Patent Description:
<CIT> relates to a method of processing an audio signal in a portable listening device, the audio signal comprising a low frequency part having an LF-bandwidth and a high-frequency part having a HF bandwidth.

Murakami et al. : "SPEECH ENHANCEMENT BASED ON A COMBINED HIGHER FREQUENCY REGENERATION TECHNIQUE AND RBF NETWORKS",.

<NPL>, relates to a method for noise reduction in speech signals, wherein the nonlinear spectral subtraction (NSS) method is applied to the down-sampled noisy speech signal. Further, the method restores the missing higher frequency components from the narrow bandwidth enhanced speech signal.

The present invention provides a method with features of independent claim <NUM> and an ear-wearable electronic device with features of independent claim <NUM>. The dependent claims depict other embodiments of the invention. This application relates generally to ear-level electronic systems and devices, including hearing aids, personal amplification devices, and hearables. In one embodiment, an ear-worn electronic device is configured to be worn in, on or about an ear of a wearer. The ear-worn electronic device includes at least one microphone configured to convert sound that includes speech to an electrical signal. The device includes a loudspeaker/receiver, an analog to digital converter that converts the electrical signal to a digitized signal, and a processor operably coupled to the microphone, the loudspeaker, and the analog to digital converter. The processor is operable to apply a low-pass filter to the digitized signal to remove a high-frequency component and obtain a low-frequency component. The processor applies speech enhancement to the low-frequency component and applies blind bandwidth extension to the enhanced low-frequency component to recover or synthesize an estimate of at least part of the high frequency component. The processor outputs an enhanced speech signal via the loudspeaker/receiver that is a combination of the enhanced low-frequency component and the bandwidth-extended high frequency component, wherein a cutoff frequency of the low-pass filter is updated during use of the ear-wearable device, wherein the cutoff frequency is updated based on a change in signal quality estimates for frequency bands below the cutoff frequency, and wherein the signal quality estimates comprise at least one of a posteriori signal-to-noise-ratio (SNR) and a coherent-to-diffuse power ratio (CDR).

The above summary is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The figures and the detailed description below more particularly exemplify illustrative embodiments.

The discussion below makes reference to the following figures.

Embodiments disclosed herein are directed to speech enhancement in an ear-worn or ear-level electronic device. Such a device may include cochlear implants and bone conduction devices, without departing from the scope of this disclosure. The devices depicted in the figures are intended to demonstrate the subject matter, but not in a limited, exhaustive, or exclusive sense. Ear-worn electronic devices (also referred to herein as "hearing devices"), such as hearables (e.g., wearable earphones, ear monitors, and earbuds), hearing aids, hearing instruments, and hearing assistance devices, typically include an enclosure, such as a housing or shell, within which internal components are disposed.

Typical components of a hearing device can include a processor (e.g., a digital signal processor or DSP), memory circuitry, power management and charging circuitry, one or more communication devices (e.g., one or more radios, a near-field magnetic induction (NFMI) device), one or more antennas, one or more microphones, buttons and/or switches, and a receiver/speaker, for example. Hearing devices can incorporate a long-range communication device, such as a Bluetooth® transceiver or other type of radio frequency (RF) transceiver.

The term hearing device of the present disclosure refers to a wide variety of ear-level electronic devices that can aid a person with impaired hearing. The term hearing device also refers to a wide variety of devices that can produce processed sound for persons with normal hearing. Hearing devices include, but are not limited to, behind-the-ear (BTE), in-the-ear (ITE), in-the-canal (ITC), invisible-in-canal (IIC), receiver-in-canal (RIC), receiver-in-the-ear (RITE) or completely-in-the-canal (CIC) type hearing devices or some combination of the above. Throughout this disclosure, reference is made to a "hearing device," which is understood to refer to a system comprising a single left ear device, a single right ear device, or a combination of a left ear device and a right ear device.

Speech enhancement (SE) is an audio signal processing technique that aims to improve the quality and intelligibility of speech signals corrupted by noise. Due to its application in several areas such as automatic speech recognition (ASR), mobile communication, hearing aids, etc., several methods have been proposed for SE over the years. Recently, the success of deep neural networks (DNNs) in automatic speech recognition led to investigation of DNNs for noise suppression for ASR and speech enhancement. Generally, corruption of speech by noise is a complex process and a complex non-linear model like DNN is well suited for modeling it.

