Method and device for voice operated control

[0001] This Application is a Continuation in Part application of application Ser. No. 12/102,555, filed 14 Apr. 2008, which claims the priority benefit of Provisional Application No. 60/911,691 filed on Apr. 13, 2007, the entire disclosures of which are incorporated herein by reference.

[0002] The present invention pertains to sound processing using earpieces, and more particularly, to a device and method for controlling operation of an earpiece based on voice activity.

[0003] It can be difficult to communicate using an earpiece or earphone device in the presence of high-level background sounds. The earpiece microphone can pick up environmental sounds such as traffic, construction, and nearby conversations that can degrade the quality of the communication experience. In the presence of babble noise, where numerous talkers are simultaneously speaking, the earpiece does not adequately discriminate between voices in the background and the voice of the user operating the earpiece.

[0004] Although audio processing technologies can adequately suppress noise, the earpiece is generally sound agnostic and cannot differentiate sounds. Thus, a user desiring to speak into the earpiece may be competing with other people's voices in his or her proximity that are also captured by the microphone of the earpiece.

[0005] A need therefore exists for a method and device of personalized voice operated control.

[0006] Embodiments in accordance with the present invention provide a method and device for voice operated control.

[0007] In a first embodiment, an earpiece can include an Ambient Sound Microphone (ASM) configured to capture ambient sound, an Ear Canal Microphone (ECM) configured to capture internal sound in an ear canal, and a processor operatively coupled to the ASM and the ECM. The processor can detect a spoken voice generated by a wearer of the earpiece based on an analysis of the ambient sound measured at the ASM and the internal sound measured at the ECM.

[0008] A voice operated control (VOX) operatively coupled to the processor can control a mixing of the ambient sound and the internal sound for producing a mixed signal. The VOX can control at least one among a voice monitoring system, a voice dictation system, and a voice recognition system. The VOX can manage a delivery of the mixed signal based on one or more aspects of the spoken voice, such as a volume level, a voicing level, and a spectral shape of the spoken voice. The VOX can further control a second mixing of the audio content and the mixed signal delivered to the ECR. A transceiver operatively coupled to the processor can transmit the mixed signal to at least one among a cell phone, a media player, a portable computing device, and a personal digital assistant.

[0009] In a second embodiment, an earpiece can include an Ambient Sound Microphone (ASM) configured to capture ambient sound, an Ear Canal Microphone (ECM) configured to capture internal sound in an ear canal, an Ear Canal Receiver (ECR) operatively coupled to the processor and configured to deliver audio content to the ear canal, and a processor operatively coupled to the ASM, the ECM and the ECR. The processor can detect a spoken voice generated by a wearer of the earpiece based on an analysis of the ambient sound measured at the ASM and the internal sound measured at the ECM.

[0010] A voice operated control (VOX) operatively coupled to the processor can mix the ambient sound and the internal sound to produce a mixed signal. The VOX can control the mix based on one or more aspects of the audio content and the spoken voice, such as a volume level, a voicing level, and a spectral shape of the spoken voice. The one or more aspects of the audio content can include at least one among a spectral distribution, a duration, and a volume of the audio content. The audio content can be provided via a phone call, a voice message, a music signal, an alarm or an auditory warning. The VOX can include a level detector for comparing a sound pressure level (SPL) of the ambient sound and the internal sound, a correlation unit for assessing a correlation of the ambient sound and the internal sound for detecting the spoken voice, a coherence unit for determining whether the spoken voice originates from the wearer, or a spectral analysis unit for detecting whether spectral portions of the spoken voice are similar in the ambient sound and the internal sound.

[0011] In a third embodiment, a dual earpiece can include a first earpiece and a second earpiece. The first earpiece can include a first Ambient Sound Microphone (ASM) configured to capture a first ambient sound, and a first Ear Canal Microphone (ECM) configured to capture a first internal sound in an ear canal. The second earpiece can include a second Ambient Sound Microphone (ASM) configured to capture a second ambient sound, a second Ear Canal Microphone (ECM) configured to capture a second internal sound in an ear canal, and a processor operatively coupled to the first earpiece and the second earpiece. The processor can detect a spoken voice generated by a wearer of the earpiece based on an analysis of at least one of the first and second ambient sound and at least one of the first and second internal sound. A voice operated control (VOX) operatively coupled to the processor, the first earpiece, and the second earpiece, can control a mixing of at least one of the first and second ambient sound and at least one of the first and second internal sound for producing a mixed signal.

