Abstract: A physiological signal processing system for a physiological waveform that includes a cardiovascular signal component provides a variable high pass filter that is responsive to the physiological waveform, and that is configured to high pass filter the physiological waveform in response to a corner frequency that is applied. A heart rate metric extractor is responsive to the variable high pass filter and is configured to extract a heart rate metric from the physiological waveform that is high pass filtered. A corner frequency adjuster is responsive to the heart rate metric extractor and is configured to determine the corner frequency that is applied to the variable high pass filter, based on the heart rate metric that was extracted. Analogous methods may also be provided.

Abstract: Apparatus and methods for attenuating environmental interference are described. A wearable monitoring apparatus includes a housing configured to be attached to the body of a subject and a sensor module that includes an energy emitter that directs energy at a target region of the subject, a detector that detects an energy response signal—or physiological condition—from the subject, a filter that removes time-varying environmental interference from the energy response signal, and at least one processor that controls operations of the energy emitter, detector, and filter.

Abstract: Volume control circuits for use in electronic devices are provided. Some embodiments of the present invention provide volume control circuits for use in electronic devices. The volume control circuits include a gain circuit, a limiter circuit, a power measurement circuit and a gain adjustment circuit. The gain circuit is configured to receive an input audio signal and amplify the input audio signal based on a gain. The limiter circuit is configured to limit the amplified input audio signal based on a peak safety limit and output an output audio signal having a peak value based on the peak safety limit. The power measurement circuit is configured to measure a power level of the output audio signal. The power level has an associated power safety limit. The gain adjustment circuit is configured to adjust the gain of the gain circuit responsive to the measured power. Related methods and electronic devices are also provided herein.

Abstract: A flat-panel speaker is attached to an exterior surface of a printed circuit board (PCB) housed within a consumer electronic device. Rather than place the flat-panel speaker within a sealed speaker box and then attach the speaker box to the PCB, as is conventional, the present invention attaches the flat-panel speaker to the exterior surface of the PCB without the speaker box. Removing the speaker box allows designers to reduce the dimensions of the device, and to minimize the complexity of the device.

Abstract: An electronic device includes first and second speakers, a microphone, and circuitry configured to generate first and second audio signals in response to a source audio signal, to play the first audio signal over the first speaker, and to play the second audio signal over the second speaker. The first and second audio signals are configured, and the first and second speakers are positioned, so that the first audio signal output by the first speaker and the second audio signal output by the second speaker combine destructively at the microphone.

Abstract: A method and apparatus provide multichannel signal limiting to prevent any channel signal within a multichannel signal from exceeding defined limits, while still preserving the gain and/or amplitude relationships among the individual channel signals. A limiter is configured to calculate a limiting factor as the value needed to prevent a limit violation on the worst-case one of the channel signals, and then commonly apply that limiting factor to the gain control of all channel signals. Thus, the limiter may generate an actual gain value for each channel signal as the product of that channel signal's desired gain value and the current value of the limiting factor. Notably, in multichannel audio signal applications, coordinating gain control across the individual audio channels by use of the commonly applied limiting factor prevents undesirable spatial shifting of the soundstage, e.g., shifting of the stereo image.

Abstract: Portable electronic devices are provided including a housing and first and second audio transducers positioned in the housing. The first and second audio transducers are supported by the housing and driven out of phase relative to one another to provide a leak tolerant output from the portable electronic device. Related earspeakers and methods of operating portable electronic devices are also provided.

Abstract: Crosstalk cancellation systems for left and right channel stereo audio signals that are played over left and right stereo loudspeakers include circuitry that is configured to apply more crosstalk cancellation delay to a difference signal between the left and right stereo audio signals, than to a sum signal of the left and right channel stereo signals. The circuitry may be configured to apply no crosstalk cancellation delay to the sum signal. Related crosstalk cancellation methods and electronic devices incorporating same are also disclosed.

Abstract: A flat-panel speaker is attached to an exterior surface of a printed circuit board (PCB) housed within a consumer electronic device. Rather than place the flat-panel speaker within a sealed speaker box and then attach the speaker box to the PCB, as is conventional, the present invention attaches the flat-panel speaker to the exterior surface of the PCB without the speaker box. Removing the speaker box allows designers to reduce the dimensions of the device, and to minimize the complexity of the device.

Abstract: A clamshell-type wireless communication device has a flip, a base, and a hinge that pivotably connects the flip to the base. The flip pivots relative to the base between an open position and a closed position. An earpiece speaker in the flip renders the voice of a remote party to a user when the flip is in the open position. A loudspeaker within the hinge also renders audible sound to the user. The loudspeaker is positioned within the hinge such that neither the flip nor the base obstructs the audible sound projected by the loudspeaker regardless of whether the flip is in the open position or the closed position.

Abstract: An electronic device includes first and second speakers, a microphone, and circuitry configured to generate first and second audio signals in response to a source audio signal, to play the first audio signal over the first speaker, and to play the second audio signal over the second speaker. The first and second audio signals are configured, and the first and second speakers are positioned, so that the first audio signal output by the first speaker and the second audio signal output by the second speaker combine destructively at the microphone.

