Abstract: In a method for operating a hearing aid or hearing aid system, and a hearing aid or hearing aid system, wind noises are detected by analyzing the output signals of at least two microphones. If wind noises are present, the signal processing unit of the hearing aid or hearing aid system and/or the signal paths of microphones are adapted in order to reduce such noises.

Abstract: In the present invention, a BTL circuit formed in an IC is constituted in such a manner that a second output stage amplifier receives an output of a first output stage amplifier and generates an inverted output and a switch circuit is provided between any one of the outputs of the first and second output stage amplifier and a speaker, wherein through effecting a muting by making use of a delay time of BTL operation of the second output stage amplifier or alternatively, by making use of switches of respective push-pull structured transistors in place of the switch circuit, an early muting from the time of power source turning ON can be realized.

Abstract: A multimedia decoder unit having error concealment and fast muting capabilities. The audio decoder provides error concealment using a dynamic recovery delay that is based on the error rate of an input digital bitstream and also uses frame repeating. The decoder allows fast audio muting whereby audio can be muted within two audio frames of a mute signal that immediately freezes the video frame, e.g., a channel change. With respect to the dynamic recovery delay, a template of fixed length is used to inspect the last frames within the template. If error is found, then the error sum is used as an index into a table length which provides a dynamic template length. Error within the dynamic template length is computed and if larger than a tolerance, the current frame is muted. This allows the recovery delay to be adaptive and based on the error rate while still allowing mute merging.

Abstract: Systems and methods for detecting clipping conditions in an audio signal and processing the signal to reduce the clipping conditions. In one embodiment, a system comprises a noise shaper, a modulator, an output stage and other components. A detector detects clipping in the noise shaper and a signal processor processes the audio signal input to the noise shaper based on feedback received from the detector. The signal processor may function to modify the input audio signal in different ways in response to different conditions that are detected by the detector. A filter may be included to filter the output of the detector before being provided to the signal processor. A flag circuit may be coupled between the filter and the signal processor to assert an output signal until the signal processor resets the flag circuit.

Abstract: The present invention discloses a safety apparatus that monitors sounds in the ambient space and automatically adjusts and controls the sound output of an audio device to a predetermined level. Alternatively, the safety apparatus can provide a visual or tactile warning to the user depending on the type of input/sound detected.

Abstract: Provided is a method (500) and audio circuit (100) for reducing popping noise in a load (140, 145) connected to the audio circuit, especially during audio circuit start-up. The method applies a time varying voltage (364) to the load that has a smooth, S-shaped curve when plotted over time. The device include an integrated circuit (IC) set as a channel block (110), a load connected between the channel block and ground, a bypass control (150) connected to the channel block for producing a controlled ground reference voltage having an S-shaped curve to the channel block, a shunt control (170) controlling the voltage delivered across the load, and a ground capacitor (160) coupled between the bypass control and ground. The channel block typically includes an amplifier which supplies the output voltage across the load. The bypass circuit generally includes a bypass generator and a transistor selectively providing a charge to the ground capacitor.

Abstract: An electronic audio device with a digital audio output channel in which an amplifier output voltage is gradually ramped up and down to avoid causing a popping sound when the device is turned on and off. This is accomplished without employing any additional hardware, by incrementally changing a digital input word applied to a digital audio source, such as a DSP, so as to gradually change the amplifier output voltage between a minimum, such as zero volts, and a DC working voltage. On powering up, the amplifier is only turned on after the digital word is applied, but while it still results in a minimum amplifier output, and on powering down the amplifier is turned off after it's output has been ramped down, but before removing the digital input word. Sources and output channels can also be switched over by powering down, and then powering up, following the same method.

Abstract: Digital signal processing systems and methods for smoothing out an audio signal having an abrupt transition in volume. A DSP in an audio visual recording device is configured to smooth out discontinuous volume transitions in an audio signal during encoding. Such abrupt, discontinuous changes can occur when a user instructs the recording device to pause and resume during recording or when the user changes channels during recording. The DSP applies a transform that linearly increases or decreases the volume over one or more audio frames from the first volume level to the next volume level after the abrupt change.

Abstract: A click-muting circuit for a headset microphone connected to a telephone, comprising a user operated mute switch, a click eliminator circuit connected across the microphone for gradually creating a short circuit across the microphone in response to closure of the mute switch, and a hard muting circuit connected in series with the microphone for disconnecting the microphone after the short circuit has been established.

