Method and device for in-ear echo suppression

An earpiece (100) and acoustic management module (300) for in-ear canal echo suppression control suitable is provided. The earpiece can include an Ambient Sound Microphone (111) to capture ambient sound, an Ear Canal Receiver (125) to deliver audio content to an ear canal, an Ear Canal Microphone (123) configured to capture internal sound, and a processor (121) to generate a voice activity level (622) and suppress an echo of spoken voice in the electronic internal signal, and mix an electronic ambient signal with an electronic internal signal in a ratio dependent on the voice activity level and a background noise level to produce a mixed signal (323) that is delivered to the ear canal (131).

FIELD OF THE INVENTION

The present invention pertains to sound reproduction, sound recording, audio communications and hearing protection using earphone devices designed to provide variable acoustical isolation from ambient sounds while being able to audition both environmental and desired audio stimuli. Particularly, the present invention describes a method and device for suppressing echo in an ear-canal when capturing a user's voice when using an ambient sound microphone and an ear canal microphone.

BACKGROUND OF THE INVENTION

People use headsets or earpieces primarily for voice communications and music listening enjoyment. A headset or earpiece generally includes a microphone and a speaker for allowing the user to speak and listen. An ambient sound microphone mounted on the earpiece can capture ambient sounds in the environment; sounds that can include the user's voice. An ear canal microphone mounted internally on the earpiece can capture voice resonant within the ear canal; sounds generated when the user is speaking.

An earpiece that provides sufficient occlusion can utilize both the ambient sound microphone and the ear canal microphone to enhance the user's voice. An ear canal receiver mounted internal to the ear canal can loopback sound captured at the ambient sound microphone or the ear canal microphone to allow the user to listen to captured sound. If the earpiece is however not properly sealed within the ear canal, the ambient sounds can leak through into the ear canal and create an echo feedback condition with the ear canal microphone and ear canal receiver. In such cases, the feedback loop can generate an annoying “howling” sound that degrades the quality of the voice communication and listening experience.

SUMMARY OF THE INVENTION

Embodiments in accordance with the present invention provide a method and device for background noise control, ambient sound mixing and other audio control methods associated with an earphone. Note that although this application is filed as a continuation in part of U.S. patent application Ser. No. 16/247,186, the subject matter material can be found in U.S. patent application Ser. No. 12/170,171, filed on 9 Jul. 2008, now U.S. Pat. No. 8,526,645, application Ser. No. 12/115,349 filed on May 5, 2008, now U.S. Pat. No. 8,081,780, and Application No. 60/916,271 filed on May 4, 2007, all of which were incorporated by reference in U.S. patent application Ser. No. 16/247,186 and are incorporated by reference in their entirety herein.

In a first embodiment, a method for in-ear canal echo suppression control can include the steps of capturing an ambient acoustic signal from at least one Ambient Sound Microphone (ASM) to produce an electronic ambient signal, capturing in an ear canal an internal sound from at least one Ear Canal Microphone (ECM) to produce an electronic internal signal, measuring a background noise signal from the electronic ambient signal and the electronic internal signal, and capturing in the ear canal an internal sound from an Ear Canal Microphone (ECM) to produce an electronic internal signal. The electronic internal signal includes an echo of a spoken voice generated by a wearer of the earpiece. The echo in the electronic internal signal can be suppressed to produce a modified electronic internal signal containing primarily the spoken voice. A voice activity level can be generated for the spoken voice based on characteristics of the modified electronic internal signal and a level of the background noise signal. The electronic ambient signal and the electronic internal signal can then be mixed in a ratio dependent on the background noise signal to produce a mixed signal without echo that is delivered to the ear canal by way of the ECR.

An internal gain of the electronic internal signal can be increased as background noise levels increase, while an external gain of the electronic ambient signal can be decreased as the background noise levels increase. Similarly, the internal gain of the electronic internal signal can be increased as background noise levels decrease, while an external gain of the electronic ambient signal can be increased as the background noise levels decrease. The step of mixing can include filtering the electronic ambient signal and the electronic internal signal based on a characteristic of the background noise signal. The characteristic can be a level of the background noise level, a spectral profile, or an envelope fluctuation.

At low background noise levels and low voice activity levels, the electronic ambient signal can be amplified relative to the electronic internal signal in producing the mixed signal. At medium background noise levels and voice activity levels, low frequencies in the electronic ambient signal and high frequencies in the electronic internal signal can be attenuated. At high background noise levels and high voice activity levels, the electronic internal signal can be amplified relative to the electronic ambient signal in producing the mixed signal.

The method can include adapting a first set of filter coefficients of a Least Mean Squares (LMS) filter to model an inner ear-canal microphone transfer function (ECTF). The voice activity level of the modified electronic internal signal can be monitored, and an adaptation of the first set of filter coefficients for the modified electronic internal signal can be frozen if the voice activity level is above a predetermined threshold. The voice activity level can be determined by an energy level characteristic and a frequency response characteristic. A second set of filter coefficients for a replica of the LMS filter can be generated during the freezing and substituted back for the first set of filter coefficients when the voice activity level is below another predetermined threshold. The modified electronic internal signal can be transmitted to another voice communication device and looped back to the ear canal.