[0012] The dual earpiece can further include a first Ear Canal Receiver (ECR) in the first earpiece for receiving audio content from an audio interface, and a second ECR in the second earpiece for receiving the audio content. The VOX can control a second mixing of the mixed signal with the audio content to produce a second mixed signal and control a delivery of the second mixed signal to the first ECR and the second ECR. For instance, the VOX can receive the first ambient sound from the first earpiece and the second internal sound from the second earpiece for controlling the mixing.

[0013] In a fourth embodiment, a method for voice operable control suitable for use with an earpiece can include the steps of measuring an ambient sound received from at least one Ambient Sound Microphone (ASM), measuring an internal sound received from at least one Ear Canal Microphone (ECM), detecting a spoken voice from a wearer of the earpiece based on an analysis of the ambient sound and the internal sound, and controlling at least one voice operation of the earpiece if the presence of spoken voice is detected. The analysis can be non-difference comparison such as a correlation, a coherence, cross-correlation, or a signal ratio. For example in at least one exemplary embodiment the ratio of a measured first and second sound signal can be used to determine the presence of a user's voice. For example if a ratio of first signal/second signal or vice versa is above or below a set value, for example if an ECM measures a second signal at 90 dB and an ASM measures a first signal at 80 dB, then the ratio 90 dB/80 dB>1 would be indicative of a user generated sound (e.g., voice). At least one exemplary embodiment could also use the log of the ratio or a difference of the logs. In one arrangement, the step of detecting a spoken voice is performed only if an absolute sound pressure level of the ambient sound or the internal sound is above a predetermined threshold. The method can further include performing a level comparison analysis of a first ambient sound captured from a first ASM in a first earpiece and a second ambient sound captured from a second ASM in a second earpiece. In another configuration, the level comparison analysis can be between a first internal sound captured from a first ECM in a first earpiece and a second internal sound captured from a second ECM in a second earpiece.

[0014] In a fifth embodiment, a method for voice operable control suitable for use with an earpiece can include measuring an ambient sound received from at least one Ambient Sound Microphone (ASM), measuring an internal sound received from at least one Ear Canal Microphone (ECM), performing a cross correlation between the ambient sound and the internal sound, declaring a presence of spoken voice from a wearer of the earpiece if a peak of the cross correlation is within a predetermined amplitude range and a timing of the peak is within a predetermined time range, and controlling at least one voice operation of the earpiece if the presence of spoken voice is detected. For instance, the voice operated control can manage a voice monitoring system, a voice dictation system, or a voice recognition system. The spoken voice can be declared if the peak and the timing of the cross correlation reveals that the spoken voice arrives at the at least one ECM before the at least one ASM.

[0015] In one configuration, the cross correlation can be performed between a first ambient sound within a first earpiece and a first internal sound within the first earpiece. In another configuration, the cross correlation can be performed between a first ambient sound within a first earpiece and a second internal sound within a second earpiece. In yet another configuration, the cross correlation can be performed either between a first ambient sound within a first earpiece and a second ambient sound within a second earpiece, or between a first internal sound within a first earpiece and a second internal sound within a second earpiece.

[0025] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] 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.

[0030] At least one exemplary embodiment of the invention is directed to an earpiece for voice operated control. Reference is made to FIG. 1 in which an earpiece device, generally indicated as earpiece 100, is constructed and operates in accordance with at least one exemplary embodiment of the invention. As illustrated, earpiece 100 depicts an electro-acoustical assembly 113 for an in-the-ear acoustic assembly, as it would typically be placed in the ear canal 131 of a user 135. The earpiece 100 can be an in the ear earpiece, behind the ear earpiece, receiver in the ear, open-fit device, or any other suitable earpiece type. The earpiece 100 can be partially or fully occluded in the ear canal, and is suitable for use with users having healthy or abnormal auditory functioning.

