. a tight optimal seal providing approximately 20-30 dB of acoustic attenuation), mid or partial seal (i.e. an ear-seal that could be characterized as “half in” providing approximately 10-15 dB of acoustic attenuation), and a poor seal (i.e. an ear-seal providing less than 10 dB of acoustic attenuation). At lower test frequencies, the change in correlation is more pronounced as the degree of ear seal fitting is changed from “good” to “mid” and “poor”. From the data, the threshold used to determine whether the ear seal can be characterized as “good” is approximately −20 dB, (i.e. 0.85 of  FIG.  10    which corresponds to the value for XCorr threshold  414  in  FIG.  4   ). 
     In at least one exemplary embodiment, the test signal for testing a seal of a sealing section is less than 200 hertz. The frequency of the emitted test signal is chosen to satisfy the requirements of being able to reveal small degradations in ear seal quality. It is also beneficial if the selected test signal frequency can be acoustically masked by reproduced audio to minimize detection of the test by an earpiece user. Both of these criteria are met using a test signal frequency below 200 Hz. The sensitivity is highest from the measured data at frequencies below 50 Hz. Conversely, as the test signal frequency increases the cross-correlation difference between a “good” and “bad” acoustic seal decreases. For example, with a 40 Hz test tone, the cross-correlation for a “good” ear seal is −8 dB, and for a bad ear seal it is −68 dB (i.e. a 60 dB difference). At a test signal frequency of 80 Hz, the cross-correlation for a “good” ear seal is −8 dB and for a bad ear seal it is −38 dB (i.e. a 30 dB difference). Thus, above 200 Hz the cross-correlation difference between a “good” and “bad” acoustic seal is further reduced thereby reducing the sensitivity of the test. 
     Using the cross-correlation rather than a level differencing approach improves the accuracy and minimizes errors which occur due to user non-speech body noise, such as teeth chatter; sneezes, coughs, etc. Furthermore, such non-speech user generated noise would generate a larger sound level in the ear canal than on the outside of the same ear canal producing inaccurate results. 
       FIG.  8    is a flowchart to adjust the degree of acoustic sealing of an Inflation Management System (IMS) in accordance with an exemplary embodiment. The IMS is adjusted depending on the degree of acoustic sealing provided by an earpiece. The method begins at step  802 . The acoustic sealing is measured as disclosed in  FIG.  7    and the result provided in a step  804  to determine the cross-correlation (XCorr) between a test signal and corresponding ECM signal. In general, the higher the cross-correlation, the higher the degree of acoustic sealing. An exemplary graph showing the relationship between XCorr and acoustic sealing is given in  FIG.  10   . The degree of acoustic sealing is determined from known XCorr using a look-up (or “hash”) table or using a formula (e.g. of a polynomial form) that maps the acoustic sealing to the known XCorr value. The ambient sound level is measured in a step  806 . The ambient sound level corresponds to the noise level in proximity to the user. In general, a higher degree of attenuation is desired when the ambient sound levels are high. Conversely, at low ambient sound levels the attenuation level of the IMS may be less of an issue and comfort more of a factor. The IMS is adjusted in a step  808  to meet the attenuation needs. In general, inflating the IMS increases attenuation while deflating the IMS decreases attenuation. The method terminates at step  810 . 
     Referring to  FIG.  9   , a more detailed flowchart to adjust the degree of acoustic sealing of an Inflation Management System (IMS) is shown. In general, the attenuation increases when the pressure in the IMS is raised thereby allowing a degree of control to make adjustments. For example, an adjustment is made to increase attenuation when the background noise level rises or a seal check produces a failed result. Adjustments are made until the seal check passes. The pressure level adjustments of the IMS will fall within a comfort range of a user (e.g., between 0.1 bar and 0.3 bar gauge pressure). Typically, the pressure level is set at a minimum level to achieve a predetermined attenuation level. 