In a second embodiment, a method for in-ear canal echo suppression control can include capturing an ambient sound from at least one Ambient Sound Microphone (ASM) to produce an electronic ambient signal, delivering audio content to an ear canal by way of an Ear Canal Receiver (ECR) to produce an acoustic audio content, capturing in the ear canal by way of an Ear Canal Receiver (ECR) the acoustic audio content to produce an electronic internal signal, generating a voice activity level of a spoken voice in the presence of the acoustic audio content, suppressing an echo of the spoken voice in the electronic internal signal to produce a modified electronic internal signal, and controlling a mixing of the electronic ambient signal and the electronic internal signal based on the voice activity level. At least one voice operation of the earpiece can be controlled based on the voice activity level. The modified electronic internal signal can be transmitted to another voice communication device and looped back to the ear canal.

The method can include measuring a background noise signal from the electronic ambient signal and the electronic internal signal, and mixing the electronic ambient signal with the electronic internal signal in a ratio dependent on the background noise signal to produce a mixed signal that is delivered to the ear canal by way of the ECR. An acoustic attenuation level of the earpiece and an audio content level reproduced can be accounted for when adjusting the mixing based on a level of the audio content, the background noise level, and an acoustic attenuation level of the earpiece. The electronic ambient signal and the electronic internal signal can be filtered based on a characteristic of the background noise signal. The characteristic can be a level of the background noise level, a spectral profile, or an envelope fluctuation. The method can include applying a first gain (G1) to the electronic ambient signal, and applying a second gain (G2) to the electronic internal signal. The first gain and second gain can be a function of the background noise level and the voice activity level.

The method can include adapting a first set of filter coefficients of a Least Mean Squares (LMS) filter to model an inner ear-canal microphone transfer function (ECTF). The adaptation of the first set of filter coefficients can be frozen for the modified electronic internal signal if the voice activity level is above a predetermined threshold. A second set of filter coefficients for a replica of the LMS filter can be adapted during the freezing. The second set can be substituted back for the first set of filter coefficients when the voice activity level is below another predetermined threshold. The adaptation of the first set of filter coefficients can then be unfrozen.

In a third embodiment, an earpiece to provide in-ear canal echo suppression can include an Ambient Sound Microphone (ASM) configured to capture ambient sound and produce an electronic ambient signal, an Ear Canal Receiver (ECR) to deliver audio content to an ear canal to produce an acoustic audio content, an Ear Canal Microphone (ECM) configured to capture internal sound including spoken voice in an ear canal and produce an electronic internal signal, and a processor operatively coupled to the ASM, the ECM and the ECR. The audio content can be a phone call, a voice message, a music signal, or the spoken voice. The processor can be configured to suppress an echo of the spoken voice in the electronic internal signal to produce a modified electronic internal signal, generate a voice activity level for the spoken voice based on characteristics of the modified electronic internal signal and a level of the background noise signal, and mix the electronic ambient signal with the electronic internal signal in a ratio dependent on the background noise signal to produce a mixed signal that is delivered to the ear canal by way of the ECR. The processor can play the mixed signal back to the ECR for loopback listening. A transceiver operatively coupled to the processor can transmit the mixed signal to a second communication device.

A Least Mean Squares (LMS) echo suppressor can model an inner ear-canal microphone transfer function (ECTF) between the ASM and the ECM. A voice activity detector operatively coupled to the echo suppressor can adapt a first set of filter coefficients of the echo suppressor to model an inner ear-canal microphone transfer function (ECTF), and freeze an adaptation of the first set of filter coefficients for the modified electronic internal signal if the voice activity level is above a predetermined threshold. The voice activity detector during the freezing can also adapt a second set of filter coefficients for the echo suppressor, and substitute the second set of filter coefficients for the first set of filter coefficients when the voice activity level is below another predetermined threshold. Upon completing the substitution, the processor can unfreeze the adaptation of the first set of filter coefficients

DETAILED DESCRIPTION

Processes, techniques, apparatus, and materials as known by one of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the enabling description where appropriate, for example the fabrication and use of transducers.

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 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 for following figures.

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.

Various embodiments herein provide a method and device for automatically mixing audio signals produced by a pair of microphone signals that monitor a first ambient sound field and a second ear canal sound field, to create a third new mixed signal. An Ambient Sound Microphone (ASM) and an Ear Canal Microphone (ECM) can be housed in an earpiece that forms a seal in the ear of a user. The third mixed signal can be auditioned by the user with an Ear Canal Receiver (ECR) mounted in the earpiece, which creates a sound pressure in the occluded ear canal of the user. A voice activity detector can determine when the user is speaking and control an echo suppressor to suppress associated feedback in the ECR.