[0031] Earpiece 100 includes an Ambient Sound Microphone (ASM) 111 to capture ambient sound, an Ear Canal Receiver (ECR) 125 to deliver audio to an ear canal 131, and an Ear Canal Microphone (ECM) 123 to assess a sound exposure level within the ear canal. The earpiece 100 can partially or fully occlude the ear canal 131 to provide various degrees of acoustic isolation. The assembly is designed to be inserted into the user's ear canal 131, and to form an acoustic seal with the walls 129 of the ear canal at a location 127 between the entrance 117 to the ear canal 131 and the tympanic membrane (or ear drum) 133. Such a seal is typically achieved by means of a soft and compliant housing of assembly 113. Such a seal can create a closed cavity 131 of approximately 5 cc between the in-ear assembly 113 and the tympanic membrane 133. As a result of this seal, the ECR (speaker) 125 is able 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 133 resulting from the sound field at the entrance to the ear canal 131. This seal is also a basis for a sound isolating performance of the electro-acoustic assembly.

[0032] Located adjacent to the ECR 125, is the ECM 123, which is acoustically coupled to the (closed or partially closed) ear canal cavity 131. One of its functions is that of measuring the sound pressure level in the ear canal cavity 131 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 100. In one arrangement, the ASM 111 is housed in the assembly 113 to monitor sound pressure at the entrance to the occluded or partially occluded ear canal 131. All transducers shown can receive or transmit audio signals to a processor 121 that undertakes audio signal processing and provides a transceiver for audio via the wired or wireless communication path 119.

[0033] The earpiece 100 can actively monitor a sound pressure level both inside and outside an ear canal 131 and enhance spatial and timbral sound quality while maintaining supervision to ensure safe sound reproduction levels. The earpiece 100 in 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).

[0034] The earpiece 100 can generate an Ear Canal Transfer Function (ECTF) to model the ear canal 131 using ECR 125 and ECM 123, as well as an Outer Ear Canal Transfer function (OETF) using ASM 111. For instance, the ECR 125 can deliver an impulse within the ear canal 131 and generate the ECTF via cross correlation of the impulse with the impulse response of the ear canal 131. The earpiece 100 can 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 earpiece 100 to safely administer and monitor sound exposure to the ear.

[0035] Referring to FIG. 2, a block diagram 200 of the earpiece 100 in accordance with an exemplary embodiment is shown. As illustrated, the earpiece 100 can include the processor 121 operatively coupled to the ASM 111, ECR 125, and ECM 123 via one or more Analog to Digital Converters (ADC) 202 and Digital to Analog Converters (DAC) 203. The processor 121 can utilize computing technologies such as a microprocessor, Application Specific Integrated Chip (ASIC), and/or digital signal processor (DSP) with associated storage memory 208 such as Flash, ROM, RAM, SRAM, DRAM or other like technologies for controlling operations of the earpiece device 100. The processor 121 can also include a clock to record a time stamp.

[0036] As illustrated, the earpiece 100 can include a voice operated control (VOX) module 201 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 201 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 201 can be a hardware component implemented by discrete or analog electronic components or a software component. In one arrangement, the processor 121 can provide functionality of the VOX 201 by way of software, such as program code, assembly language, or machine language.

[0037] The memory 208 can also store program instructions for execution on the processor 121 as well as captured audio processing data. For instance, memory 208 can be off-chip and external to the processor 121, 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. 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 processor 121 to provide high speed data access. The storage memory 208 can be non-volatile memory such as SRAM to store captured or compressed audio data.

[0038] The earpiece 100 can include an audio interface 212 operatively coupled to the processor 121 and VOX 201 to receive audio content, for example from a media player, cell phone, or any other communication device, and deliver the audio content to the processor 121. The processor 121 responsive to detecting voice operated events from the VOX 202 can adjust the audio content delivered to the ear canal. For instance, the processor 121 (or VOX 201) can lower a volume of the audio content responsive to detecting an event for transmitting the acute sound to the ear canal. The processor 121 by way of the ECM 123 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 201.

[0039] The earpiece 100 can further include a transceiver 204 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 204 can also provide support for dynamic downloading over-the-air to the earpiece 100. It should be noted also that next generation access technologies can also be applied to the present disclosure.

[0040] The location receiver 232 can 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 earpiece 100.