     The method begins at step  902 . The degree of acoustic sealing is determined from cross-correlation between the ECM signal and the generated test signal. The XCorr value is provided in a step  904 . In step  906 , the attenuation provided by the IMS is calculated (equation) or looked up (table) from data such as that shown in  FIG.  10   . In one exemplary embodiment, the desired attenuation value is dependent on the ambient sound level of the user. In another exemplary embodiment, the desired attenuation value is dependent on the ear-canal sound level of the user. In yet another exemplary embodiment, the desired attenuation value is dependent on the level of audio content (e.g. speech or music audio) reproduced with the earphone device. In all of the above examples, the desired attenuation value is determined by one or more of the embodiments in a step  907 . 
     The difference between the degree of acoustic sealing determined in step  906  and the desired attenuation value determined in step  907  is calculated in step  908 . The difference value in step  908  is used to determine the change in pressure of the IMS necessary to minimize the difference value in a step  910 . In at least one exemplary embodiment, the difference value of the attenuation is converted into a corresponding pressure value change (e.g. in milli-Bars) using a similar look-up table or equation method as described previously. The pressure change in the IMS is then affected with step  912  to meet the desired attenuation level. For example if the desired attenuation is a decrease of 10 dB in sound across the earpiece in the ear canal, then a pressure of a variable volume inflatable system can have a gauge pressure of about 0.15 bar. If the desired attenuation is a decrease of 20 dB across the earpiece in the ear canal then the gauge pressure can be increased to about 0.25 bar, where an increased pressure is associated with an increase in attenuation. An experimental table for each earpiece can be generated in a standard devised experimental setup (e.g. impedance tunnel) and referred to when changes are needed. The method ends at step  914 . 
     Referring to  FIG.  11   , a flowchart of an exemplary method to determine a test signal fundamental is illustrated. In at least one embodiment of an acoustic sealing analysis system, the test signal is masked or used in a manner undetectable by the user or made pleasant such that the user is unaware that the test signal is being played. This allows unobtrusive (periodic or non-periodic) testing to determine if a device is sealed correctly ensuring optimum system performance and more importantly user safety. 
     In at least one exemplary embodiment, an audio content  1102  is provided. A step  1104  stores audio content  1102  in a data buffer. In this example, audio content  1102  is music played from a media player and received via a wired or wireless connection to at least one earpiece in the user&#39;s ear. An alternate example would be that audio content  1102  is a speech audio signal from a portable telephone device or the like. 
     A step  1106  determines if the buffer of audio content  1102  comprises a strong tonal signal component. Mixing the test signal having a similar fundamental frequency as audio content  1102  will mask the test signal when played to the user. Thus, the test signal is musically in harmony with the reproduced music and results in very little perceptual degradation in sound quality. 
     A step  1108  determines whether to update or generate the first fundamental tone for the test signal. The test signal is not updated or generated if buffered audio content  402  does not contain a strong tonal signal component. A return to step  1104  fills the buffer with the next audio content  402  for analysis. 
     A step  1110  analyzes the buffer of data of audio content  1102  when it has been determined that it contains a strong tonal signal component. Step  1110  determines the fundamental frequency of the tonal signal. The fundamental tone, often referred to as the fundamental and abbreviate f 0  is the lowest frequency in a harmonic series. The fundamental frequency (also called a natural frequency) of a periodic signal is the inverse of the pitch period length. The pitch period is the smallest repeating unit of a signal. The fundamental frequency of the tonal signal can be calculated using an autocorrelation analysis. 
     In one exemplary embodiment, a mathematical operation  1114  is performed where the frequency component of the test signal is limited to a frequency range below a lower minimum and upper maximum frequency range. Fund_ratio is calculated, which is defined as a ratio of the determined fundamental frequency (F_fund) of the tonal signal from step  1110  to an upper threshold value F_fund_threshold  1112 , which in one exemplary embodiment, is a fixed constant equal to approximately 100 Hz. In general, F_fund_threshold  1112  is chosen to be a low frequency value which is above the lowest (or −3 dB) frequency that a transducer can reproduce, but below a predetermined frequency. In a comparison step  1116 , if the estimated F-fund is higher than the F_fund_threshold  1112  (ratio &gt;1), then F_fund is reduced by an integer multiple to be below F_fund_threshold  1112  corresponding to the mathematical operation of step  1118 . Otherwise, the test signal fundamental is equal to F_fund as shown in step  1120 . Although not shown, the calculated test signal fundamental is compared and determined to be greater than a predetermined threshold. 