Abstract: An audio system limits gain in individual audio channels having a shared clip detect signal from a multi-channel power amplifier such that only channels likely to be exceeding the distortion threshold are gain limited. In addition, any arbitrary channels may be grouped together for common gain limiting. The invention monitors the power level of each audio channel, compares the power level to a power threshold that indicates whether a high power condition with the potential to cause excess distortion exists or not, and makes a decision whether to activate each channel's gain limiter based on whether the corresponding clip detect signal is active and the high power condition exists simultaneously for that channel.

Abstract: A reproducing apparatus for reproducing an audio signal from a record carrier having a first digital audio signal (a PCM encoded audio signal) recorded on it in a first format and a second digital audio signal (an MPEG encoded multi channel audio signal) recorded on it in a second format. The apparatus includes a read unit for reading an information signal from the record carrier, a decoding unit for channel decoding the information signal read from the record carrier into a decoded information signal, a keyboard for receiving a selection signal and an output terminal for supplying an output signal which comprises either the first digital audio signal or the second digital audio signal in response to said selection signal. An output circuit is available to add an identification signal (bit b1) into the output signal, indicating that the output signal includes either the first digital audio signal or another audio signal.

Abstract: A microphone system including a microphone for inputting voice data, an output for transmitting the voice data to a device connectable thereto; and a circuit which operates to mute the voice data and provide a signal to the device in order to maintain a suspended state of operation in the device. The device may be a computer that is responsive to voice data, for example, by utilizing voice recognition software.

Abstract: Disclosed is a baby monitor which includes a base unit having a microphone for receiving sound and a transmitter for conveying the sound to a remote unit, and a remote unit including a receiver for receiving the sound from the transmitter and a speaker for reproducing the sound. A timed mute system is provided for muting the speaker upon engagement of an engagement device, and for automatically unmuting the speaker after a period of time has elapsed.

Abstract: A shock sound prevention circuit which makes a BTL audio amplifier operate stable 100 msec after turning-on of a power supply is offered. The shock sound prevention circuit includes a terminal for reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which the reference voltage is applied as a bias voltage and amplifies the audio signal input from an input terminal, a second operational amplifier to which the reference voltage from the terminal for reference voltage is applied as a bias voltage and amplifies a reverse signal of the audio signal applied to the first operational amplifier, a first and a second buffers to which the reference voltage is applied, a first output terminal to which an output of the first operational amplifier and an output of the first buffer are connected together, and a second output terminal to which an output of the second operational amplifier and an output of the second buffer are connected together.

Abstract: A shock sound prevention circuit which provides a BTL audio amplifier with stable operation about 100 msec after turning-on of a power supply is required. Since the BTL audio amplifier is usually integrated in an IC, use of capacitors which takes up a large pattern area on the IC chip needs to be minimized. This invention offers a shock sound prevention circuit which has a capacitance for reference voltage to generate a reference voltage which rises according to turning-on of a power supply, a first operational amplifier to which an audio signal input and the reference voltage are applied, a second operational amplifier to which a reverse signal of the audio signal input and the reference voltage are applied, a first and a second buffers to which the reference voltage is applied and a level comparator which compares a voltage of the power supply with the reference voltage.

Abstract: The invention relates to a Muting Circuit used to control the path of signal flow for the amplified audio signals from an audio CODEC in a dual audio subsystem. More specifically, to the muting control of the rear and front panel head phone/line out and microphone connectors for the audio subsystem of a standard PC system. The present invention implements muting on the headphone 1 line-out jacks while allowing the Front Audio Board to be optional without the need for jumpers.

Abstract: Late audio buffer processing for intelligently muting audio output when audio buffers are not read fast enough from disk into digital signal processing (DSP) memory. Given a playback audio recorder, each channel of audio is associated with a forward and a reverse late threshold signals which are enabled when the processing of an audio buffer for that channel is delayed. When an audio buffer for that channel is delayed, the late threshold signal sets in motion the muting of that specific audio channel for a predetermined amount of time. If and when the system catches up, normal playback resumes. Otherwise, the channel stays muted.