[0041] The power supply 210 can utilize common power management technologies such as replaceable batteries, supply regulation technologies, and charging system technologies for supplying energy to the components of the earpiece 100 and to facilitate portable applications. A motor (not shown) can be a single supply motor driver coupled to the power supply 210 to improve sensory input via haptic vibration. As an example, the processor 121 can direct the motor to vibrate responsive to an action, such as a detection of a warning sound or an incoming voice call.

[0042] The earpiece 100 can 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 earpiece 100 can be reused in different form factors for the master and slave devices.

[0043] FIG. 3 is a flowchart of a method 300 for voice operated control in accordance with an exemplary embodiment. The method 300 can be practiced with more or less than the number of steps shown and is not limited to the order shown. To describe the method 300, reference will be made to FIG. 4 and components of FIG. 1 and FIG. 2, although it is understood that the method 300 can be implemented in any other manner using other suitable components. The method 300 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device.

[0044] The method 300 can start in a state wherein the earpiece 100 has been inserted in an ear canal 131 of a wearer. As shown in step 302, the earpiece 100 can measure ambient sounds in the environment received at the ASM 111. 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.

[0045] During the measuring of ambient sounds in the environment, the earpiece 100 also measures internal sounds, such as ear canal levels, via the ECM 123 as shown in step 304. The internal sounds can include ambient sounds passing through the earpiece 100 as well as spoken voice generated by a wearer of the earpiece 100. Although the earpiece 100 when inserted in the ear can partially of fully occlude the ear canal 131, the earpiece 100 may not completely attenuate the ambient sound. The passive aspect of the earpiece 100, due to the mechanical and sealing properties, can provide upwards of a 22 dB noise reduction. Portions of ambient sounds higher than the noise reduction level may still pass through the earpiece 100 into the ear canal 131 thereby producing residual sounds. For instance, high energy low frequency sounds may not be completely attenuated. Accordingly, residual sound may be resident in the ear canal 131 producing internal sounds that can be measured by the ECM 123. Internal sounds can also correspond to audio content and spoken voice when the user is speaking and/or audio content is delivered by the ECR 125 to the ear canal 131 by way of the audio interface 212.

[0046] At step 306, the processor 121 compares the ambient sound and the internal sound to determine if the wearer (i.e., the user 135 wearing the earpiece 100) of the earpiece 100 is speaking. That is, the processor 121 determines if the sound received at the ASM 111 and ECM 123 corresponds to the wearer's voice or to other voices in the wearer's environment. Notably, the enclosed air chamber (˜5 cc volume) within the user's ear canal 131 due to the occlusion of the earpiece 100 causes a build up of sound waves when the wearer speaks. Accordingly, the ECM 123 picks up the wearer's voice in the ear canal 131 when the wearer is speaking even though the ear canal is occluded. The processor 121, by way of one or more non-difference comparison approaches, such as correlation analysis, cross-correlation analysis, and coherence analysis determines whether the sound captured at the ASM 111 and ECM 123 corresponds to the wearer's voice or ambient sounds in the environment, such as other users talking in a conversation. The processor 121 can also identify a voicing level from the ambient sound and the internal sound. The voicing level identifies a degree of intensity and periodicity of the sound. For instance, a vowel is highly voiced due to the periodic vibrations of the vocal cords and the intensity of the air rushing through the vocal cords from the lungs. In contrast, unvoiced sounds such as fricatives and plosives have a low voicing level since they are produced by rushing non-periodic air waves and are relatively short in duration.

[0047] If at step 308, spoken voice from the wearer of the earpiece 100 is detected, the earpiece 100 can proceed to control a mixing of the ambient sound received at the ASM 111 with the internal sound received at the ECM 123, as shown in step 310, and in accordance with the block diagram 400 of FIG. 4. If spoken voice from the wearer is not detected, the method 300 can proceed back to step 302 and step 304 to monitor ambient and internal sounds. The VOX 201 can also generate a voice activity flag declaring the presence of spoken voice by the wearer of the earpiece 100, which can be passed to other subsystems.