When the user engages in a voice communication, the echo suppressor can suppress feedback of the spoken voice from the ECR. The echo suppressor can contain two sets of filter coefficients; a first set that adapts when voice is not present and becomes fixed when voice is present, and a second set that adapts when the first set is fixed. The voice activity detector can discriminate between audible content, such as music, that the user is listening to, and spoken voice generated by the user when engaged in voice communication. The third mixed signal contains primarily the spoken voice captured at the ASM and ECM without echo, and can be transmitted to a remote voice communications system, such as a mobile phone, personal media player, recording device, walkie-talkie radio, etc. Before the ASM and ECM signals are mixed, they can be echo suppressed and subjected to different filters and at optional additional gains. This permits a single earpiece to provide full-duplex voice communication with proper or improper acoustic sealing.

The characteristic responses of the ASM and ECM filter can differ based on characteristics of the background noise and the voice activity level. In some exemplary embodiments, the filter response can depend on the measured Background Noise Level (BNL). A gain of a filtered ASM and a filtered ECM signal can also depend on the BNL. The (BNL) can be calculated using either or both the conditioned ASM and/or ECM signal(s). The BNL can be a slow time weighted average of the level of the ASM and/or ECM signals, and can be weighted using a frequency-weighting system, e.g. to give an A-weighted SPL level (i.e. the high and low frequencies are attenuated before the level of the microphone signals are calculated).

At least one exemplary embodiment of the invention is directed to an earpiece for voice operated control. Reference is made toFIG.1in which an earpiece device, generally indicated as earpiece100, is constructed and operates in accordance with at least one exemplary embodiment of the invention. As illustrated, earpiece100depicts an electro-acoustical assembly113for an in-the-ear acoustic assembly, as it would typically be placed in the ear canal131of a user135. The earpiece100can be an in the ear earpiece, behind the ear earpiece, receiver in the ear, open-fit device, or any other suitable earpiece type. The earpiece100can be partially or fully occluded in the ear canal, and is suitable for use with users having healthy or abnormal auditory functioning.

Earpiece100includes an Ambient Sound Microphone (ASM)111to capture ambient sound, an Ear Canal Receiver (ECR)125to deliver audio to an ear canal131, and an Ear Canal Microphone (ECM)123to assess a sound exposure level within the ear canal131. The earpiece100can partially or fully occlude the ear canal131to provide various degrees of acoustic isolation. The assembly is designed to be inserted into the user's ear canal131, and to form an acoustic seal with the walls129of the ear canal at a location127between the entrance117to the ear canal and the tympanic membrane (or ear drum)133. Such a seal is typically achieved by means of a soft and compliant housing of assembly113. Such a seal creates a closed cavity131of approximately 5 cc between the in-ear assembly113and the tympanic membrane133. As a result of this seal, the ECR (speaker)125is able to generate a full range frequency response when reproducing sounds for the user. This seal also serves to significantly reduce the sound pressure level at the user's eardrum resulting from the sound field at the entrance to the ear canal131. This seal is also a basis for a sound isolating performance of the electro-acoustic assembly.

Located adjacent to the ECR125, is the ECM123, which is acoustically coupled to the (closed or partially closed) ear canal cavity131. One of its functions is that of measuring the sound pressure level in the ear canal cavity131as 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 earpiece100. In one arrangement, the ASM111can be housed in the assembly113to monitor sound pressure at the entrance to the occluded or partially occluded ear canal. All transducers shown can receive or transmit audio signals to a processor121that undertakes audio signal processing and provides a transceiver for audio via the wired or wireless communication path119.

The earpiece100can actively monitor a sound pressure level both inside and outside an ear canal and enhance spatial and timbral sound quality while maintaining supervision to ensure safe sound reproduction levels. The earpiece100in various embodiments can conduct listening tests, filter sounds in the environment, monitor warning sounds in the environment, present notification based on identified warning sounds, maintain constant audio content to ambient sound levels, and filter sound in accordance with a Personalized Hearing Level (PHL).

The earpiece100can measure ambient sounds in the environment received at the ASM111. Ambient sounds correspond to sounds within the environment such as the sound of traffic noise, street noise, conversation babble, or any other acoustic sound. Ambient sounds can also correspond to industrial sounds present in an industrial setting, such as, factory noise, lifting vehicles, automobiles, and robots to name a few.

The earpiece100can generate an Ear Canal Transfer Function (ECTF) to model the ear canal131using ECR125and ECM123, as well as an Outer Ear Canal Transfer function (OETF) using ASM111. For instance, the ECR125can deliver an impulse within the ear canal and generate the ECTF via cross correlation of the impulse with the impulse response of the ear canal. The earpiece100can also determine a sealing profile with the user's ear to compensate for any leakage. It also includes a Sound Pressure Level Dosimeter to estimate sound exposure and recovery times. This permits the earpiece100to safely administer and monitor sound exposure to the ear.

Referring toFIG.2, a block diagram200of the earpiece100in accordance with an exemplary embodiment is shown. As illustrated, the earpiece100can include the processor121operatively coupled to the ASM111, ECR125, and ECM123via one or more Analog to Digital Converters (ADC)202and Digital to Analog Converters (DAC)203. The processor121can utilize computing technologies such as a microprocessor, Application Specific Integrated Chip (ASIC), and/or digital signal processor (DSP) with associated storage memory208such as Flash, ROM, RAM, SRAM, DRAM or other like technologies for controlling operations of the earpiece device100. The processor121can also include a clock to record a time stamp.