     Referring to  FIG.  1   , in at least one exemplary embodiment, processor  116  is configured to receive or generate audio content. As mentioned previously, the audio content can from external devices such as a portable phone or a media player. Memory  104  can be used as a buffer for the audio content. Processor  116  is configured to receive the buffer of audio content from memory  104 . The steps and calculations of the block diagram of  FIG.  4    are then performed by processor  116 . The result being one of the identification of a strong tonal signal component in the buffer of audio content and the test signal fundamental or loading the buffer with new audio content and starting the process again. 
     Referring to  FIG.  12   , a flowchart of an exemplary embodiment to determine tonal presence in audio content is shown. In particular, the exemplary embodiment relates to step  1106  of  FIG.  11    that analyzes audio content stored in a buffer. The method begins at step  1202 . A step  1204  gets the audio content stored in an audio signal buffer hereinafter called the audio signal. A filter step  1206  filters the audio signal to a frequency range of interest that relates to a sealing test frequency. For example, a band pass filter in the range of 20 Hz to 500 Hz could be used to filter the audio signal where the test signal is in the lower audio frequency range. An auto-correlation step  1208  analyzes the audio signal where a strong tonal signal component is represented by peaks in the analysis results. A step  1210  generates Absolute(Acorr) which is a number representing the absolute magnitude of the peaks from the analysis. For example, Absolute(Acorr) can be the square of the results from the auto-correlation. 
     A crest_factor_Acorr  1218  is generated from the results by calculating an RMS value  1214  (or time-averaged peak value) and peak value  1216  (or time averaged peak value). In at least one exemplary embodiment, the crest_factor_Acorr  1218  is the ratio of the peak value to the RMS value of an absolute auto-correlation sequence of the audio signal. 
     A comparison step  1222  is then performed. A strong tonal presence is identified when crest_factor_Acorr  1218  is greater than a threshold Crest_factor_Acorr_threshold  1220 . Identification of the strong tonal presence indicates the audio signal would facilitate masking of the test signal to determine sealing of the device (step  1226 ). The audio signal is not used in conjunction with the test signal if crest_factor_Acorr  1218  is less than Crest_factor_Acorr_threshold  1220  (step  1224 ). The process would begin again loading a next sequence of the audio signal into the buffer for review. 
     Referring to  FIG.  1   , as mentioned previously, audio content is stored in a buffer, for example memory  104 . The audio content in the buffer is provided to processor  116 . In at least one exemplary embodiment, processor  116 , runs the analysis as described in the block diagram of  FIG.  12    thereby determining if a strong tonal presence is found in the audio content in the buffer. New audio content is loaded into the buffer (memory  104 ) if a strong tonal presence is not found beginning the procedure again. 
     Referring to  FIG.  13   , a flowchart of a method to determine when to emit the test signal is shown. The method begins at step  1302 . The test signal is emitted when the test can be performed unobtrusively to the user and also provide an accurate test. In a step  1304 , an audio signal is retrieved from a buffer. In at least one exemplary embodiment, the audio signal is received from an ECM or an ASM. The audio signal is measured to determine when the sound level is low in the ear canal, the ambient environment, or both. In general, the test signal is emitted when the sound level is low. 
     A filter step  1306  band pass filters the audio signal. In one exemplary embodiment, filter step  1306  filters the audio signal from 50 Hz to 150 Hz which corresponds to a frequency range of the test signal. In a step  1308 , the RMS of the audio signal is calculated. The audio signal is analyzed to detect when the energy within an audio frequency range is below a threshold RMS_threshold  1310 . The RMS of the audio signal is the signal level in the volume being measured. A comparison step  1312  compares the measured RMS level of the filtered audio signal against RMS_threshold  1310 . In a step  1314 , a test signal is emitted when the measured RMS value is less than RMS_threshold  1310 . No test signal is emitted when the RMS of the audio signal is greater than RMS_threshold  1310 . The method ends at step  1316 . 