[0048] As shown in FIG. 4, the first mixing 402 can include adjusting the gain of the ambient sound and internal sound, and with respect to background noise levels. For instance, the VOX 201 upon deciding that the sound captured at the ASM 111 and ECM 123 originates from the wearer of the earpiece 100 can combine the ambient sound and the internal sound with different gains to produce a mixed signal. The mixed signal can apply weightings more towards the ambient sound or internal sound depending on the background noise level, the wearer's vocalization level, or spectral characteristics. The mixed signal can thus include sound waves from the wearer's voice captured at the ASM 111 and also sound waves captured internally in the wearer's ear canal generated via bone conduction.

[0049] Briefly referring to FIG. 4, a block diagram 400 for voice operated control is shown. The VOX 201 can include algorithmic modules 402 for a non-difference comparison such as correlation, cross-correlation, and coherence. The VOX 201 applies one or more of these decisional approaches, as will be further described ahead, for determining if the ambient sound and internal sound correspond to the wearer's spoken voice. In the decisional process, the VOX 201 can prior to the first mixing 404 assign mixing gains (α) and (1−α) to the ambient sound signal from the ASM 111 and the internal sound signal from the ECM 123. These mixing gains establish how the ambient sound signals and internal sound signals are combined for further processing.

[0050] In one arrangement based on correlation, the processor 121 determines if the internal sound captured at the ECM 123 arrives before the ambient sound at the ASM 111. Since the wearer's voice is generated via bone conduction in the ear canal 131, it travels a shorter distance than an acoustic wave emanating from the wearer's mouth to the ASM 111 at the wearer's ear. The VOX 201 can analyze the timing of one or more peaks in a cross correlation between the ambient sound and the internal sound to determine whether the sound originates from the ear canal 131, thus indicating that the wearer's spoken voice generated the sound. Whereas, sounds generated external to the ear canal 131, such as those of neighboring talkers, reach the ASM 111 before passing through the earpiece 100 into the wearer's ear canal 131. A spectral comparison of the ambient sound and internal sound can also be performed to determine the origination point of the captured sound.

[0051] In another arrangement based on level detection, the processor 121 determines if either the ambient sound or internal sound exceeds a predetermined threshold, and if so, compares a Sound Pressure Level (SPL) between the ambient sound and internal sound to determine if the sound originates from the wearer's voice. In general, the SPL at the ECM 123 is higher than the SPL at the ASM 111 if the wearer of the earpiece 100 is speaking. Accordingly, a first metric in determining whether the sound captured at the ASM 111 and ECM 123 is to compare the SPL levels at both microphones.

[0052] In another arrangement based on spectral distribution, a spectrum analysis can be performed on audio frames to assess the voicing level. The spectrum analysis can reveal peaks and valleys of vowels characteristic of voiced sounds. Most vowels are represented by three to four formants which contain a significant portion of the audio energy. Formants are due to the shaping of the air passageway (e.g., throat, tongue, and mouth) as the user ‘forms’ speech sounds. The voicing level can be assigned based on the degree of formant peaking and bandwidth.

[0053] The threshold metric can be first employed so as to minimize the amount of processing required to continually monitor sounds in the wearer's environment before performing the comparison. The threshold establishes the level at which a comparison between the ambient sound and internal sound is performed. The threshold can also be established via learning principles, for example, wherein the earpiece 100 learns when the wearer is speaking and his or her speaking level in various noisy environments. For instance, the processor 121 can record background noise estimates from the ASM 111 while simultaneously monitoring the wearer's speaking level at the ECM 123 to establish the wearer's degree of vocalization relative to the background noise.

[0054] Returning back to FIG. 3, at step 312, the VOX 201 can deliver the mixed signal to a portable communication device, such as a cell phone, personal digital assistant, voice recorder, laptop, or any other networked or non-networked system component (see also FIG. 4). Recall the VOX 201 can generate the mixed signal in view of environmental conditions, such as the level of background noise. So, in high background noises, the mixed signal can include more of the internal sound from the wearer's voice generated in ear canal 131 and captured at the ECM 123 than the ambient sound with the high background noise. In a quiet environment, the mixed signal can include more of the ambient sound captured at the ASM 111 than the wearer's voice generated in ear canal 131. The VOX 201 can also apply various spectral equalizations to account for the differences in spectral timbre from the ambient sound and the internal sound based on the voice activity level and/or mixing scheme.