Abstract: Volume control circuits for use in electronic devices are provided. Some embodiments of the present invention provide volume control circuits for use in electronic devices. The volume control circuits include a gain circuit, a limiter circuit, a power measurement circuit and a gain adjustment circuit. The gain circuit is configured to receive an input audio signal and amplify the input audio signal based on a gain. The limiter circuit is configured to limit the amplified input audio signal based on a peak safety limit and output an output audio signal having a peak value based on the peak safety limit. The power measurement circuit is configured to measure a power level of the output audio signal. The power level has an associated power safety limit. The gain adjustment circuit is configured to adjust the gain of the gain circuit responsive to the measured power. Related methods and electronic devices are also provided herein.

Abstract: A method and apparatus for limiting an audio signal by establishing a maximum magnitude level that is responsive to a volume control and limiting a reproduced sound to that maximum allowable magnitude level. Limiting circuitry may include analog and digital solutions and may be executed through soft-limiting, hard-limiting, or a combination thereof. A limiter may include circuitry to dynamically detect peak levels in an audio signal. A desired gain may be associated with the audio signal and, if applied, produces a desired peak. This desired peak may be compared to the maximum magnitude level, which may be set relative to a peak acoustic capacity. Audio signal amplification may be set in response to this comparison, such as scaling gain by a ratio of desired peak to maximum magnitude level.

Abstract: A ringback detector determines whether ringback by comparing measurements of a characteristic of the received signal, such as the energy of the received signal, to a threshold. The threshold is set initially to a low value and then updated based on the measurements of received signal. The measurements are then compared to the threshold to determine whether ringback is present. An output signal indicative of ringback is generated when ringback is present.

Abstract: An echo canceler and method for a communications system include an echo-containing signal input for receiving a signal and an echo-causing signal source for developing an echo-causing signal. A first filter coupled to the echo-containing signal input and the echo-causing signal source filters the echo-containing signal over a predetermined time period using an existing filter coefficient set to provide a first echo-canceled output signal at a first filter output mode. A trial filter is coupled to the echo-containing signal input and the echo-causing signal source for processing the echo-containing signal over a predetermined time period using a trial filter coefficient set to provide a trial echo-cancel output signal at the trial filter output mode.

Abstract: Methods and apparatus for echo and noise cancelation contemplate occasional saturation of an echo and/or noise containing source signal and control adaptation of a cancelation filter to minimize the detrimental effects of such source signal saturation. According to exemplary embodiments, filter coefficients of an adaptive filter are updated only when a prevailing value of the source signal is within a predetermined range of possible source signal values. Consequently, the filter response is not perturbed by source signal saturation, and the adaptive filter continues to provide quality echo suppression even immediately following periods of saturation.

Abstract: A method of compressing an audio signal can include accepting input samples of the audio signal wherein the input samples include non-zero input samples. A logarithm of each of the non-zero input samples of the audio signal can be calculated. Compressed output samples for each non-zero input sample can then be determined based on the logarithm of each respective non-zero input sample. Preferably, a linear relationship may exist between logarithms of the non-zero input samples and logarithms of the corresponding compressed output samples. A logarithm of each compressed output sample, corresponding to a non-zero input sample, may be based on a product of a logarithm of each corresponding non-zero input sample and a compression factor. Related devices and computer program products are also discussed.

Abstract: An echo suppressor for bi-directional communications includes an echo canceler and a residual echo suppressor having variable gain. The gain of the residual echo suppressor is controlled based on a characteristic, such as the estimated energy, of the residual voice echo, or alternatively the entire residual echo, preferably on a per-frame basis. In some embodiments, the residual voice echo energy is compared against the estimated non-echo energy to determine the required amount of gain to apply so as to attenuate the residual voice echo below a psychoacoustic perception level. In some optional embodiments, comfort noise is added to the output signal after the residual echo suppressor in an amount that corresponds to the amount of signal energy loss through the residual echo suppressor. Thus, in some embodiments, desired voice and background noise (including local background noise and comfort noise) are used to mask the presence of residual echo.

Abstract: The Least Mean Square (LMS) and Normalized LMS (NLMS) algorithms commonly employed in adaptive filters of echo cancelers are further optimized. Finite impulse response (FIR) filters are used to estimate a transfer function of an echo channel in a communications link. The LMS and NLMS algorithms are used to adapt the filter coefficients of the estimated transfer functions. By including the echo channel energy gain in the LMS or NLMS update equation, adaptation speed is increased by making adaptation responsive to the channel energy gain. An algorithm for estimating the echo channel energy gain adapts the estimate based on measured system parameters, such as a measured instantaneous channel gain and a near-end voice level. By considering in the NLMS algorithm, the average energy of either the microphone signal or the error signal, as well as the standard reference signal, a higher nominal update gain can be used. With a higher nominal update gain, the NLMS algorithm will converge more quickly.

Abstract: A hybrid echo suppresser and associated methods of use provide echo suppression in a bi-directional communications system, while minimizing desired-voice signal disruption. The hybrid echo suppresser includes a linear echo canceller (LEC), a non-linear processor (NLP), and a control circuit. The LEC operates on an echo-causing signal to produce an estimated-echo signal, which is subtracted from an input echo-containing signal, thereby producing an echo-cancelled signal. The NLP operates on this echo-cancelled signal to eliminate residual echo arising from system non-linearities. The control circuit repeatedly compares the echo-containing signal and the estimated-echo signal to determine if the echo-containing signal includes a desired-voice component. If not, the control circuit operates the NLP in an echo-voice mode having substantial signal attenuation.