Abstract: Psychoacoustic models may be applied to audio signals being reproduced by an audio speaker to reduce input signal energy applied to the audio transducer. Using the psychoacoustic model, the input signal energy may be reduced in a manner that has little or no discernible effect on the quality of the audio being reproduced by the transducer. The psychoacoustic model selects energy to be reduced from the audio signal based, in part, on human auditory perceptions and/or speaker reproduction capability. The modification of energy levels in audio signals may be used to provide speaker protection functionality. For example, modified audio signals produced through the allocation of compensation coefficients may reduce excursion and displacement in a speaker; control temperature in a speaker; and/or reduce power in a speaker.

Abstract: The present invention includes a system for alerting a headphone user that another individual is attempting to gain the user's attention. The system includes an alert receiver designed to easily mate with the headphones and an audio source. The alert receiver wirelessly communicates with an alert transmitter that can be manually operated by the individual. This system enables an individual to easily alert the headphone user without requiring either party have or use a telephone.

Abstract: The invention is directed to determining a gain for an equalizer associated with an audio device. An exemplary method comprises determining a maximum audio output level allowed by an acoustic safety threshold; determining a setting of the equalizer; and adjusting a gain of the equalizer based on the setting and the maximum audio output level. The invention enables an audio device to simultaneously satisfy an acoustic safety threshold and deliver an optimum audio output level.

Abstract: In one embodiment of the present invention, a loudspeaker modeling subsystem configures a neural lumped parameter loudspeaker (NeLP) model to represent the behavior of a loudspeaker. The NeLP model is implemented as a cascaded combination of a lumped parameter model (LPM) and a neural network (NN) model. To configure the model, the loudspeaker modeling subsystem first estimates values for the parameters used in the LPM. The loudspeaker modeling subsystem then “fixes” these parameters and trains the NN model to act on a predicted output pressure that is generated via the LPM. More specifically, the loudspeaker modeling subsystem configures the NN to modify the predicted output pressure to minimize the error between the predicted output pressure and a measured loudspeaker output pressure. Notably, by strategically fusing the LPM and the NN model, the NeLP model leverages the strengths and mitigates the weaknesses typically associated with conventional loudspeaker modeling techniques.

Abstract: Methods and systems for thermal protection of a voice coil of a loudspeaker. The method involves driving the loudspeaker based on an input signal received at an input terminal and monitoring both a voltage applied to the voice coil and a current flowing through the voice coil. From the monitored voltage and current, an estimate of temperature of the voice coil and an estimate of power dissipation in the voice coil is determined. The method includes estimating the voice coil resistance based on the monitored voltage and current and at least the estimate of temperature is determined based the estimate of resistance. A gain control signal for modulating a gain applied to the input signal is generated as a function of both the estimate of temperature of the voice coil and the estimate of power dissipation in the voice coil.

Abstract: In accordance with embodiments of the present disclosure, a system may include a controller configured to be coupled to an audio speaker. The controller may be configured to receive an audio input signal. The controller may also be configured to, based on a linear displacement transfer function associated with the audio speaker, process the audio input signal to generate a modeled linear displacement of the audio speaker, wherein the linear displacement transfer function has a response that models linear displacement of the audio speaker as a linear function of the audio input signal.

Abstract: A method, system and apparatus for loudspeaker excursion domain processing are provided. At a device comprising: a processor, a loudspeaker comprising a voice coil, one or more devices for determining loudspeaker voltage and current as a function of time, t, and a memory storing a Bl product for the loudspeaker, loudspeaker currents I(t) and corresponding voltages V(t) are received at the processor from the one or more devices. A current-from-voltage transfer function HIV(?) is derived from the loudspeaker currents I(t) and voltages V(t), as a function of frequency, ?. A Fourier space excursion-from-voltage transfer function HXV(?) is determined, whose form is constrained by parameters HIV(?), Bl, Rvc, and Lvc, where: Rvc comprises a resistance of the voice coil; and Lvc comprises an inductance of the voice coil. Filter coefficients are determined using HXV(?), which are used in a filter applied to an input signal for the loudspeaker.