     Referring to  FIG.  14   , a flowchart of an exemplary method to determine acoustic seal integrity is illustrated. For example, an earpiece seal integrity corresponds to a full or partial acoustic barrier between a first volume (ear canal) and a second volume (ambient environment). In one exemplary embodiment, the degree of acoustic seal integrity is expressed as either a PASS or FAIL status, where FAIL indicates that the acoustic seal is compromised relative to a normal operating acoustic seal. For example, an earpiece that has performed the seal test and determined that the sealing unit is not sealed correctly in the ear canal of the user can provide a signal or message indicating the problem. The user can then remove, reinsert, and retest the earpiece to ensure that the seal is within normal operating specifications. 
     The method begins at step  1402 . An acoustic test signal is provided in a first volume. In a step  1404  a transducer measures the acoustic test signal and stores it in a signal buffer. In a step  1406 , a second transducer in a second volume isolated from the first volume by an acoustic barrier measures a second acoustic signal in the second volume. A portion of the acoustic test signal passes the acoustic barrier into the second volume. The amount of the acoustic test signal passing the acoustic barrier is a measure of the seal provided by the acoustic barrier. 
     In a filter step  1408 , the measured acoustic test signal in the first volume is filtered in a frequency range corresponding to the acoustic test signal to remove signals that are not part of the test. The measured signal from the first volume is heretofore called the first volume signal. Similarly, in a step  1410 , the measured signal in the second volume is filtered in a frequency range corresponding to the acoustic test signal to remove signals not related to the test (outside the frequency range) in the second volume. The measured signal from the second volume is heretofore called the second volume signal. 
     A correlation, cross-correlation, or coherence analysis is performed on the first volume signal and the second volume signal. The correlation, cross-correlation, or coherence analysis is a measure of the similarity of the signals in the first and second volumes. In particular, the non-difference analysis measures the acoustic test signal leaking past the acoustic barrier by identifying the portion of the second volume signal that is similar to the acoustic test signal in the first volume. 
     In at least one exemplary embodiment, a correlation step  1412  is performed comprising a cross-correlation of the first volume signal and the second volume signal. In a step  1414 , the peak of the cross-correlation is identified. The peak of the cross-correlation is Absolute(XCorr). In a mathematical step  1418 , the Lag-time of Peak  1420  and the Magnitude of Peak  1422  is calculated. The Lag-time of Peak  1420  is a measure of the time delay between receiving the signals in the first and second volumes. In particular, the first volume signal should be received before the second volume signal. The Magnitude of Peak  1422  corresponds to the similarity between the signals in the first and second volumes. Thus, a larger number for Magnitude of Peak relates to more leakage of the acoustic test signal getting past the acoustic barrier. 
     Two comparisons are performed that determine if the acoustic barrier is sealed correctly based on the measured and calculated data from the first and second volumes. In a comparison step  1426 , the measured Lag-time of Peak is compared against Target Lag Limits  1424 . The measured lag-time should fall within the predetermined range (Target Lag Limits  1424 ) for the seal test to be valid. If the Lag-time of Peak is within the appropriate range then a logic 1 is provided to AND function  1432 , otherwise a logic 0 is provided. In a second comparison step  1428 , the Magnitude of Peak is compared against a Peak_threshold  1430 . If the Magnitude of Peak is greater than the Peak_threshold  1430  a logic 1 is provided to AND function  1432 . This indicates that a significant portion of the acoustic test signal is present in the second volume measurement, otherwise a logic 0 is provided. A FAIL output  1434  corresponds to a logic 1 at the output of AND function  1432 . The FAIL occurs when the Lag-time of Peak is within the predetermined range and the Magnitude of Peak is greater than the Peak_threshold indicating that the acoustic barrier is sealed improperly. All other conditions indicate a PASS output  1434  and the acoustic barrier is sealed correctly. 