Although it has shown promising results and can outperform classical SE methods, the DNN-based speech enhancement system complexity and processing delay typically leads to a less feasible real-time architecture with high latency and computational cost, especially for highly constrained hearing aids. For example, a prototype DNN-based real-time speech enhancement system with a neural network containing three hidden layers (<NUM> neurons for each of the layer) with four look-back frames, leads to approximately <NUM> processing delay. In contrast, the processing delay for a currently used fast-acting single microphone noise reduction (FSMNR) speech enhancement only takes <NUM>.

Generally, noisy speech in the real-world has frequency dependent signal-to-noise-ratio (SNR). For example, speech signals may exhibit higher SNR in low bands due to the main presence of speech (e.g., <NUM>-<NUM>) and lower SNR in high bands (beyond <NUM>). Because of lower SNR at high bands, higher risk of corrupting speech (e.g., distortion) is presented when attempting to remove noise. Moreover, total complexity of low band plus high band speech enhancement, especially DNN-based speech enhancement, can be significantly more costly than the low band enhancement only.

In this disclosure, various embodiments utilize speech enhancement schemes that perform speech processing on low band signals to reduce complexity of the speech enhancement algorithm. This reduced bandwidth speech enhancement is combined with blind bandwidth extension (BWE) processing to recover or synthesize high frequency bands from the speech-enhanced spectrum components at low frequency bands. Generally, BWE analyzes a narrowband signal to which a (typically) high frequency cutoff has been applied. Based on the speech-enhanced narrowband signal, the BWE algorithm predicts high frequency components which are then added to the signal thereby extending the spectrum of the signal. This is in contrast to other bandwidth extension schemes, which may explicitly encode details of the high frequency components in the narrowband signal for later decoding and extension.

Note that in the present disclosure, the terms "low band," "narrowband," "high band," "wideband," are not intended to imply specific frequency limits, but are used to indicate relative bandwidth in different stages of a signal processing stream. For example, a source signal may be passed through a low-pass filter to produce a narrowband signal that has lower bandwidth (e.g., smaller range between low and high frequencies present in the signal) than the source signal, but does not necessarily conform to established definitions of narrowband that may be commonly used in various audio signal technologies.

Using narrowband signals for speech detection/enhancement can reduce the complexity of advanced enhancement schemes (e.g., DNN-based speech enhancement) by computing enhancement only in the low frequency bands, which may require fewer bins or lower model order. The BWE is applied to the speech-enhanced signal, which improves the quality of the speech signal that is ultimately output by a loudspeaker/receiver of an ear-wearable device.

In <FIG>, a flowchart shows a high-level representation of a speech enhancement process according to an example embodiment. An input signal <NUM> is provided by a transducer such as a microphone. The input signal <NUM> may be digitized via an analog-to-digital converter (ADC) for subsequent digital signal processing. The input signal <NUM> passes through a low-pass filter <NUM> which removes high-frequency components from the signal. The cutoff frequency for the filter <NUM> may be set within a range acceptable for speech processing. For example, traditional narrowband telephone speech is typically limited to around <NUM>, and so the cutoff frequency could be set at or near <NUM>. As will be described in greater detail below, the cutoff frequency can optionally be adapted during use, e.g., to account for changes in environmental noise.

The low-pass filter <NUM> outputs a band-limited signal <NUM> that includes speech plus noise that is processed via a speech enhancement module <NUM>. Generally, the speech enhancement module identifies components of the signal that correspond to speech and may, for example, increase the amplitude of the speech components relative to everything else in the signal <NUM>, the latter which could include ambient noise, electrical noise, etc. Because the speech enhancement module <NUM> operates on a reduced bandwidth signal, it can have lower complexity than a larger bandwidth speech enhancer. Thus, a bandwidth limited speech enhancement module <NUM> can be more readily implemented in a resource-limited device such as a hearing aid.

The result of processing by the speech enhancement module is an enhanced signal <NUM> in which speech can be heard more clearly over background noise and other nonspeech components. The enhanced signal <NUM> is still bandwidth limited, however, and therefore may be missing some high frequency components of the speech. This reduction in bandwidth may result, for example, in unvoiced/fricative sounds being muted or inaudible.

In order to produce an output signal in which speech is more easily understood, the enhanced speech signal <NUM> is input to a bandwidth extender <NUM> that recovers and/or synthesizes high frequency content in the signal to create an increased bandwidth output signal <NUM>. The increased bandwidth output signal <NUM> has an increase at least in high frequency portions of the speech signal, e.g., spectral bands above the cutoff frequency utilized by the low-pass filter <NUM>.