As illustrated, the earpiece100can include an acoustic management module201to mix sounds captured at the ASM111and ECM123to produce a mixed sound. The processor121can then provide the mixed signal to one or more subsystems, such as a voice recognition system, a voice dictation system, a voice recorder, or any other voice related processor or communication device. The acoustic management module201can be a hardware component implemented by discrete or analog electronic components or a software component. In one arrangement, the functionality of the acoustic management module201can be provided by way of software, such as program code, assembly language, or machine language.

The memory208can also store program instructions for execution on the processor121as well as captured audio processing data and filter coefficient data. The memory208can be off-chip and external to the processor121and 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 processor121. 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 can in one configuration reside on the processor121to provide high speed data access. The storage memory can be non-volatile memory such as SRAM to store captured or compressed audio data.

The earpiece100can include an audio interface212operatively coupled to the processor121and acoustic management module201to receive audio content, for example from a media player, cell phone, or any other communication device, and deliver the audio content to the processor121. The processor121responsive to detecting spoken voice from the acoustic management module201can adjust the audio content delivered to the ear canal. For instance, the processor121(or acoustic management module201) can lower a volume of the audio content responsive to detecting a spoken voice. The processor121by way of the ECM123can 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 acoustic management module201.

The earpiece100can further include a transceiver204that 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 transceiver204can also provide support for dynamic downloading over-the-air to the earpiece100. It should be noted also that next generation access technologies can also be applied to the present disclosure.

The location receiver232can utilize common technology such as a common GPS (Global Positioning System) receiver that can intercept satellite signals and therefrom determine a location fix of the earpiece100.

The power supply210can utilize common power management technologies such as replaceable batteries, supply regulation technologies, and charging system technologies for supplying energy to the components of the earpiece100and to facilitate portable applications. A motor (not shown) can be a single supply motor driver coupled to the power supply210to improve sensory input via haptic vibration. As an example, the processor121can direct the motor to vibrate responsive to an action, such as a detection of a warning sound or an incoming voice call.

The earpiece100can further represent 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 earpiece100can be reused in different form factors for the master and slave devices.

FIG.3is a block diagram of the acoustic management module201in accordance with an exemplary embodiment. Briefly, the Acoustic management module201facilitates monitoring, recording and transmission of user-generated voice (speech) to a voice communication system. User-generated sound is detected with the ASM111that monitors a sound field near the entrance to a user's ear, and with the ECM123that monitors a sound field in the user's occluded ear canal. A new mixed signal323is created by filtering and mixing the ASM and ECM microphone signals. The filtering and mixing process is automatically controlled depending on the background noise level of the ambient sound field to enhance intelligibility of the new mixed signal323. For instance, when the background noise level is high, the acoustic management module201automatically increases the level of the ECM123signal relative to the level of the ASM111to create the new signal mixed323. When the background noise level is low, the acoustic management module201automatically decreases the level of the ECM123signal relative to the level of the ASM111to create the new signal mixed323

As illustrated, the ASM111is configured to capture ambient sound and produce an electronic ambient signal426, the ECR125is configured to pass, process, or play acoustic audio content402(e.g., audio content321, mixed signal323) to the ear canal, and the ECM123is configured to capture internal sound in the ear canal and produce an electronic internal signal410. The acoustic management module201is configured to measure a background noise signal from the electronic ambient signal426or the electronic internal signal410, and mix the electronic ambient signal426with the electronic internal signal410in a ratio dependent on the background noise signal to produce the mixed signal323. The acoustic management module201filters the electronic ambient signal426and the electronic internal410signal based on a characteristic of the background noise signal using filter coefficients stored in memory or filter coefficients generated algorithmically.

In practice, the acoustic management module201mixes sounds captured at the ASM111and the ECM123to produce the mixed signal323based on characteristics of the background noise in the environment and a voice activity level. The characteristics can be a background noise level, a spectral profile, or an envelope fluctuation. The acoustic management module201manages echo feedback conditions affecting the voice activity level when the ASM111, the ECM123, and the ECR125are used together in a single earpiece for full-duplex communication, when the user is speaking to generate spoken voice (captured by the ASM111and ECM123) and simultaneously listening to audio content (delivered by ECR125).

In noisy ambient environments, the voice captured at the ASM111includes the background noise from the environment, whereas, the internal voice created in the ear canal131captured by the ECM123has less noise artifacts, since the noise is blocked due to the occlusion of the earpiece100in the ear. It should be noted that the background noise can enter the ear canal if the earpiece100is not completely sealed. In this case, when speaking, the user's voice can leak through and cause an echo feedback condition that the acoustic management module201mitigates.