     In at least one exemplary embodiment and referring briefly to  FIG.  1   , an earpiece is tested to determine if sealing unit  108  is sealed correctly to the ear canal of the user. Sealing unit  108  creates a first volume in ear canal  124  and a second volume outside the ear canal  124  in the ambient environment. A masking approach is used to perform seal testing unobtrusively to the user. The user is listening to music or speech (audio content) provided to ear canal  124  from ECR  114 . 
     The music or speech is buffered in memory  104  or memory in processor  116 . Processor  116  analyzes the audio content in the buffer to identify a strong tonal content. A test signal can be created once audio content with strong tonal content is found. The test signal will have at least one fundamental pitch corresponding to the strong tonal content and optionally further harmonics. Processor  116  also analyzes the measured signals from ECM  106  and ASM  120  to determine when to emit the test signal. Processor  116  monitors and compares the sound level in the ambient environment and ear canal  124 . Processor  116  will provide the generated test signal to ECR  114  during an optimum time for test accuracy such as when the ambient sound level is low, the ear canal sound level is low, or both. Also, processor  116  will not output the test signal if there is audio content similar to the test signal in the ear canal or ambient environment. 
     Processor  116  monitors the test conditions and then provides the test signal to ECR  114  when an accurate sealing test can be performed. ECR  114  outputs an acoustic test signal which may or may not have other audio content. ECM  106  and ASM  120  respectively measure acoustic signals in ear canal  124  and the ambient environment. Processor  116  is operatively coupled to ECM  106  and ASM  120 . The measured signals are buffered in memory  104 . 
     In an exemplary embodiment, a cross-correlation is used to measure the similarity between the signals in ear canal  124  and the ambient environment. Processor  116  performs the cross-correlation calculations using the measured acoustic signals from ECM  106  and ASM  120 . In particular, the cross-correlation is used to identify and compare the acoustic test signal present in the two volumes separated by the acoustic barrier. A cross-correlation between ASM and ECM signals is defined according to the following equation (5): 
         X Corr( n,l )= E   n=0   N ASM( n )ECM( n− 1),  (5)
 
     Where: l=0, 1, 2, . . . N 
     Where ASM(n) is the n th  sample of the ASM signal, and ECM(n−l) is the (n−l) th  sample of the ECM signal. A peak of the absolute cross-correlation is estimated using a peak-picking function and also the lag time at which this peak occurs (i.e. the index I at which this occurs). Thus, the Lag-time of Peak and the Magnitude of Peak are known and respectively compared against a Target Lag Limit range and a Peak Threshold. The user of the earpiece is notified or warned that sealing unit  108  is improperly sealed by processor  116  if the measured Lag-time of Peak is within the Target Lag Limit range and the Magnitude of Peak is greater than the Peak Threshold. 
     Like Correlation and Cross-Correlation, a coherence function is also a measure of similarity between two signals. Coherence is another non-difference comparison approach that can be used for detecting acoustic seal integrity. Coherence is defined as: 
     
       
         
           
             
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     Where Gxy is the cross-spectrum of two signals (e.g. the ASM and ECM signals), and can be calculated by first computing the cross-correlation in equation (5), applying a window function, for example a Hanning window, and transforming to the frequency domain, for example via an FFT. Gxx or Gyy is the auto-power spectrum of either the ASM or ECM signals, and can be calculated by first computing the auto-correlation (using equation 5, but where the two input signals are both from either the ASM or ECM and transforming to the frequency domain. The coherence function gives a frequency-dependent vector between 0 and 1, where a high coherence at a particular frequency indicates a high degree of coherence at this frequency, and can therefore be used to analyze test signal frequencies in the ASM and ECM signals whereby a high coherence indicates the presence of the test signal in the ambient environment (indicating leakage past the acoustic barrier). 
     Other approaches such as frequency spectrum analysis and RMS levels can also be used to determine if the earpiece is sealed correctly. Using a non-difference comparison approach such as coherence or cross-correlation between the ASM and ECM signals to determine sealing is more reliable than taking the level difference of the ASM and ECM signals. Using the cross correlation rather than a level differencing approach improves the accuracy and minimizes errors which may occur due to user non-speech body noise, such as teeth chatter, sneezes, coughs, etcetera. Furthermore, such non-speech user generated noise would generate a larger sound level in the ear canal than on the outside of the same ear canal producing inaccurate results. 