Abstract: A mute circuit for momentarily inhibiting signal travel in the signal path having an input terminal and an output terminal in response to operation of a coil-operated relay. The signal path will preferably include a plurality of channel in parallel. A plurality of switch responsive coil-operated relays are disposed in the signal path with a separate unidirectional signal path coupling each of the coils of each of the coil-operated relays to a muting line with the coil of each said relay providing a signal on the muting line responsive to collapse of the magnetic field developed in the relay coil by the flow of current therethrough. A plurality of time controlled switching devices are responsive to a signal on the muting line from a coil to momentarily inhibit signal travel in the signal path. The timing circuit is included in the time controlled switching device to control the length of operation of the switch in response to a signal on the muting circuit.

Abstract: Transient distortion is compensated for by multiplying an exponentially-decaying phase shift onto the distorted waveform. The exponentially decaying phase shift waveform is patterned after the transient which typically takes the form of an exponential and occurs upon introduction of power to a circuit or circuit component. A digital circuit produces an appropriate exponentially-decaying waveform which is used as the input for a look up table whose output is a complex sinusoidal waveform capable of compensating for the distortion. The complex sinusoid is multiplied onto the transmitted waveform. The decaying exponential is biased so that it crosses a threshold at which point the compensating circuitry is turned off.

Abstract: An audio circuit has an function of removing noise signals before sending audio signals to a sounder. The circuit includes a mute detector for detecting a mute portion of the audio signals, an audio signal amplifier for amplifying the audio signals, and a noise canceler for canceling noise signals mixing with the audio signals by utilizing the noise signals picked up by the mute detector in the mute portion of the audio signals.

Abstract: An apparatus and method for controlling the audio noise attenuation by monitoring a buffer are disclosed. If the audio data to be reproduced, and if the user sets the operation as an automatic mode so that the operation of controlling the audio noise attenuation by monitoring the buffer is automatically executed, the operation of the loudspeaker is interrupted. In addition, if the audio data to be reproduced is stored, the loudspeaker is continuously driven regardless of the set of the mode. Furthermore, if there is no the audio data to be reproduced, and if the operation is not set as the automatic mode, the loudspeaker is operated. Accordingly, the analog noise, which may be generated when silence is outputted from the loudspeaker, can be eliminated, thereby improving the quality of the conference and the audio reproducing quality.

Abstract: A method of detecting a DC offset in an audio signal provided by an audio processing unit to an audio power amplifier, wherein the audio amplifier provides a clip detect signal back to the audio processing unit, wherein the method comprises the steps of sampling the clip detect signal to determine if the clip detect is active. Detecting a power level of the audio amplifier if the clip detect is active. Next, comparing the power level to a predetermined power threshold. Then, identifying a dc offset if the power level is less than the predetermined power threshold.

Abstract: An audio amplifier circuit comprises a voltage-gain amplifier and a current-gain amplifier in series between an input node and an output node. Power supply lines are provided for providing power to the audio amplifier circuit. An outer negative feedback loop is provided around the current gain amplifier and the voltage gain amplifier, and an inner negative feedback loop is provided around the voltage gain amplifier. A first switch is provided for selectively connecting the power supply lines to the current-gain amplifier. A second switch is provided for selectively switching the inner negative feedback loop or the outer negative feedback loop to the voltage-gain amplifier. A control circuit is also provided to control the switches during power supply switching.

Abstract: An electronic device comprises an audio amplifier, a main microprocessor and a user interface microprocessor. The UI microprocessor has a control pin for muting the audio amplifier. A muting circuit is provided for muting the audio amplifier when a signal representative of a switch to an OFF mode of the device is generated by a mode pin of the main microprocessor. A delay part is also provided in order to switch the audio amplifier to standby during a given period of time when a signal representative of a switch to an ON mode of the device is generated by the mode pin. Methods for controlling the electronic device are also proposed.

Abstract: A system and method for reducing noise in an audio signal. The system includes an encoder, a decoder and a single feedforward sidechain for generating a control signal that is used as input to a variable gain element in the encoder and in the decoder. The system is substantially audibly transparent, minimizes audible noise modulation, minimizes dynamic distortion of low frequency signals due to a level detector tracking these waveforms, minimizes distortion of signals due to phase shift in a transmission channel, minimizes distortion of fast, high-level transients due to the attack time of the level detector, and has virtually no effect on the audio signal if the level of the signal stays within a reasonable range around the nominal signal level.