In <FIG>, a block diagram illustrates a more detailed signal processing path according to an example embodiment. A noisy input signal <NUM> is digitized (not shown) and input to a windowing function <NUM> which assembles consecutive samples into a window, where part of each window may overlap with previous windows. The samples in each window are transformed into the frequency domain via a fast Fourier transform (FFT) <NUM>.

A posteriori SNR analysis 203a provides an estimate of signal quality for a selected range of frequencies. The posteriori SNR analysis 203a can be used to select a cutoff frequency f_cutoff used by a low-pass filter <NUM>. This allows changing f_cutoff based on current noise characteristics of the input signal <NUM>. Note that the use of the posteriori SNR analysis 203a for f_cutoff is optional, and f_cutoff can be a pre-set fixed value, and/or a userconfigurable fixed value, e.g., based on a user-selected setting from a control application.

The posteriori SNR is one signal quality estimate that can be used to reevaluate f_cutoff. In another embodiment, a coherent-to-diffuse power ratio (CDR) 203b can be used instead of or in addition to the posteriori SNR analysis 203a for determining f_cutoff. The CDR analysis 203ba is a sub-band analysis that assists in clarifying speech in highly reverberant environments. The CDR analysis 203b can be used to generate an input for DNN-based dereverberation. If DNN-based noise reduction and dereverberation are implemented simultaneously, a combination of the outputs of posteriori SNR analysis 203a and CDR analysis 203b can be used to determine the f_cutoff.

After the noisy input signal has been windowed and transformed into frequency domain, the low-pass cutoff filter <NUM> generally separates high and low frequency components used in subsequent stages of the speech enhancement processing. One reason to separate the high-band from the low-band is that noisy speech in real-world has frequencydependent SNR, e.g., higher SNR in low bands due to the main presence of speech and lower SNR in high bands. Because of lower SNR at high bands, there higher risk of damaging speech (e.g., introducing distortion) when attempting to remove noise on the wideband signal. Therefore, using the narrowband, lower frequency signal for speech enhancement reduces risk of creating distortion when conducting speech enhancement. Also, as noted above, use of the lower frequency band can reduce computational complexity of the speech enhancement algorithm, which can be useful in low power devices.

After filter, the low-band portion of the signal is processed via an advanced speech enhancement (ASE) processor <NUM>. The ASE processor <NUM> may be, in one embodiment, a DNN-based speech enhancer including noise reduction and dereverberation. Other machine learning algorithms may be used instead of or together with DNN-based speech enhancement, such as convolutional neural networks (SNN), recurrent neural networks (RNN), etc..

In parallel with the ASE processor <NUM>, a linear predictive coding (LPC) analysis <NUM> is conducted on the low-pass signal, which is converted back to the time domain by an inverse FFT (IFFT) <NUM>. The LPC analysis <NUM> derives LPC coefficients <NUM> and LPC analysis filter <NUM> based on the narrow-band, noisy spectral envelope. The LPC coefficients <NUM> can be derived using auto-correlation method and are served as the inputs for spectral envelope extension <NUM>. The spectral envelope extension <NUM> generally involves a identifying feature sets in the signal and mapping technique between narrow-band and wideband feature sets. Relevant methods for spectral envelope extension include linear mapping based on codebooks, Bayesian estimation methods and DNN-based mapping. In some embodiments, a subset of the LPC coefficient <NUM> can selected for use by the spectral envelope extension based on a level of hearing loss of a user of the hearing assistance device. For example, if the user cannot hear frequencies higher than fh, then LPC coefficients affecting frequencies above fh may be omitted from the spectral envelope extension <NUM>.

The LPC analysis filter <NUM> is used for predicting the enhanced low-frequency excitation signal, which will serve as the input for excitation signal extension <NUM> for high frequency ranges. Generally, speech can be broken up into two parts: the excitation and the spectral envelope. In order to attain high quality wideband speech, both parts are typically extended. When considering a speech input signal that is band-limited, the assumption of the excitation being spectrally flat only holds for unvoiced frames. For voiced frames, the excitation signal includes of impulsive components placed at pitch harmonics. Therefore, the speech signal is first broken up into frames and classified as voiced and unvoiced frames via spectral flatness measure. Then different modulation strategies apply for unvoiced and voiced frames. For the excitation signal extension <NUM>, spectral modulation methods may be used, including spectral band replication and spectral folding.

