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.
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.
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'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.
Exemplary embodiments of the present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:
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' 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.
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'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'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'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
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'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'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's mobile phone. Similarly, the user'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'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
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
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
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
Referring to
The correlation between two signals x and y at time k using an exponential window is defined as:
Where
And Sxx and Syy are defined similarly as in (2) (replacing y with x for Sxx 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−⊖k{circumflex over (ρ)}(k −1)]
∂k=2xkyk
βk=αxk2α−1yk2 (3)
Where
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.
Furthermore, the numerator for y is replaced with a small constant and so is α (replacing α 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
Where Γ is a small constant, e.g. 10E−3.
Referring to
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.
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.
Referring to
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
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
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'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 f0 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>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
Referring to
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
Referring to
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
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
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):
XCorr(n, l) Σn=0NASM(n)ECM(n−l), (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:
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.
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.
This application is a continuation of U.S. patent application Ser. No. 18/092,645, filed 23 Feb. 2021, which 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.
Number | Date | Country | |
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Parent | 12555864 | Sep 2009 | US |
Child | 14054015 | US | |
Parent | 61098250 | Sep 2008 | US |
Child | 12555864 | US |
Number | Date | Country | |
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Parent | 18092645 | Jan 2023 | US |
Child | 18515254 | US | |
Parent | 17182570 | Feb 2021 | US |
Child | 18092645 | US | |
Parent | 16838277 | Apr 2020 | US |
Child | 17182570 | US | |
Parent | 16414136 | May 2019 | US |
Child | 16838277 | US | |
Parent | 15700511 | Sep 2017 | US |
Child | 16414136 | US | |
Parent | 14827332 | Aug 2015 | US |
Child | 15700511 | US | |
Parent | 14054015 | Oct 2013 | US |
Child | 14827332 | US |