Abstract: A method, system and apparatus for loudspeaker excursion domain processing and thermal limiting are provided. At a device comprising: a processor; a loudspeaker and voice coil, device(s) for determining loudspeaker voltage and current; a volume device; and a memory storing a Bl product for the loudspeaker, a Fourier space excursion-from-voltage transfer function HXV(?) is determined. An acoustic response of the loudspeaker below a dovetail frequency, is determined, relative to a respective acoustic response at the dovetail frequency, using at least a second time derivative of the transfer function HXV(?). An equalization is determined using the acoustic response, comprising gains that, when applied to the acoustic response, will adjust the acoustic response to the respective acoustic response at the respective acoustic response at the dovetail frequency. Filter coefficients are determined corresponding to the equalization, which are used in a filter applied to a loudspeaker input signal.

Abstract: In accordance with embodiments of the present disclosure, a system may include an audio speaker and a controller coupled to the audio speaker. The controller may receive a current signal indicative of an electrical current associated with the audio speaker and a voltage signal indicative of an electrical voltage associated with the audio speaker. In response to the current signal and the voltage signal, the controller may estimate modeled characteristics for the audio speaker, and based on the modeled characteristics, control an audio signal communicated from the controller to the audio speaker wherein the modeled characteristics are based on discrete-time domain information and displacement domain information and the discrete-time domain information and the displacement domain information are used to update the modeled characteristics.

Abstract: The audio amplifier includes a variable gain amplifier receiving the input audio signal and providing the output signal, whereby the output signal corresponds to the input signal amplified by a limiter gain. The audio amplifier further includes a limiter gain calculation unit, thus the input signal is amplified by the limiter gain. A control unit receives a signal representative of the input signal and is configured to estimate, based on a mathematical model, the input current or the total output current of the audio amplifier thus providing an estimated current signal corresponding to (and resulting from) the output signal, whereby the limiter gain calculation unit is configured to calculate, dependent on the estimation, the limiter gain such that the actual input current or the total output current of the audio amplifier does not exceed a threshold current value.

Abstract: A programmed data processor obtains a number of input voltage measurements for a number of speaker drivers, respectively, and a sensed shared current being a measure of current in a single power supply rail that is feeding power to each of a number of audio amplifiers while the audio amplifiers are driving the speaker drivers in accordance with a number of audio channel test signals, respectively. The programmed data processor computes an estimate of electrical input impedance of each of the speaker drivers using the input voltage measurement for the speaker driver and using the sensed shared current. Other embodiments are also described and claimed.

Abstract: According to an embodiment, an active noise-reduction apparatus includes following elements. The microphone converts a sound including a target sound into an error signal. The control filter generates a control signal in accordance with a control characteristic. The first control effect estimation filter converts the control signal into a first signal in accordance with an estimated secondary path characteristic. The second control effect estimation filter converts the control signal into a second signal in accordance with a processed secondary path characteristic obtained by shortening a delay of the estimated secondary path characteristic. The updating unit updates the control characteristic based on the error signal, the first signal, and the second signal.

Abstract: A control and distribution system provides electrical power distribution, audio signal distribution, and control signal distribution to one or more audio components, such as a powered loudspeaker element or a signal conditioning device such as a rack-mounted amplifier. Embodiments allow for the monitoring and/or control of parameters and/or components at or near the endpoint of the system. These parameters or components include low-level parameters associated with the external audio devices, as opposed to merely higher level parameters of the system. The control and distribution system may include an uninterrupted power source for providing power in an online or offline mode to selected components of the external audio devices. In some embodiments, online backup power is provided to low-power components without providing power to amplifiers within the external audio devices.

Abstract: A programmed data processor receives input voltage measurements for a number of speaker drivers, wherein each of the voltage measurements may be a sensed or estimated sequence of time-domain samples of a respective speaker driver input voltage that is over a different time frame. The processor obtains a sensed shared current, being a measure of current in a single power supply rail that is feeding power to each of a number of audio amplifiers, while the audio amplifiers are driving the speaker drivers in accordance with a number of audio channel signals, respectively. The processor computes an estimate of electrical input impedance for each of the speaker drivers using the sensed shared current and the input voltage measurements. Other embodiments are also described and claimed.

Abstract: Embodiments for measuring content coherence and embodiments for measuring content similarity are described. Content coherence between a first audio section and a second audio section is measured. For each audio segment in the first audio section, a predetermined number of audio segments in the second audio section are determined. Content similarity between the audio segment in the first audio section and the determined audio segments is higher than that between the audio segment and all the other audio segments in the second audio section. An average of the content similarity between the audio segment in the first audio section and the determined audio segments is calculated. The content coherence is calculated as an average, the maximum or the minimum of the averages calculated for the audio segments in the first audio section. The content similarity may be calculated based on Dirichlet distribution.