Similar to the excitation extension <NUM>, in order to isolate the spectral envelope, spectral envelope extension <NUM> extrapolates the narrowband spectral envelope to that of the reconstructed wideband speech spectral envelope. This problem generally involves finding the right feature set and the right mapping technique between narrowband and wideband feature sets.

In reference again to the ASE processor <NUM>, a spectral smoothing process <NUM> may be applied to the enhanced spectrum components at low frequency ranges that are output from the ASE processor <NUM>. The spectral smoothing <NUM> is optional, and may deploy a moving window in the frequency domain in order to address spectrum discontinuity. The output of the spectral smoothing is inverse-transformed to the time domain via IFFT <NUM>. As indicated by convolution block <NUM>, the output of the IFFT <NUM> is filtered with the with LPC analysis filter <NUM> to get the excitation signal <NUM> based on the narrow-band enhanced signal. After the excitation signal extension <NUM>, the wideband speech signal <NUM> is obtained by convolving <NUM> the wideband enhanced excitation signal <NUM> with the wideband LPC feature coefficients <NUM> (which are the output of spectral envelope extension <NUM>).

As noted above, the cutoff frequency (f_cutoff) of the low-pass filter <NUM> defines what information in the input signal <NUM> is used for ASE processing <NUM> and which information is discarded. In some embodiments, the cutoff frequency may be actively adjusted during use by monitoring the active posteriori-SNR estimates. These estimates determine a cut-off frequency where signal components higher than the cut-off frequency have a high risk of creating distortion when conducting speech enhancement.

In <FIG>, a plot shows how posteriori-SNR estimates may be used to select cutoff frequencies according to an example embodiment. In this plot, each of the bars represent the estimated posteriori-SNR for one of the analyzed bands. An SNR threshold <NUM> may be decided empirically (e.g., -6dB) and a cutoff frequency <NUM> may be selected that ensures frequency bands below the cutoff frequency <NUM> have an average SNR that is below SNR threshold <NUM>.

In <FIG>, a flowchart shows an example of how f_cutoff may be actively adjusted according to an example embodiment. The procedure involves initializing <NUM> the cut-off frequency. For example, f_cutoff could be initially set to <NUM>, which is an approximate upper limit on narrowband telephonic speech. The rest of the procedure evaluates conditions which might justify changing f_cutoff. There may be some practical limits on how much f_cutoff should change from this value, e.g., no less than about <NUM> and no more than about <NUM>. For example, there may be unacceptable loss of speech information if components below the lower limit are filtered. As to the higher limit, there may be reduced benefits in the ASE model processing frequencies that extend past the higher limit, as well as there possibly being excessive noise or less useful speech components above the higher limit.

At block <NUM>, which represents the entry point of an infinite loop, the average of posteriori-SNR estimates for frequency bands that are below the current cut-off frequency are calculated. This calculation is used to determine whether to set a new cutoff frequency as shown in blocks <NUM>-<NUM>, which will be described in greater detail below. Setting a new cutoff frequency may have impacts in downstream processes in the signal path, and so block <NUM> is used to limit the frequency of cut-off frequency updates.

Note that, in reference again to <FIG>, the ASE processor <NUM> may include a machine learning model trained on spectra defined by a specific f_cutoff of the low pass filter <NUM>. Therefore, a change in f_cutoff may involve making changes to the ASE processor <NUM> (see block <NUM> in <FIG>), such as using a different set of weights and biases applied to a neural network, using a different network structure, etc. Such changes to the ASE processor <NUM> may be computationally expensive and may have other side effects, e.g., introducing unwanted artifacts into the audio stream. As a result, if f_cutoff is changeable during use, the system may introduce some checks to ensure that f_cutoff does not change too frequently.

In the example shown in <FIG>, the decision block <NUM> checks whether the last change to f_cutoff occurred greater than a minimum elapsed time t_min. If so, then a new f_cutoff can be calculated and used as shown in subsequent blocks. Note that the use of elapsed time is only one example of how to limit "churning" of f_cutoff. In other examples, a running average of the posteriori-SNR estimates calculated at block <NUM> could be used to determine whether changes to the noise profile is shorter term or longer term, and this could be used with or without elapsed time checks. Also note that the elapsed time could be checked elsewhere in the program loop. For example, after a change in f_cutoff, the calculation of SNR at block <NUM> could be suspended until at least time t_min has elapsed.