[0055] As shown in optional step 314, the VOX 201 can also record the mixed signal for further analysis by a voice processing system. For instance, the earpiece 100 having identified voice activity levels previously at step 308 can pass a command to another module such as a voice recognition system, a voice dictation system, a voice recorder, or any other voice processing module. The recording of the mixed signal at step 314 allows the processor 121, or voice processing system receiving the mixed signal to analyze the mixed signal for information, such as voice commands or background noises. The voice processing system can thus examine a history of the mixed signal from the recorded information.

[0056] The earpiece 100 can also determine whether the sound corresponds to a spoken voice of the wearer even when the wearer is listening to music, engaged in a phone call, or receiving audio via other means. Moreover, the earpiece 100 can adjust the internal sound generated within the ear canal 131 to account for the audio content being played to the wearer while the wearer is speaking. As shown in step 316, the VOX 201 can determine if audio content is being delivered to the ECR 125 in making the determination of spoken voice. Recall, audio content such as music is delivered to the ear canal 131 via the ECR 125 which plays the audio content to the wearer of the earpiece 100. If at step 318, the earpiece 100 is delivering audio content to the user, the VOX 201 at step 320 can control a second mixing of the mixed signal with the audio content to produce a second mixed signal (see second mixer 406 of FIG. 4). This second mixing provides loop-back from the ASM 111 and the ECM 123 of the wearer's own voice to allow the wearer to hear themselves when speaking in the presence of audio content delivered to the ear canal 131 via the ECR 125. If audio content is not playing, the method 300 can proceed back to step 310 to control the mixing of the wearer's voice (i.e., speaker voice) between the ASM 111 and the ECM 123.

[0057] Upon mixing the mixed signal with the audio content, the VOX 201 can deliver the second mixed signal to the ECR 125 as indicated in step 322 (see also FIG. 4). In such regard, the VOX 201 permits the wearer to monitor his or her own voice and simultaneously hear the audio content. The method can end after step 322. Notably, the second mixing can also include soft muting of the audio content during the duration of voice activity detection, and resuming audio content playing during non-voice activity or after a predetermined amount of time. The VOX 201 can further amplify or attenuate the spoken voice based on the level of the audio content if the wearer is speaking at a higher level and trying to overcome the audio content they hear. For instance, the VOX 201 can compare and adjust a level of the spoken voice with respect to a previously calculated (e.g., via learning) level.

[0058] FIG. 5 is a flowchart 500 for a voice activated switch based on level differences in accordance with an exemplary embodiment. The flowchart 500 can include more or less than the number of steps shown and is not limited to the order of the steps. The flowchart 500 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device.

[0059] FIG. 5 illustrates an arrangement wherein the VOX 201 uses as its inputs the ambient sound microphone (ASM) signals from the left (L) 578 and right (R) 582 earphone devices, and the Ear Canal Microphone (ECM) signals from the left (L) 580 and right (R) 584 signals. The ASM and ECM signals are amplified with amplifiers 575, 577, 579, 581 before being filtered using Band Pass Filters (BPFs) 583, 585, 587, 589, which can have the same frequency response. The filtering can use analog or digital electronics, as may the subsequent signal strength comparator 588 of the filtered and amplified ASM and ECM signals from the left and right earphone devices. The VOX 201 determines that when the filtered ECM signal level exceeds the filtered ASM signal level by an amount determined by the reference difference unit 586, decision units 590, 591 deem that user-generated voice is present. The VOX 201 introduces a further decision unit 592 that takes as its input the outputs of decision units 590, 591 from both the left and right earphone devices, which can be combined into a single functional unit. As an example, the decision unit 592 can be either an AND or OR logic gate, depending on the operating mode selected with (optional) user-input 598. The output decision 594 operates the VOX 201 in a voice communication system, for example, allowing the user's voice to be transmitted to a remote individual (e.g. using radio frequency communications) or for the user's voice to be recorded.

[0060] FIG. 6 is a block diagram 600 of a voice activated switch using inputs from level and cross correlation in accordance with an exemplary embodiment. The block diagram 600 can include more or less than the number of steps shown and is not limited to the order of the steps. The block diagram 600 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device.

[0061] As illustrated, the voice activated switch 600 uses both the level-based detection method 670 described in FIG. 5 and also a correlation-based method 672 described ahead in FIG. 7. The decision unit 699 can be either an AND or OR logic gate, depending on the operating mode selected with (optional) user-input 698. The decision unit 699 can generate a voice activated on or off decision 691.