Abstract: A system is described for maintaining synchrony of operations among a plurality of devices having independent clocking arrangements. A task distribution device is to distribute tasks to a synchrony group comprising a plurality of devices to perform tasks distributed by the task distribution device in synchrony. The task distribution device distributes each task to synchrony group members over a network. Each task is associated with a time stamp that indicates a time, relative to a clock maintained by the task distribution device, at which synchrony group members are to execute the task. Each synchrony group member periodically obtains from the task distribution device an indication of current time indicated by its clock, determines a time differential between the task distribution device's clock and its respective clock and determines therefrom a time at which, according to its respective clock, the time stamp indicates that it is to execute the task.

Abstract: Systems and methods thereof for obtaining metrics and an accurate threshold to prevent loudspeaker overheating, based on autocorrelation and cross-correlation of band-pass filtered current and voltage measurements are disclosed. The methods invented are based on instantaneous voltage and current measurements. The invention does not require a DC or pilot signal to be added to the audio signal in order to do perform the measurement, and it is not disturbed by capacitive or inductive components in the complex impedance of the voice coil.

Abstract: In accordance with embodiments of the present disclosure, systems and methods may include a controller configured to be coupled to an audio speaker, wherein the controller receives one or more signals indicative of one or more operating characteristics of the audio speaker and compares the one or more operating characteristics to one or more speaker protection thresholds, and based on the comparison, processes an audio input signal to generate an audio output signal communicated from the controller to the audio speaker, further wherein the one or more speaker protection thresholds are based on offline reliability testing of one or more audio speakers similar to the audio speaker and the controller generates one or more modeled parameters for the audio speaker and modifies the one or more speaker protection thresholds based on the one or more modeled parameters.

Abstract: The present invention is directed to a Stereo to Monaural Multi-speaker Parallel Wiring System that uses a standard 200 watt stereo and a whole sound impedance corrector to greatly reduce the wiring connections, the installation time and the overall cost of the system. A whole or complete sound comes from each speaker and will overlap from speaker to speaker so that moving around in different areas or zones within a house or yard, a person will receive the same whole and complete sound. With the master speaker switch box included, different areas or zones can be turned off or on as desired.

Abstract: The present disclosure relates to an apparatus and a method for controlling sound output. The apparatus includes a sound processor configured to amplify a sound signal to a certain level to output an output signal to a speaker. An analyzer is configured to monitor whether an output level of the output signal output from the sound processor exceeds a maximum output level of the speaker between the sound processor and the speaker, and to convert the output signal into a signal of a frequency domain to analyze an energy amount for each frequency when the output level of the output signal exceeds the maximum output level of the speaker. A controller is configured to control a volume for the output signal of the corresponding frequency band when a frequency band having the energy amount exceeding the threshold value is detected from the analyzer.

Abstract: This document discusses, among other things, apparatus and methods for providing audio transducer protection. In an example, an audio protection circuit can include a first comparator configured to compare peak power information of a drive signal of an amplifier of an audio system with a first threshold, a limiter circuit configured to limit an input of the amplifier if the peak power information of the drive signal exceeds the first threshold, and a second comparator configured to compare average power information of the drive signal with a second threshold and to provide an output signal configured to modulate a gain of a pre-amplifier of the audio system using the comparison.

Abstract: A thermal control module computes an estimate of a temperature of a speaker, based on an audio signal that is driving the speaker, and computes a gain that is applied to attenuate the audio signal to prevent overheating of the speaker. Thermal control module computes an adapted impedance, being an estimate of the speaker's impedance including its DC resistance, and uses it to compute the temperature estimate. The adapted impedance is obtained from a normal adaptation process when a measured voltage of the speaker is above a threshold, and a decay process when the measured voltage is below the threshold. Other embodiments are also described.

Abstract: A system and apparatus for constructing a displacement model across a frequency range for a loudspeaker is disclosed. The resultant displacement model is centered around the distortion point. Once a distortion model is constructed it can be incorporated into an audio driver to prevent distortion by incorporating the model and a distortion compensation unit with a conventional audio driver. Various topologies can be used to incorporate a distortion model and distortion compensation unit into an audio driver. Furthermore, a wide variety of distortion compensation techniques can be employed to avoid distortion in such an audio driver.