FIG.4is a schematic of the acoustic management module201illustrating a mixing of the electronic ambient signal426with the electronic internal signal410as a function of a background noise level (BNL) and a voice activity level (VAL) in accordance with an exemplary embodiment. As illustrated, the acoustic management module201includes an Automatic Gain Control (AGC)302to measure background noise characteristics. The acoustic management module201also includes a Voice Activity Detector (VAD)306. The VAD306can analyze either or both the electronic ambient signal426and the electronic internal signal410to estimate the VAL. As an example, the VAL can be a numeric range such as 0 to 10 indicating a degree of voicing. For instance, a voiced signal can be predominately periodic due to the periodic vibrations of the vocal cords. A highly voiced signal (e.g., vowel) can be associated with a high level, and a non-voiced signal (e.g., fricative, plosive, consonant) can be associated with a lower level.

The acoustic management module201includes a first gain (G1)304applied to the AGC processed electronic ambient signal426. A second gain (G2)308is applied to the VAD processed electronic internal signal410. The acoustic management module201applies the first gain (G1)304and the second gain (G2)308as a function of the background noise level and the voice activity level to produce the mixed signal323, where
G1=f(BNL)+f(VAL) andG2=f(BNL)+f(VAL)

As illustrated, the mixed signal323is the sum310of the G1scaled electronic ambient signal and the G2scaled electronic internal signal. The mixed signal323can then be transmitted to a second communication device (e.g. second cell phone, voice recorder, etc.) to receive the enhanced voice signal. The acoustic management module201can also play the mixed signal323back to the ECR for loopback listening. The loopback allows the user to hear himself or herself when speaking, as though the earpiece100and associated occlusion effect were absent. The loopback can also be mixed with the audio content321based on the background noise level, the VAL, and audio content level. The acoustic management module201can also account for an acoustic attenuation level of the earpiece, and account for the audio content level reproduced by the ECR when measuring background noise characteristics. Echo conditions created as a result of the loopback can be mitigated to ensure that the voice activity level is accurate.

FIG.5is a more detailed schematic of the acoustic management module201illustrating a mixing of an external microphone signal with an internal microphone signal based on a background noise level and voice activity level in accordance with an exemplary embodiment. In particular, the gain blocks for G1and G2ofFIG.4are a function of the BNL and the VAL and are shown in greater detail. As illustrated, the AGC produces a BNL that can be used to set a first gain322for the processed electronic ambient signal311and a second gain324for the processed electronic internal signal312. For instance, when the BNL is low (<70 dBA), gain322is set higher relative to gain324so as to amplify the electronic ambient signal311in greater proportion than the electronic internal signal312. When the BNL is high (>85 dBA), gain322is set lower relative to gain324so as to attenuate the electronic ambient signal311in greater proportion than the electronic internal signal312. The mixing can be performed in accordance with the relation:
Mixed signal=(1−β)*electronic ambient signal+(β)*electronic internal signal
where (1−β) is an external gain, (β) is an internal gain, and the mixing is performed with 0<β<1.

As illustrated, the VAD produces a VAL that can be used to set a third gain326for the processed electronic ambient signal311and a fourth gain328for the processed electronic internal signal312. For instance, when the VAL is low (e.g., 0-3), gain326and gain328are set low so as to attenuate the electronic ambient signal311and the electronic internal signal312when spoken voice is not detected. When the VAL is high (e.g., 7-10), gain326and gain328are set high so as to amplify the electronic ambient signal311and the electronic internal signal312when spoken voice is detected.

The gain scaled processed electronic ambient signal311and the gain scaled processed electronic internal signal312are then summed at adder320to produce the mixed signal323. The mixed signal323, as indicated previously, can be transmitted to another communication device, or as loopback to allow the user to hear his or her self.

FIG.6is an exemplary schematic of an operational unit600of the acoustic management module for in-ear canal echo suppression in accordance with an embodiment. The operational unit600may contain more or less than the number of components shown in the schematic. The operational unit600can include an echo suppressor610and a voice decision logic620.

The echo suppressor610can be a Least Mean Squares (LMS) or Normalized Least Mean Squares (NLMS) adaptive filter that models an ear canal transfer function (ECTF) between the ECR125and the ECM123. The echo suppressor610generates the modified electronic signal, e(n), which is provided as an input to the voice decision logic620; e(n) is also termed the error signal e(n) of the echo suppressor610. Briefly, the error signal e(n)412is used to update the filter H(w) to model the ECTF of the echo path. The error signal e(n)412closely approximates the user's spoken voice signal u(n)607when the echo suppressor610accurately models the ECTF.

In the configuration shown the echo suppressor610minimizes the error between the filtered signal, {tilde over (γ)}(n), and the electronic internal signal, z(n), in an effort to obtain a transfer function H′ which is a best approximation to the H(w) (i.e., ECTF). H(w) represents the transfer function of the ear canal and models the echo response. (z(n)=u(n)+y(n)+v(n), where u(n) is the spoken voice607, y(n) is the echo609, and v(n) is background noise (if present, for instance due to improper sealing).)