       FIGS.  15 A and  15 B  illustrate a method of varying the seal of an inflation system in accordance with at least one exemplary embodiment. In the non-limiting example, when a seal is essentially detected as being low, for example the calculated sound isolation of the system is 3 dB or less, a signal is sent to a seal varying device (e.g.,  1500 ) to vary the seal, in this case increase (i.e. increase the sound isolation of the system) the seal value. The signal can be instructions to send a current over a period of time to an actuator, which can decrease the overall volume of the system (hence increasing the pressure and effectively the sealing). For example a slider actuator such as the P-653 PILine® can be used. Which has the dimensions of 15 mm by 11 mm by 8 mm, which includes an attached electronics control board, and has a mass of 1 gram. General operation uses 5V and about 100 mamps with a typical speed of 50 to 90 mm/sec. Note that the max force of about 0.15 N but such systems can be tailored to enable pumping beyond atmospheric pressure (e.g., can increase the max force). The non limiting example illustrated in  FIGS.  15 A and  15 B  shows a slider actuator  1500 , with a moving slide  1510 , having attached a pumping arm  1560 , with a hole  1550  covering bump  1520 . Upon receipt of a signal  1505  the actuator can move  1570  such that the bump  1520  covers the hole  1550  in a bellows  1530  pump. The actuation compresses the miniature bellows  1530  pushing  1590  gas through the one-way valve  1540 , upon the back stroke the bump  1520  uncovers the hole  1550  and air rushes back into the bellows  1530  for the next pump. For example if the stroke length is 2 mm and the pump arm  1560  contact area is about 9 mm 2 then each stroke moves 18 mm 3 of volume. If an inflation system  1570  needs to be inflated more (e.g., more gas to increase sealing) then each stroke can provide an additional volume of gas of 18 mm 3 into the system increasing the inflation system  1580 . If the inflation system is initially empty (e.g., needs 1000 mm 3 of gas volume to inflate) then about 56 strokes would be needed for inflation, which is about 110 mm one direction stroke length or about 2 seconds at P-653 PILine speeds. The number of oscillations and stroke length can be determined according to the signal  1505  sent, which can be specifically tailored depending upon the electronics controlling the actuators. Note that PI- 653  is an example only. Other actuation systems can be used and controlled by signal  1505 . 
       FIG.  16    illustrates a block diagram of controlled sealing in response to a seal fail signal and/or a request for increased seal attenuation. For example, a command signal  1600  is received (e.g., a seal fail signal in which a default attenuation value is attached for example 15 dB, or a signal requesting an additional amount of attenuation) by a processor. The command signal specifies an additional amount of attenuation or that the seal has failed. An attenuation needed N is identified  1610 . For example if the current attenuation is 5 dB loss at f=500 Hz, at a pressure of 0.1 bar, and a command signal is received requesting a 10 dB loss at 500 Hz, then an experimental table is queried to find the pressure needed P which is then subtracted from the current pressure to obtain an increase in pressure DP needed. The increase in pressure is converted into a volume of gas increase needed (e.g., again referring to experimental tables based upon the inflation system volume). The volume of gas increase needed can then be directly linked with the number of cycles of an actuator pump M,  1620 . The number of requested cycles M can then be sent  1630  to the actuator control circuit to pump the designated number of cycles. The system can then retest the attenuation  1640  and if refinements are needed the process can start again. 
     While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures and functions of the relevant exemplary embodiments. For example, if words such as “orthogonal”, “perpendicular” are used the intended meaning is “substantially orthogonal” and “substantially perpendicular” respectively. Additionally although specific numbers may be quoted in the claims, it is intended that a number close to the one stated is also within the intended scope, i.e. any stated number (e.g., 90 degrees) should be interpreted to be “about” the value of the stated number (e.g., about 90 degrees). 
     Thus, the description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the exemplary embodiments of the present invention. Such variations are not to be regarded as a departure from the spirit and scope of the present invention.