Abstract: A loudspeaker drive circuit has a microphone which forms part of an acoustic echo cancellation system. An input signal is processed before application to a loudspeaker driver, and the processing is controlled in dependence on the echo cancellation system performance, such as to control the extent to which the loudspeaker is driven into a non-linear operating region. In this way, the linearity can be controlled so as to provide an excursion limit, without needing a model of the loudspeaker or additional dedicated sensors.

Abstract: An apparatus comprising at least a first microphone with a first acoustic sensitivity to provide a first microphone signal and a second microphone with a lower second acoustic sensitivity to provide a second microphone signal, that apparatus furthermore comprises a signal processor that is built to process the first microphone signal to be recorded and/or transmitted and an overload detector to detect an overload of the first microphone signal and wherein the signal processor in case of a detected overload is built to process the second microphone signal to substitute the first microphone signal to be recorded and/or transmitted during the time period in which the overload of the first microphone signal is detected, which apparatus furthermore comprises at least a first speaker built to receive a first speaker signal and transform it into acoustic sound, in a speaker mode of the first speaker, while the apparatus is built to use the first speaker as second microphone, in a microphone mode of the first speaker

Abstract: A loudspeaker control system is disclosed. The loudspeaker control system includes a loudspeaker, a sensor for measuring a voltage and current and a processor. The processor is adapted to calculate an input-voltage-to-excursion transfer function over time from an admittance function, blocked electrical impedance and force factor, use the input-voltage-to-excursion transfer function over time to predict an excursion and use the excursion to control audio processing of the loudspeaker.

Abstract: A method and device are provided for detecting acoustic shocks in an audio stream. The method includes: breaking down the audio stream into audio frames; analyzing the audio frames in order to assign each audio frame a category value from among a plurality of predefined values; and determining the probability of an acoustic shock occurring in a current frame, based on a sequence of a given length of category values assigned to a set of frames, using a two-state Markov model, defined by a predetermined transition matrix and transmission matrix.

Abstract: Techniques for sensing the resistance of a load. In an aspect, a sense resistor is provided in series with the load. Each terminal of the sense resistor is alternately coupled via switches to a sense amplifier. A second input of the sense resistor is coupled to a terminal of the load. The voltage drop across the load and the voltage drop across the load plus sense resistor are alternatively measured. These voltage drops may be digitized and used to compute a resistance of the load using, e.g., a digital processor.

Abstract: A loudspeaker drive circuit comprises an input for receiving an audio signal and a signal processor for processing the audio signal before application to the loudspeaker. The signal processor processes the audio signal to derive a loudspeaker drive signal which results in the loudspeaker membrane reaching its maximum displacement in both directions of diaphragm displacement.

Abstract: A communication system for communicating with at least one loudspeaker is described where the loudspeaker is connected to audio equipment over standard two-wire speaker wire operable to carry an audio signal. The communication system includes a master node in electrical communication with a signal path carrying the audio signal between the audio equipment and the loudspeaker, the master node also including an interface with the audio equipment, a data encoder operable to encode data signals, a data transceiver operable to place the data signals onto the audio signal at frequencies above audio frequencies. The communication system also includes at least one slave node in electrical communication with the audio signal and each loudspeaker, the slave node including a data transceiver operable to receive data signals from the master node, a data decoder, and an interface able to communicate with the loudspeaker.

Abstract: An impedance matched resonant circuit uses inductors coupling an audio source and a speaker array in order to reduce feedback reflection induced by an audio signal traveling from the audio source to the array of speakers. An RC circuit could also be coupled to the positive and negative terminals of the speaker array to reduce the slope differential of the audio signal at certain frequencies. The circuit can be packaged together in a single module with switches to activate and deactivate portions of the circuit to alter the effectiveness of the circuit depending upon need.

Abstract: An audio power management system manages operation of audio devices in an audio system. The audio power management system includes a parameter computer, a threshold comparator and a limiter. Audio signals generated with the audio system may be provided to the audio power management system. Based on a measured actual parameter of the audio signal, such as a real-time actual voltage and/or a real-time actual current, the parameter computer can derive estimated operational characteristics of audio devices, such as a loudspeaker included in the audio system. The threshold comparator may use the estimated operational characteristics to develop a threshold and manage operation of one of more devices in the audio system by monitoring the measured actual parameter, and selectively directing the limiter to adjust the audio signal, or another device in the audio system to protect or optimize performance.