Once sufficient time has passed (and/or other criteria are satisfied) and block <NUM> returns 'yes,' a decision whether to change f_cutoff begins at block <NUM>. At block <NUM>, it is determined whether the average of posteriori-SNR estimates determined at block <NUM> is greater than or equal to the predetermined SNR threshold (e.g., -<NUM> dB). This indicates that additional high frequency information may be incorporated into the signal processing. If block <NUM> returns 'yes,' a new, higher, f_cutoff may be determined and updated as shown in the following blocks <NUM>-<NUM>.

Blocks <NUM>-<NUM> detail how a new f_cutoff can be calculated. Generally, this involves iteratively calculating <NUM> the average posteriori SNR by individually adding the sub-band posteriori-SNR estimates beyond f_cutoff into consideration until the average of posteriori-SNR estimates is smaller than the SNR threshold. The value of f_cutoff is updated <NUM> with the center frequency of the lastly added sub-band in block <NUM>, which would generally correspond to the highest frequencies of the newly considered sub-bands.

If it is determined at block <NUM> that the average of posteriori-SNR estimates is smaller than the predetermined SNR threshold (block <NUM> returns 'no'), a second check may be made as shown at block <NUM> to see of the average SNR estimate is smaller than a second threshold (e.g., -9dB). If not, then the average of posteriori-SNR estimate is within an acceptable range and f_cutoff remains the same as shown in block <NUM>. If block <NUM> returns 'yes," then the average SNR estimate may be too low, and as shown in block <NUM>, the average SNR is recalculated by removing high frequency sub-bands until the SNR estimate is less than the second threshold. At block <NUM>, f_cutoff is updated with the center frequency of the highest remaining sub-band. In the alternate, instead of performing the calculation in block <NUM> if block <NUM> returns 'yes,' block <NUM> could involve reverting the value of f_cutoff to the initial value set in block <NUM>. If f_cutoff is changed at blocks <NUM> or <NUM>, this may also require updating <NUM> the ASE model based on the new f_cutoff. Other system components may also be changed in response to a change in f_cutoff, such as the LPC analyzer <NUM> shown in <FIG>.

In <FIG>, a flowchart shows an example of how f_cutoff may be actively adjusted based on CDR according to another example embodiment. The procedure could be implemented separately or together with the procedure in <FIG>. In the latter case, some operations may be merged, such as initializing <NUM>, <NUM> the cut-off frequency, determining elapsed time (or other condition) since last update of f_cutoff <NUM>, <NUM>, and updating <NUM>, <NUM> the ASE model with a new f_cutoff.

At block <NUM>, which represents the entry point of an infinite loop, the average of CDR estimates for frequency bands that are below the current cut-off frequency are calculated. The decision block <NUM> checks whether the last change to f_cutoff occurred greater than a minimum elapsed time t_min, or some other criteria is described as in relation to <FIG>. Once sufficient time has passed (and/or other criteria are satisfied) and block <NUM> returns 'yes,' a decision whether to change f_cutoff begins at block <NUM>. At block <NUM>, it is determined whether the average of CDR estimates determined at block <NUM> is greater than or equal to the predetermined CDR threshold. This indicates that additional high frequency information may be incorporated into the signal processing. If block <NUM> returns 'yes,' a new, higher, f_cutoff may be determined and updated as shown in the following blocks <NUM>-<NUM>.

Blocks <NUM>-<NUM> detail how a new f_cutoff can be calculated. Generally, this involves iteratively calculating <NUM> the average CDR by individually adding the sub-band CDR estimates beyond f_cutoff into consideration until the average of CDR estimates is smaller than the CDR threshold. The value of f_cutoff is updated <NUM> with the center frequency of the lastly added sub-band in block <NUM>, which would generally correspond to the highest frequencies of the newly considered sub-bands.

If it is determined at block <NUM> that the average of CDR estimates is smaller than the predetermined CDR threshold (block <NUM> returns 'no'), a second check may be made as shown at block <NUM> to see of the average CDR estimate is smaller than a second threshold. If not, then the average of CDR estimate is within an acceptable range and f_cutoff remains the same as shown in block <NUM>. If block <NUM> returns "yes," then the average CDR estimate may be too low, and as shown in block <NUM>, the average CDR is recalculated by removing high frequency sub-bands until the CDR estimate is less than the second threshold. At block <NUM>, f_cutoff is updated with the center frequency of the highest remaining sub-band. In the alternate, instead of performing the calculation in block <NUM> if block <NUM> returns 'yes,' block <NUM> could involve reverting the value of f_cutoff to the initial value set in block <NUM>. If f_cutoff is changed at blocks <NUM> or <NUM>, this may also require updating <NUM> the ASE model based on the new f_cutoff. Other system components may also be changed in response to a change in f_cutoff, such as the LPC analyzer <NUM> shown in <FIG>.