[0062] FIG. 7 is a flowchart 700 for a voice activated switch based on cross correlation in accordance with an exemplary embodiment. The flowchart 700 can include more or less than the number of steps shown and is not limited to the order of the steps. The flowchart 700 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device.

[0063] A cross-correlation between two signals is a measure of their similarity. In general, a cross-correlation between ASM and ECM signals is defined according to the following equation:

[0064] $\begin{array}{cc}X\mathrm{Corr}\left(n,1\right)=\sum _{n=0}^N\mathrm{ASM}\left(n\right)\mathrm{ECM}\left(n-1\right),\mathrm{Where}\text{:}l=0,1,2,\dots N& \left(1\right)\end{array}$

[0065] Where: ASM(n) is the n^th sample of the ASM signal, and ECM(n−1) is the (n−1)^th sample of the ECM signal.

[0066] Using a non-difference comparison approach such as cross-correlation (or correlation and coherence) between the ASM and ECM signals to determine user voice activity is more reliable than taking the level difference of the ASM and ECM signals. Using the cross-correlation rather than a level differencing approach significantly reduces “False-positives” which may 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 (i.e. and a higher ECM signal level) than on the outside of the same ear canal (i.e. and a lower ASM signal level). Therefore, a VOX system that relies on level difference between the ASM and the ECM is often “tricked” into falsely determining that user voice was present.

[0067] False-positive speech detection can use unnecessary radio bandwidth for single-duplex voice communication systems. Furthermore, false positive user voice activity can be dangerous, for instance with an emergency worker in the field whose incoming voice signal from a remote location may be muted in response to a false-positive VOX decision. Thus, minimizing false positives using a non-difference comparison approach is beneficial to protecting the user from harm.

[0068] Single-lag auto-correlation is sufficient when only a single audio signal is available for analysis, but can provide false-positives both when the input signal is from an ECM (for instance, voice sounds such as murmurs or humming will trigger the VOX), or when the input signal is from an ASM (in such a case, voice sounds from ambient sound sources such as other individuals or reproduced sound from loudspeakers will trigger the VOX).

[0069] Like Correlation and Cross-Correlation, a coherence function is also a measure of similarity between two signals and is a non-difference comparison approach, defined as:

[0070] $\begin{array}{cc}{\gamma }_{\mathrm{xy}}^2=\frac{{G_{\mathrm{xy}}\left(f\right)}^2}{G_{\mathrm{xx}}\left(f\right)G_{\mathrm{yy}}\left(f\right)}& \left(2\right)\end{array}$
Where G_xy 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 (1), applying a window function (e.g. Hanning window), and transforming the result to the frequency domain (e.g. via an FFT). G_xx or G_yy is the auto-power spectrum of either the ASM or ECM signals, and can be calculated by first computing the auto-correlation (using equation 1, but where the two input signals are both from either the ASM or ECM and transforming the result to the frequency domain. The coherence function gives a frequency-dependant 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 only analyze those speech frequencies in the ASM and ECM signals (e.g. in the 300 Hz-3 kHz range), whereby a high coherence indicates voice activity (e.g. a coherence greater than 0.7).

[0071] As illustrated, there are two parallel paths for the left and right earphone devices. For each earphone device, the inputs are the filtered ASM and ECM signals. In the first path, the left (L) ASM signal 788 is passed to a gain function 775 and band-pass filtered by BPF 783. The left (L) ECM signal 780 is also passed to a gain function 777 and band-pass filtered by BPF 785. In the second path, the right (R) ASM signal 782 is passed to a gain function 779 and band-pass filtered by BPF 787. The right (R) ECM signal 784 is also passed to a gain function 781 and band-pass filtered by BPF 789. The filtering can be performed in the time domain or digitally using frequency or time domain filtering. A cross correlation or coherence between the gain scaled and band-pass filtered signals is then calculated at unit 795.