Abstract: In a DVE, digital voice enhancement, communication system, the selection decision for choosing which microphone to be active is based on a given function of the speech of a respective talker relative to his/her acoustic environment at the respective microphone. The selection decision is based on a selection technique normalizing at least one of a) different microphone sensitivities and b) different background noise levels at the respective microphones, preferably based on the ratio of how much louder a talker speaks over the background noise at his/her respective microphone.

Abstract: A pop sound reduction circuit comprises a pulse width modulation amplifier configured to amplify a reference voltage to an intermediate amplitude of a pulse width modulated signal, a first switch configured to activate and deactivate the pulse width modulation amplifier, a buffer amplifier configured to generate a DC voltage equal to the reference voltage, a second switch configured to activate and deactivate the buffer amplifier, and a control circuit configured to close and open the first and second switches complementary, depending on a potential in a leading region of the reference voltage which rises from a time of turning-on of a power source as well as a potential in a trailing region of the reference voltage which falls from a time of turning-off of the power source.

Abstract: A receiver portion of a telephone includes a differential amplifier stage with a single output, an electroacoustic transducer connected between the output, via a capacitor and ground and a unit for controlling switching on/off, connected to the differential stage for the activation or deactivation thereof. To prevent annoying noises in the transducer upon switching on and off, the differential stage includes an operational amplifier having a first capacitor and a second capacitor in series with the inverting and the non-inverting input terminals. A third capacitor is connected between the inverting input and the output of the operational amplifier. A fourth capacitor is connected between the non-inverting input and a first reference-voltage terminal. A first switching capacitor is alternatively connectable between a second and a third reference-voltage terminal, or between the first input and the output of the operational amplifier.

Abstract: The present invention relates to an audio amplifier using a pulse width modulation, and more particularly, to a pulse width modulation type audio amplifier which an average switching frequency or a cutoff frequency of a low pass filter is variable in accordance with frequency of input signal.

Abstract: In order to quickly decrease voltage applied to a mute pin 18 of an audio amplifier circuit 19 of an electronic appliance, an end of a capacitor 20 connected to the mute pin is connected to a discharge circuit which is fired on when the electronic appliance is switched from on to off or stand-by by exploiting two power supply sources of the appliance. The voltage output of one of them decreases faster than the other one when the electronic appliance is switched off. An active element 27 of the discharge circuit has an electrode coupled to the first source and an other electrode coupled to the second sources so that the active element is fired on as soon as the difference between the two output voltages reaches a threshold.

Abstract: A mute switch including a field effect transistor receiving a mute control signal at its gate for selectively supplying an audio signal from an input node to an output node. A bipolar transistor is connected between the input node and the FET for reducing the voltage level of the audio signal prior to its application to the input node, and a further bipolar transistor is connected between the FET and the output node for raising the voltage level of the audio signal prior to its application to the output node. This serves to maintain the DC bias level of the audio output signal independently of the status of the mute control signal.

Abstract: The method, apparatus, and system for controlling audio anomalies by using a mute switch 51 to prevent output of an auxiliary audio signal 21 in a television signal 20 with an auxiliary audio signal 21, such as a NICAM audio signal or dual language audio signal, adjacent to a first audio signal 22. The mute switch 51 operation is a function of the type of receiver 19 receiving television signal 20 and a function of verifying the presence of an auxiliary audio signal 21 in television signal 20. The present invention controls audio anomalies such as audio whistle and audio pop.

Abstract: A filter for suppressing noise surges and noise frequencies in ac power lines to an audio video load includes at least one noise suppression circuit. The noise suppression circuit in turn includes first and second inductors coupled to respective power lines in series with the load. A capacitor is coupled between the power lines at the input of the first inductor and the output of the second inductor. With this arrangement, the capacitor suppresses noise surges in the power line, while being protected by the second inductor from being damaged by the surges. Also, the filter suppresses two noise frequencies using only the single capacitor. If desired, additional noise suppression circuits can be provided, with each noise suppression circuit suppressing two noise frequencies using only a single capacitor.

Abstract: A controller for a powered loudspeaker including a bus monitor configured to monitor a bus for activity and a click suppression unit coupled to the bus monitor and configured to control speaker volume by ramping the volume down if an absence of data on the bus is detected, and restoring the volume once bus activity begins again. In this manner, undesired clicks and hisses upon power up and power down are minimized.