In summary, a speech enhancement scheme utilizes advanced speech enhancement processing for low frequency bands and BWE for high frequency bands. The bandwidth extension scheme provides improved speech enhancement or de-noising tool in the high frequency bands. Using just the low frequency bands for speech enhancement reduces the complexity of advanced enhancement schemes. An optional adaptive scheme can actively adjust the cut-off frequency that separates the high and low frequency bands based on the estimate of posteriori SNR and/or CDR (which are typically calculated in classic speech enhancement schemes). These implementations can be used in any ear-worn electronic device, such as a hearing aid.

In <FIG>, a block diagram illustrates an ear-worn electronic device <NUM> in accordance with any of the embodiments disclosed herein. The hearing device <NUM> includes a housing <NUM> configured to be worn in, on, or about an ear of a wearer. The hearing device <NUM> shown in <FIG> can represent a single hearing device configured for monaural or singleear operation or one of a pair of hearing devices configured for binaural or dual-ear operation. The hearing device <NUM> shown in <FIG> includes a housing <NUM> within or on which various components are situated or supported. The housing <NUM> can be configured for deployment on a wearer's ear (e.g., a behind-the-ear device housing), within an ear canal of the wearer's ear (e.g., an in-the-ear, in-the-canal, invisible-in-canal, or completely-in-the-canal device housing) or both on and in a wearer's ear (e.g., a receiver-in-canal or receiver-in-the-ear device housing).

The hearing device <NUM> includes a processor <NUM> operatively coupled to a main memory <NUM> and a non-volatile memory <NUM>. The processor <NUM> can be implemented as one or more of a multi-core processor, a digital signal processor (DSP), a microprocessor, a programmable controller, a general-purpose computer, a special-purpose computer, a hardware controller, a software controller, a combined hardware and software device, such as a programmable logic controller, and a programmable logic device (e.g., FPGA, ASIC). The processor <NUM> can include or be operatively coupled to main memory <NUM>, such as RAM (e.g., DRAM, SRAM). The processor <NUM> can include or be operatively coupled to non-volatile memory <NUM>, such as ROM, EPROM, EEPROM or flash memory. As will be described in detail hereinbelow, the non-volatile memory <NUM> is configured to store instructions that facilitate ASE on a low-band signal and BWE to recover/synthesize high frequencies for audio reproduction.

The hearing device <NUM> includes an audio processing facility operably coupled to, or incorporating, the processor <NUM>. The audio processing facility includes audio signal processing circuitry (e.g., analog front-end, analog-to-digital converter, digital-to-analog converter, DSP, and various analog and digital filters), a microphone arrangement <NUM>, and a speaker or receiver <NUM>. The microphone arrangement <NUM> can include one or more discrete microphones or a microphone array(s) (e.g., configured for microphone array beamforming). Each of the microphones of the microphone arrangement <NUM> can be situated at different locations of the housing <NUM>. It is understood that the term microphone used herein can refer to a single microphone or multiple microphones unless specified otherwise.

The hearing device <NUM> may also include a user interface with a user-actuatable control <NUM> operatively coupled to the processor <NUM>. The user-actuatable control <NUM> is configured to receive an input from the wearer of the hearing device <NUM>. The input from the wearer can be any type of user input, such as a touch input, a gesture input, or a voice input. The user-actuatable control <NUM> may be configured to receive an input from the wearer of the hearing device <NUM> to change speech enhancement parameters of the hearing device <NUM>, such as enabling/disabling of speech enhancement, fixed or adaptable cutoff frequency, etc. Other parameters, such as upper and lower bounds the adaptable cutoff frequency may be set by a user or technician, e.g., to adapt performance to suit the level of hearing impairment of the user of the device.