Abstract: An intrinsically safe audio circuit and intrinsically safe portable two-way radio device meet conventional audio output requirements and intrinsically safe design limitations by separating the speaker coil of the device's speaker into separate coils to limit the energy storage possible in any one of the coils. Each separate coil is driven by one of several different audio power amplifiers that each output a substantially identical signal, and each of which are current limited.

Abstract: In accordance with embodiments of the present disclosure, a system may include a controller configured to be coupled to an audio speaker. The controller may be configured to receive an audio input signal. The controller may also be configured to, based on a linear displacement transfer function associated with the audio speaker, process the audio input signal to generate a modeled linear displacement of the audio speaker, wherein the linear displacement transfer function has a response that models linear displacement of the audio speaker as a linear function of the audio input signal.

Abstract: For protecting a speaker, an input signal is received and filtered into component signals. A sum of the component signals is approximately equal to the input signal. The component signals include at least first and second component signals. A perceived loudness to a human from the speaker is more sensitive to the first component signal than to the second component signal. A temperature of the speaker is estimated. In response to the estimated temperature, the second component signal is scaled. An output signal is output to the speaker in response to the first component signal and the scaled second component signal.

Abstract: Peak reduction and power limitations are used to prevent distortion and protect components. In a cellular telephone, peak reduction can be based on battery power level to prevent electrical distortion from saturation. In addition peak reduction can be used to prevent mechanical distortion such as rub and buzz. Dynamic range compression can be used for peak reduction. In another application dynamic range compression can be used to control the power output to protect a speaker from damage. One example of a dynamic range compressor/peak limiter comprises a look-ahead buffer and an analysis engine. For example, the look-ahead buffer holds a window of samples of a signal. The analysis engine selects a gain envelope function on the basis of the samples, for example, by selecting the Pth sample in the buffer whenever that sample exceeds a given threshold.

Abstract: A method for adjusting the performance of an electroacoustic transducer includes receiving, by gain adjustment circuit, a displacement signal corresponding to a relative motion between a magnetic structure of the electroacoustic transducer and a voice coil of the electroacoustic transducer. The method includes detecting, by the gain adjustment circuit, a displacement signal value of the displacement signal as one of meeting or exceeding a displacement signal threshold. The method includes modifying, by the gain adjustment circuit, a loop gain of an active noise reduction loop associated with the electroacoustic transducer when the displacement signal value of the displacement signal one of meets or exceeds the displacement signal threshold.

Abstract: An exemplary personal listening device includes thermo-sensitive elements in its transducers. Each thermo-sensitive element senses temperature change of a corresponding transducer and changes a current flowing through the transducer according to temperature change of the transducer, to reflect the amount of time for which the personal listening device has been working.

Abstract: Techniques for sensing current delivered to a load by a differential output stage, e.g., in a Class D amplifier. In one aspect, voltages across sense resistors coupled in series with first and second branches of the differential output stage are low-passed filtered and digitized. The sense resistors may be coupled in series with the sources of transistors of the first and second branches, wherein the transistors are selectively switchable on and off by input voltage driving voltages. The input driving voltages may correspond to a ternary voltage waveform such that during a given phase, the two transistors coupled in series with the sense resistors may be turned off. Further aspects provide for the first and second branches having cascoded NMOS and/or PMOS transistors, and the sense resistors being provided between a pair of cascoded transistors.

Abstract: A system and method for modulating the sound pressure that is output from an audio transducer is disclosed. In one embodiment, the method includes receiving an audio signal and placing the audio signal across a voice coil of the transducer. In addition, a voltage is applied across a field coil of the transducer, the field coil being separate from the voice coil. And the voltage that is applied across the field coil is adjusted so as to modulate the sound pressure output from the audio transducer.

Abstract: An arrangement and method for converting an input signal z(t) into a mechanical or acoustical output signal p(t) comprising an electro-magnetic transducer using a coil at a fixed position and a moving armature, a sensor, a parameter measurement device and a controller. The parameter measurement device identifies parameter information P of an nonlinear model of the transducer considering and the saturation and the geometry of the magnetic elements. A diagnostic system reveals the physical causes of signal distortion and generates information for optimizing the design and manufacturing process of this transducer. The controller compensates for nonlinear signal distortion, stabilizes the rest position of the armature and protects the transducer against mechanical and thermal overload.