During operation, the echo suppressor610monitors the mixed signal323delivered to the ECR125and produces an echo estimate {tilde over (γ)}(n) of an echo y(n)609based on the captured electronic internal signal410and the mixed signal323. The echo suppressor610, upon learning the ECTF by an adaptive process, can then suppress the echo y(n)609of the acoustic audio content603(e.g., output mixed signal323) in the electronic internal signal z(n)410. It subtracts the echo estimate Y(n) from the electronic internal signal410to produce the modified electronic internal signal e(n)412.

The voice decision logic620analyzes the modified electronic signal412e(n) and the electronic ambient signal426to produce a voice activity level622, a. The voice activity level a identifies a probability that the user is speaking, for example, when the user is using the earpiece for two way voice communication. The voice activity level622can also indicate a degree of voicing (e.g., periodicity, amplitude), When the user is speaking, voice is captured externally (such as from acoustic ambient signal424) by the ASM111in the ambient environment and also by the ECM123in the ear canal. The voice decision logic provides the voice activity level a to the acoustic management module201as an input parameter for mixing the ASM111and ECM123signals. Briefly referring back toFIG.4, the acoustic management module201performs the mixing as a function of the voice activity level a and the background noise level (see G=f(BNL)+f(VAL)).

For instance, at low background noise levels and low voice activity levels, the acoustic management module201amplifies the electronic ambient signal426from the ASM111relative to the electronic internal signal410from the ECM123in producing the mixed signal323. At medium background noise levels and medium voice activity levels, the acoustic management module201attenuates low frequencies in the electronic ambient signal426and attenuates high frequencies in the electronic internal signal410. At high background noise levels and high voice activity levels, the acoustic management module201amplifies the electronic internal signal410from the ECM123relative to the electronic ambient signal426from the ASM111in producing the mixed signal. The acoustic management module201can additionally apply frequency specific filters based on the characteristics of the background noise.

FIG.7is a schematic of a control unit700for controlling adaptation of a first set (736) and a second set (738) of filter coefficients of the echo suppressor610for in-ear canal echo suppression in accordance with an exemplary embodiment. Briefly, the control unit700illustrates a freezing (fixing) of weights upon detection of spoken voice. The echo suppressor resumes weight adaptation when e(n) is low, and freezes weights when e(n) is high signifying a presence of spoken voice.

When the user is not speaking, the ECR125can pass through ambient sound captured at the ASM111, thereby allowing the user to hear environmental ambient sounds. As previously discussed, the echo suppressor610models an ECTF and suppresses an echo of the mixed signal323that is looped back to the ECR125by way of the ASM111(see dotted line Loop Back path). When the user is not speaking, the echo suppressor continually adapts to model the ECTF. When the ECTF is properly modeled, the echo suppressor610produces a modified internal electronic signal e(n) that is low in amplitude level (i.e., low in error). The echo suppressor adapts the weights to keep the error signal low. When the user speaks, the echo suppressor however initially produces a high-level e(n) (e.g., the error signal increases). This happens since the speaker's voice is uncorrelated with the audio signal played out the ECR125, which disrupts the echo suppressor's ECTF modeling ability.

The control unit700upon detecting a rise in e(n), freezes the weights of the echo suppressor610to produce a fixed filter H′(w) fixed738. Upon detecting the rise in e(n) the control unit adjusts the gain734for the ASM signal and the gain732for the mixed signal323that is looped back to the ECR125. The mixed signal323fed back to the ECR125permits the user to hear themselves speak. Although the weights are frozen when the user is speaking, a second filter H′(w)736continually adapts the weights for generating a second e(n) that is used to determine a presence of spoken voice. That is, the control unit700monitors the second error signal e(n) produced by the second filter736for monitoring a presence of the spoken voice.

The first error signal e(n) (in a parallel path) generated by the first filter738is used as the mixed signal323. The first error signal contains primarily the spoken voice since the ECTF model has been fixed due to the weights. That is, the second (adaptive) filter is used to monitor a presence of spoken voice, and the first (fixed) filter is used to generate the mixed signal323.

Upon detecting a fall of e(n), the control unit restores the gains734and732and unfreezes the weights of the echo suppressor, and the first filter H′(w) returns to being an adaptive filter. The second filter H′(w)736remains on stand-by until spoken voice is detected, and at which point, the first filter H′(w)738goes fixed, and the second filter H′(w)736begins adaptation for producing the e(n) signal that is monitored for voice activity. Notably, the control unit700monitors e(n) from the first filter738or the second filter736for changes in amplitude to determine when spoken voice is detected based on the state of voice activity.

FIG.8is a block diagram800of a method for an audio mixing system to mix an external microphone signal with an internal microphone signal based on a background noise level and voice activity level in accordance with an exemplary embodiment.

As illustrated the mixing circuitry816(shown in center) receives an estimate of the background noise level812for mixing either or both the right earpiece ASM signal802and the left earpiece ASM signal804with the left earpiece ECM signal806. (The right earpiece ECM signal can be used similarly.) An operating mode selection system814selects a switching808(e.g., 2-in, 1-out) between the left earpiece ASM signal804and the right earpiece ASM signal802. As indicated earlier, the ASM signals and ECM signals can be first amplified with a gain system and then filtered with a filter system (the filtering may be accomplished using either analog or digital electronics or both). The audio input signals802,804, and806are therefore taken after this gain and filtering process, if any gain and filtering are used.