The hearing device <NUM> also includes a speech enhancement module <NUM> operably coupled to the processor <NUM>. The speech enhancement module <NUM> can be implemented in software, hardware, or a combination of hardware and software. The speech enhancement module <NUM> can be a component of, or integral to, the processor <NUM> or another processor (e.g., a DSP) coupled to the processor <NUM>. The speech enhancement module <NUM> is configured to detect speech in different types of acoustic environments. The different types of sound can include speech, music, and several different types of noise (e.g., wind, transportation noise and vehicles, machinery), etc., and combinations of these and other sounds (e.g., transportation noise with speech).

According to various embodiments, the speech enhancement module <NUM> can be configured to filter out audio signals above a cutoff frequency such that only a lower frequency component of the audio signals is subject to speech enhancement via a machine learning algorithm. Such machine learning enhancement may be performed, for example, via a DNN, CNN, RNN, etc. Generally, these neural networks are trained to detect speech patterns in the presence of noise, and can be used to improve the detectability of the speech by a listener through isolation and amplification of the speech patterns and/or attenuation of the noise.

The hearing device <NUM> can include one or more communication devices <NUM> coupled to one or more antenna arrangements. For example, the one or more communication devices <NUM> can include one or more radios that conform to an IEEE <NUM> (e.g., WiFi®) or Bluetooth® (e.g., BLE, Bluetooth® <NUM>. <NUM>, <NUM>, <NUM>, <NUM> or later) specification, for example. In addition, or alternatively, the hearing device <NUM> can include a near-field magnetic induction (NFMI) sensor (e.g., an NFMI transceiver coupled to a magnetic antenna) for effecting shortrange communications (e.g., ear-to-ear communications, ear-to-kiosk communications).

The hearing device <NUM> also includes a power source, which can be a conventional battery, a rechargeable battery (e.g., a lithium-ion battery), or a power source comprising a supercapacitor. In the embodiment shown in <FIG>, the hearing device <NUM> includes a rechargeable power source <NUM> which is operably coupled to power management circuitry for supplying power to various components of the hearing device <NUM>. The rechargeable power source <NUM> is coupled to charging circuity <NUM>. The charging circuitry <NUM> is electrically coupled to charging contacts on the housing <NUM> which are configured to electrically couple to corresponding charging contacts of a charging unit when the hearing device <NUM> is placed in the charging unit.

Although reference is made herein to the accompanying set of drawings that form part of this disclosure, one of at least ordinary skill in the art will appreciate that various adaptations and modifications of the embodiments described herein are within, or do not depart from, the scope of this disclosure. Therefore, it is to be understood that, within the scope of the appended claims, the claimed invention may be practiced other than as explicitly described herein.

The terms "coupled" or "connected" refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements). Either term may be modified by "operatively" and "operably," which may be used interchangeably, to describe that the coupling or connection is configured to allow the components to interact to carry out at least some functionality (for example, a radio chip may be operably coupled to an antenna element to provide a radio frequency electric signal for wireless communication).

Terms related to orientation, such as "top," "bottom," "side," and "end," are used to describe relative positions of components and are not meant to limit the orientation of the embodiments contemplated. For example, an embodiment described as having a "top" and "bottom" also encompasses embodiments thereof rotated in various directions unless the content clearly dictates otherwise.

Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude other embodiments from the scope of the disclosure.

As used herein, "have," "having," "include," "including," "comprise," "comprising" or the like are used in their open-ended sense, and generally mean "including, but not limited to. " It will be understood that "consisting essentially of," "consisting of," and the like are subsumed in "comprising," and the like. The term "and/or" means one or all of the listed elements or a combination of at least two of the listed elements.

Claim 1:
A method comprising:
receiving (<NUM>) a digitized signal that includes speech;
applying (<NUM>) a low-pass filter to the digitized signal to remove a high-frequency component and obtain a low-frequency component;
applying (<NUM>) speech enhancement to the low-frequency component;
applying (<NUM>) blind bandwidth extension to the enhanced low-frequency component to obtain a bandwidth-extended high frequency component that is an estimate of the high frequency component; and
outputting (<NUM>), to a loudspeaker of an ear-wearable device (<NUM>), an enhanced speech signal that is a combination of the enhanced low-frequency component and the bandwidth-extended high frequency component,
wherein a cutoff frequency of the low-pass filter is updated during use of the ear-wearable device (<NUM>),
wherein the cutoff frequency is updated based on a change in signal quality estimates for frequency bands below the cutoff frequency, and
wherein the signal quality estimates comprise at least one of a posteriori signal-to-noise-ratio (SNR) and a coherent-to-diffuse power ratio (CDR).