Abstract: A method of controlling a loudspeaker output comprises deriving an admittance function over time from the voice coil voltage and current. In combination with a delta function, the force factor of the loudspeaker and the blocked electrical impedance, the input-voltage-to-excursion transfer function over time is obtained. This is used to control audio processing for the loudspeaker thereby to implement loudspeaker protection and/or acoustic signal processing; The invention provides a modelling and control approach which is not based on a parametric model. As a consequence, it does not require prior knowledge regarding the enclosure (e.g. closed or vented box) and can cope with complex designs of the enclosure.

Abstract: An audio engine applies a driving signal to a speaker system, which produces an audio signal. The audio signal is captured by a microphone on the same device and feeds that signal back to the audio engine. After comparing the recorded signal to an expected signal the variance is assessed to determine the presence of distortion, in which case subsequent driving signals are attenuated to avoid damage to the speaker system.

Abstract: The invention relates to headphones which can facilitate the transfer of electrical power from the headphones' internal power source to other devices. A pair of headphones can connect to a device through a modified cable. The modified cable triggers the transfer of electrical power to the device. A pair headphones may have a modified port which, when connected to the device through a non-modified or regular cable, causes the transfer of power from the headphones. A power management component connected to the internal power source of the headphones helps control or regulate the transfer of power transfer to and from the headphones.

Abstract: An audio signal measurement method for a speaker and an electronic apparatus having the speaker are provided. The electronic apparatus further has a processing circuit and a power amplifier. The processing circuit is coupled to the speaker and configured to execute a time domain to frequency domain transform according to a voltage value of an audio signal and a current value of current feedback from the speaker so as to obtain a frequency response curve. The power amplifier is coupled to the speaker and configured to drive the speaker according the voltage value of the audio signal. The processing circuit is capable of determining whether the frequency response curve is located within a predetermined area such that the processing circuit generates a signal when the frequency response curve is located out of the predetermined area. Thereby, the electronic apparatus may measure its transducer distortion and acoustic box leakage.

Abstract: An original loudness level of an audio signal is maintained for a mobile device while maintaining sound quality as good as possible and protecting the loudspeaker used in the mobile device. The loudness of an audio (e.g., speech) signal may be maximized while controlling the excursion of the diaphragm of the loudspeaker (in a mobile device) to stay within the allowed range. In an implementation, the peak excursion is predicted (e.g., estimated) using the input signal and an excursion transfer function. The signal may then be modified to limit the excursion and to maximize loudness.

Abstract: A mobile device includes at least one speaker and an audio subsystem for providing an audio signal to the at least one speaker for playback by the at least one speaker. The audio subsystem operates by detecting a distance to a user of the mobile device using a proximity sensor and controlling volume output of the at least one speaker based on the distance to the user of the mobile device and the operational status of the proximity sensor. If it is determined that the proximity sensor is functional, the audio subsystem applies a gain factor to the audio signal that varies based on the distance to the user or limits the maximum allowable speaker output based on the distance. A high or low gain setting may be applied for when the user is far away or in close proximity to the mobile device.

Abstract: In accordance with embodiments of the present disclosure, systems and methods may include a controller configured to be coupled to an audio speaker, wherein the controller receives one or more signals indicative of one or more operating characteristics of the audio speaker and compares the one or more operating characteristics to one or more speaker protection thresholds, and based on the comparison, processes an audio input signal to generate an audio output signal communicated from the controller to the audio speaker, further wherein the one or more speaker protection thresholds are based on offline reliability testing of one or more audio speakers similar to the audio speaker and the controller generates one or more modeled parameters for the audio speaker and modifies the one or more speaker protection thresholds based on the one or more modeled parameters.

Abstract: In accordance with these and other embodiments of the present disclosure, systems and methods may include a controller configured to be coupled to an audio speaker, wherein the controller receives an audio input signal, and based on a displacement transfer function associated with the audio speaker, processes the audio input signal to generate an output audio signal communicated to the audio speaker, wherein the displacement transfer function correlates an amplitude and a frequency of the audio input signal to an expected displacement of the audio speaker in response to the amplitude and the frequency of the audio input signal.

Abstract: A control circuit monitors a signal produced by a MEMS or other capacitor microphone. When a criterion is met, for example when the amplitude of the monitored signal exceeds a threshold or the monitored signal has been clipped or analysis of the monitored signal indicates clipping is imminent or likely, the control circuit automatically adjusts a bias voltage applied to the capacitor microphone, thereby adjusting sensitivity of the capacitor microphone.