The Acoustic Echo Cancellation (AEC) system810can be activated with the operating mode selection system814when the mixed signal audio output828is reproduced with the ECR125in the same ear as the ECM123signal used to create the mixed signal audio output828. The acoustic echo cancellation platform810can also suppress an echo of a spoken voice generated by the wearer of the earpiece100. This ensures against acoustic feedback (“howlback”).

The Voice Activated System (VOX)818in conjunction with a de-bouncing circuit822activates the electronic switch826to control the mixed signal output828from the mixing circuitry816; the mixed signal is a combination of the left ASM signal804or right ASM signal802, with the left ECM806signal. Though not shown, the same arrangement applies for the other earphone device for the right ear, if present. Note that earphones can be used in both ears simultaneously. In a contra-lateral operating mode, as selected by operating mode selection system814, the ASM and ECM signal are taken from opposite earphone devices, and the mix of these signals is reproduced with the ECR in the earphone that is contra-lateral to the ECM signal, and the same as the ASM signal.

For instance, in the contra-lateral operating mode, the ASM signal from the Right earphone device is mixed with the ECM signal from the left earphone device, and the audio signal corresponding to a mix of these two signals is reproduced with the Ear Canal Receiver (ECR) in the Right earphone device. The mixed signal audio output828therefore can contain a mix of the ASM and ECM signals when the user's voice is detected by the VOX. This mixed signal audio output can be used in loopback as a user Self-Monitor System to allow the user to hear their own voice as reproduced with the ECR125, or it may be transmitted to another voice system, such as a mobile phone, walkie-talkie radio etc. The VOX system818that activates the switch826may be one a number of VOX embodiments.

In a particular operating mode, specified by unit814, the conditioned ASM signal is mixed with the conditioned ECM signal with a ratio dependent on the BNL using audio signal mixing circuitry and the method described in eitherFIG.10orFIG.11. As the BNL increases, then the ASM signal is mixed with the ECM signal with a decreasing level. When the BNL is above a particular value, then a minimal level of the ASM signal is mixed with the ECM signal. When the VOX switch618is active, the mixed ASM and ECM signals are then sent to mixed signal output828. The switch de-bouncing circuit826ensures against the VOX818rapidly closing on and off (sometimes called chatter). This can be achieved with a timing circuit using digital or analog electronics. For instance, with a digital system, once the VOX has been activated, a time starts to ensure that the switch826is not closed again within a given time period, e.g. 100 ms. The delay unit824can improve the sound quality of the mixed signal audio output828by compensating for any latency in voice detection by the VOX system818. In some exemplary embodiments, the switch debouncing circuit822can be dependent by the BNL. For instance, when the BNL is high (e.g. above 85 dBA), the de-bouncing circuit can close the switch826sooner after the VOX output818determines that no user speech (e.g. spoken voice) is present.

FIG.9is a block diagram of a method920for calculating background noise levels in accordance with an exemplary embodiment. Briefly, the background noise levels can be calculated according to different contexts, for instance, if the user is talking while audio content is playing, if the user is talking while audio content is not playing, if the user is not talking but audio content is playing, and if the user is not talking and no audio content is playing. For instance, the system takes as its inputs either the ECM and/or ASM signal, depending on the particular system configuration. If the ECM signal is used, then the measured BNL accounts for an acoustic attenuation of the earpiece and a level of reproduced audio content.

As illustrated, modules922-928provide exemplary steps for calculating a base reference background noise level. The ECM or ASM audio input signal922can be buffered923in real-time to estimate signal parameters. An envelope detector924can estimate a temporal envelope of the ASM or ECM signal. A smoothing filter925can minimize abruptions in the temporal envelope. (A smoothing window926can be stored in memory). An optional peak detector927can remove outlier peaks to further smooth the envelope. An averaging system928can then estimate the average background noise level (BNL_1) from the smoothed envelope.

If at step929, it is determined that the signal from the ECM was used to calculate the BNL_1, an audio content level932(ACL) and noise reduction rating933(NRR) can be subtracted from the BNL_1estimate to produce the updated BNL931. This is done to account for the audio content level reproduced by the ECR125that delivers acoustic audio content to the earpiece100, and to account for an acoustic attenuation level (i.e. Noise Reduction Rating933) of the earpiece. For example, if the user is listening to music, the acoustic management module201takes into account the audio content level delivered to the user when measuring the BNL. If the ECM is not used to calculate the BNL at step929, the previous real-time frame estimate of the BNL930is used.

At step936, the acoustic management module201updates the BNL based on the current measured BNL and previous BNL measurements935. For instance, the updated BNL937can be a weighted estimate 934 of previous BNL estimates according to BNL=2*previous BNL+(1−w)*current BNL, where 0<W<1. The BNL can be a slow time weighted average of the level of the ASM and/or ECM signals, and may be weighted using a frequency-weighting system, e.g. to give an A-weighted SPL level.