[0072] Upon calculating the cross correlation, decision unit 796 undertakes analysis of the cross-correlation vector to determine a peak and the lag at which this peak occurs for each path. An optional “learn mode” unit 799 is used to train the decision unit 796 to be robust to detect the user voice, and lessen the chance of false positives (i.e. predicting user voice when there is none) and false negatives (i.e. predicting no user voice when there is user voice). In this learn mode, the user is prompted to speak (e.g. using a user-activated voice or non-voice audio command and/or visual command using a display interface on a remote control unit), and the VOX 201 records the calculated cross-correlation and extracts the peak value and lag at which this peak occurs. The lag and (optionally) peak value for this reference measurement in “learn mode” is then recorded to computer memory and is used to compare other cross-correlation measurements. If the lag-time for the peak cross-correlation measurement matches the reference lag value, or another pre-determined value, then the decision unit 796 outputs a “user voice active” message (e.g. represented by a logical 1, or soft decision between 0 and 1) to the second decision unit 720. In some embodiments, the decision unit 720 can be an OR gate or AND gate; as determined by the particular operating mode 722 (which may be user defined or pre-defined). The decision unit 720 can generate a voice activated on or off decision 724.

[0073] FIG. 8 is a flowchart 800 for a voice activated switch based on cross correlation using a fixed delay method in accordance with an exemplary embodiment. The flowchart 800 can include more or less than the number of steps shown and is not limited to the order of the steps. The flowchart 800 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device

[0074] Flowchart 800 provides an overview of a multi-band analysis of cross-correlation platform. In one arrangement, the cross-correlation can use a fixed-delay cross-correlation method. The logic output of the different band-pass filters (810-816) are fed into decision unit 896 for both the left earphone device (via band-pass filters 810, 812) and the right earphone device (via band-pass filters 814, 816). The decision unit 896 can be a simple logical AND unit, or an OR unit (this is because depending on the particular vocalization of the user, e.g. a sibilant fricative or a voiced vowel, the lag of the peak in the cross-correlation analysis may be different for different frequencies). The particular configuration of the decision unit 896 can be configured by the operating mode 822, which may be user-defined or pre-defined. The dual decision unit 820 in the preferred embodiment is a logical AND gate, though may be an OR gate, and returns a binary decision to the VOX on or off decision 824.

[0075] FIG. 9 is a flowchart 900 for a voice activated switch based on cross correlation and coherence analysis using inputs from different earpieces in accordance with an exemplary embodiment. The flowchart 900 can include more or less than the number of steps shown and is not limited to the order of the steps. The flowchart 900 can be implemented in a single earpiece, a pair of earpieces, headphones, or other suitable headset audio delivery device.

[0076] Flowchart 900 is a variation of flowchart 700 where instead of comparing the ASM and ECM signals of the same earphone device, the ASM signals of different earphone devices are compared, and alternatively or additionally, the ECM signals of different earphone devices are also compared. As illustrated, there are two parallel paths for the left and right earphone device. For each earphone device, the inputs are the filtered ASM and ECM signals. In the first path, the left (L) ASM signal 988 is passed to a gain function 975 and band-pass filtered by BPF 983. The right (R) ASM signal 980 is also passed to a gain function 977 and band-pass filtered by BPF 985. The filtering can be performed in the time domain or digitally using frequency or time domain filtering. In the second path, the left (L) ECM signal 982 is passed to a gain function 979 and band-pass filtered by BPF 987. The right (R) ECM signal 984 is also passed to a gain function 981 and band-pass filtered by BPF 989.

[0077] A cross correlation or coherence between the gain scaled and band-pass filtered signals is then calculated at unit 996 for each path. Upon calculating the cross correlation, decision unit 996 undertakes analysis of the cross-correlation vector to determine a peak and the lag at which this peak occurs. The decision unit 996 searches for a high coherence or a correlation with a maxima at lag zero to indicate that the origin of the sound source is equidistant to the input sound sensors. If the lag-time for the peak a cross-correlation measurement matches a reference lag value, or another pre-determined value, then the decision unit 996 outputs a “user voice active” message (e.g. represented by a logical 1, or soft decision between 0 and 1) to the second decision unit 920. In some embodiments, the decision unit 920 can be an OR gate or AND gate; as determined by the particular operating mode 922 (which may be user defined or pre-defined). The decision unit 920 can generate a voice activated on or off decision 924. An optional “learn mode” unit 999 is used to train decision units 996, similar to learn mode unit 799 described above with respect to FIG. 7.

[0078] 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.