Abstract: An arrangement for activating and deactivating automatic noise cancellation (ANC) in a mobile station, in which there are an ANC facility (3) for suppressing background noise in an incoming audio signal, as well as circuits for activating and deactivating the ANC, includes automatic detection (10) of the need for ANC according to a selected criterion, for example, a set noise level, the detection circuit configuration (10) being arranged to automatically control the activation and deactivation of the ANC facility (3).

Abstract: An audio amplifier device includes a power supply having an output for providing a supply voltage, a voltage divider connected to the output of the power supply for providing a divided supply voltage, and an audio amplifier that further includes a supply voltage rejection circuit. The audio amplifier has a first input for receiving an input audio signal, a second input for receiving the supply voltage, a third input for receiving a supply voltage rejection signal for the supply voltage rejection circuit, and an output for providing an output audio signal. A power-off noise suppression circuit has a first input for receiving the divided supply voltage and an output for providing the supply voltage rejection signal.

Abstract: A mute apparatus comprises a plurality of mute switches 7 each operative to assume two operation states consisting of a mute-on state and a mute-off state; a mute executing switch 6 operative to assume two executing states consisting of a mute-on state and a mute-off state; mute switch control data generating means 3 for generating mute switch control data elements indicative of the operation states of the respective mute switches 7; mute switch control data determining means 4 for determining whether a mute executing switch 6 is to assume the mute-on or mute-off state on the basis of the mute switch control data elements; and mute switch means 5 for having the mute executing switch 6 selectively assume the mute-on and mute-off states on the basis of the mute-on or mute-off state determined by the mute switch control data determining means 4, thereby making it possible for the single mute switch means 5 to determine the execution state of the mute executing switch 6 to mute or unmute an audio signal inputted

Abstract: A “floating” or “unipolar” DC supply is coupled to a filter comprising a pair of capacitors coupled in series across the supply output. Output voltages developed across the capacitors are applied to the supply inputs of an amplifier having an output coupled via a load to a common connection of the two capacitors. A bias supply, coupled in parallel with the filter, produces an output voltage representative of the relative values of the capacitor voltages which is fed back to an input of the amplifier via a threshold device. Under transient input signal conditions, which would tend to unbalance the filter capacitor voltages, the bias supply renders the threshold device conductive for diverting the transient from the amplifier input thus reducing the supply voltage imbalance and improving the transient recovery time of the amplifier.

Abstract: An audio system 100 includes digital-to-analog converters 110 having left and right paths for converting received left and right streams of digital audio data and a plurality of analog data ports for receiving left and right channel streams of analog audio data. Mixer 115 has left and right paths for selectively mixing left and right channel data passed from converters 110 and left and right channel data passed from the analog data ports. Muting circuitry is also provided for selectively muting said right and left channel data to be passed to mixer 115 from converters 110. Circuitry is also included for idling a selected one of the left and right paths of mixer 115 when selected data path to mixer 115 is muted.

Abstract: A power system the size of which does not become very large although the system uses secondary batteries, and in which the supply of DC power is not stopped at the time of charging the battery after the secondary battery is completely discharged, and an amplification system for audio using the power system. When no signal is inputted to an amplifier (1) for audio for a fixed period of time or longer, a control circuit (4) gives a connection switching signal (b) to a connection switching circuit (7) under a fixed condition, but, Whenever the signal (b) is given to the circuit (7), one of the secondary batteries (6A and 6B) is switched to the power source of the amplifier (1) from a state where the battery is charged by means of a charging circuit (8), and the other battery is switched to a state where the battery is charged by means of the circuit (8) from a state where the battery supplies electric power to the amplifier (1).

Abstract: The anti-pop circuit includes a unity gain buffer with an input coupled to the source of the reference voltage and an output coupled to the input of the amplifier to accelerate the charging of the input coupling capacitor of the amplifier at every turn-on. The capacitor-charging buffer is automatically disabled before the turning-on of the amplifier. The charging buffer may be enabled at start up by generating an impulse of a pre-established duration at the turn-on instant by a monostable circuit or by disabling it upon verifying the decaying to zero of the charging of current of the input coupling capacitor. The circuit eliminates the popping noise at the turn-on without an excessive delay of the turning-on of the amplifier.

Abstract: A controller for a powered loudspeaker including a bus monitor configured to monitor a bus for activity and a click suppression unit coupled to the bus monitor and configured to control speaker volume by ramping the volume down if an absence of data on the bus is detected, and restoring the volume once bus activity begins again. In this manner, undesired clicks and hisses upon power up and power down are minimized.