FIG.10is a block diagram1040for mixing an external microphone signal with an internal microphone signal based on a background noise level to produce a mixed output signal in accordance with an exemplary embodiment. The block diagram can be implemented by the acoustic management module201or the processor121. In particular,FIG.10primarily illustrates the selection of microphone filters based on the background noise level. The microphone filters are used to condition the external and internal microphone signals before mixing.

As shown, the filter selection module1045can select one or more filters to apply to the microphone signals before mixing. For instance, the filter selection module1045can apply an ASM filter1048to the ASM signal1047and an ECM filter1051to the ECM signal1052based on the background noise level1042. The ASM and ECM filters can be retrieved from memory based on the characteristics of the background noise. An operating mode1046can determine whether the ASM and ECM filters are look-up curves1043from memory or filters whose coefficients are determined in real-time based on the background noise levels.

Prior to mixing with summing unit1049to produce output signal1050, the ASM signal1047is filtered with ASM filter1048, and the ECM signal1052is filtered with ECM filter1051. The filtering can be accomplished by a time-domain transversal filter (FIR-type filter), an IIR-type filter, or with frequency-domain multiplication. The filter can be adaptive (i.e. time variant), and the filter coefficients can be updated on a frame-by-frame basis depending on the BNL. The filter coefficients for a particular BNL can be loaded from computer memory using pre-defined filter curves1043, or can be calculated using a predefined algorithm1044, or using a combination of both (e.g. using an interpolation algorithm to create a filter curve for both the ASM filter1048and ECM filter1051from predefined filters).

FIG.11is a block diagram for an analog circuit for mixing an external microphone signal with an internal microphone signal based on a background noise level in accordance with an exemplary embodiment.

In particular,FIG.11shows a method1160for the filtering of the ECM and ASM signals using analog electronic circuitry prior to mixing. The analog circuit can process both the ECM and ASM signals in parallel; that is, the analog components apply to both the ECM and ASM signals. In one exemplary embodiment, the input audio signal1161(e.g., ECM signal, ASM signal) is first filtered with a fixed filter1162. The filter response of the fixed filter1162approximates a low-pass shelf filter when the input signal1161is an ECM signal, and approximates a high-pass filter when the input signal1161is an ASM signal. In an alternate exemplary embodiment, the filter1162is a unity-pass filter (i.e. no spectral attenuation) and the gain units G1, G2etc instead represent different analog filters. As illustrated, the gains are fixed, though they may be adapted in other embodiments. Depending on the BNL1169, the filtered signal is then subjected to one of three gains; G11163, G21164, or G31165. (The analog circuit can include more or less than the number of gains shown.)

For low BNLs (e.g. when BNL<L1170, where L1is a predetermined level threshold1171), a G1is determined for both the ECM signal and the ASM signal. The gain G1for the ECM signal is approximately zero; i.e. no ECM signal would be present in the output signal1175. For the ASM input signal, G1would be approximately unity for low BNL.

For medium BNLs (e.g. when BNL<L21172, where L2is a predetermined level threshold1173), a G2is determined for both the ECM signal and the ASM signal. The gain G2for the ECM signal and the ASM signal is approximately the same. In another embodiment, the gain G2can be frequency dependent so as to emphasize low frequency content in the ECM and emphasize high frequency content in the ASM signal in the mix. For high BNL; G31165is high for the ECM signal, and low for the ASM signal. The switches1166,1167, and1168ensure that only one gain channel is applied to the ECM signal and ASM signal. The gain scaled ASM signal and ECM signal are then summed at junction1174to produce the mixed output signal1175.

Examples of filter response curves for three different BNL are shown inFIG.12, which is a table illustrating exemplary filters suitable for use with an Ambient Sound Microphone (ASM) and Ear Canal Microphone (ECM) based on measured background noise levels (BNL).

The basic trend for the ASM and ECM filter response at different BNLs is that at low BNLs (e.g. <60 dBA), the ASM signal is primarily used for voice communication. At medium BNL; ASM and ECM are mixed in a ratio depending on the BNL, though the ASM filter can attenuate low frequencies of the ASM signal, and attenuate high frequencies of the ECM signal. At high BNL (e.g. >85 dB), the ASM filter attenuates most al the low frequencies of the ASM signal, and the ECM filter attenuates most all the high frequencies of the ECM signal. In another embodiment of the Acoustic Management System, the ASM and ECM filters may be adjusted by the spectral profile of the background noise measurement. For instance, if there is a large Low Frequency noise in the ambient sound field of the user, then the ASM filter can reduce the low-frequencies of the ASM signal accordingly, and boost the low-frequencies of the ECM signal using the ECM filter.

Where applicable, the present embodiments of the invention can be realized in hardware, software or a combination of hardware and software. Any kind of computer system or other apparatus adapted for carrying out the methods described herein are suitable. A typical combination of hardware and software can be a mobile communications device with a computer program that, when being loaded and executed, can control the mobile communications device such that it carries out the methods described herein. Portions of the present method and system may also be embedded in a computer program product, which comprises all the features enabling the implementation of the methods described herein and which when loaded in a computer system, is able to carry out these methods.

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. 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.