Abstract: An intelligent noise reduction system (100) is provided. The system can include a gradient microphone (110) to produce a gradient speech signal, a correction unit (116) to de-emphasize a high frequency gain imparted by the gradient microphone, a Voice Activity Detector 120 (VAD) to determine portions of speech activity (701) and portions of noise activity (702) in the gradient speech signal, an Automatic Gain Control 130 (AGC) unit to adapt a speech gain (740) of the gradient speech signal to minimize variations in speech signal levels, and a controller (140) to control the speech gain applied by the AGC to the portions of noise activity to preserve a speech to noise level ratio between speech activity and noise activity in the gradient speech signal.

Abstract: An audio noise mitigation approach. For one aspect, a first voltage associated with a first power management state is provided. A signal responsive to an indication associated with at least a first type of periodic exit event is received and responsive to the signal, a transition to a second voltage associated with a second state is initiated, a rate of the transition to the second voltage being slower than a similar voltage transition initiated in response to a non-periodic exit event.

Abstract: The present invention discloses a circuit for eliminating speaker crackle during turning on or off a power amplifier and a method for the same, particularly to a circuit and method, wherein an input capacitor is used to pre-charge an output capacitor to reduce speaker crackle to an inaudible level during turning on or off a power amplifier. The present invention has a low cost and a simplified design without the penalty of bandwidth.

Abstract: A signal output circuit for controlling output of an input signal is disclosed. The signal output circuit includes an internal circuit, a digital delay circuit delaying by digital processing a control signal for controlling the operation of the internal circuit, and a switch muting the input signal in accordance with the output of the digital delay circuit.

Abstract: Method for outputting an audio signal to an audio output, comprising outputting a first audio signal to said audio output; providing a second audio signal; determining a point in time, wherein at said point in time said first audio signal or a derivative of said first audio signal or a derivative of said second audio signal is essentially equal to zero; switching, at said point in time, said audio output from outputting said first audio signal to outputting said second audio signal.

Abstract: Digital audio data with error detection bits added thereto is inputted to an error detecting and correcting device (4). The correcting device (4) corrects an error when the error is detected in the digital audio data. The digital audio data outputted from the error detecting and correcting device (4) is inputted to an impulse noise suppressing circuit (6). The suppressing circuit (6) operates for a predetermined time period when the correcting device (4) detects an error.

Abstract: An audio amplifier comprises: a first stage and a second stage amplifiers each respectively providing an output to a speaker; a first resistor electrically connected in parallel with the first stage amplifier; a second resistor electrically connected in series with an input of the first stage amplifier; a third resistor electrically connected in parallel with the second stage amplifier; a fourth resistor electrically connected in series with an input of the second stage amplifier, and also electrically connected in series with an output of the first stage amplifier; and a variable resistor electrically connected in parallel with the first resistor, the variable resistor and the first resistor forming a variable resistance parallel circuit.

Abstract: Circuits and apparatus to reduce transient output noise in an audio amplifier are disclosed. A disclosed example apparatus comprises an amplifier, and an amplifier controller to digitally change a common-mode voltage of the amplifier to reduce an output noise of the amplifier.

Abstract: A system comprises a plurality of storage drives coupled to logic. The logic implements a noise-reducing feature selected from a group consisting of a first feature that limits system performance based on a level of ambient noise, a second feature that staggers access transactions among said storage drives, a third feature that staggers spin up among the storage drives, a fourth feature that at least partially cancels noise generated by the system, a fifth feature that limits fan speed, and combinations thereof.

Abstract: An amplifier start-up apparatus for reducing transient signals in an audio circuit including a reference voltage generator circuit for generating a reference voltage. The reference voltage generator circuit includes a capacitor for maintaining the reference voltage at a desired level. The amplifier start-up apparatus includes a charging control circuit for controlling the operation of the reference voltage generator circuit during power-up. The charging control circuit includes a switching device for controlling the charging of the capacitor, wherein the switching device is controlled by a pulsed signal. The pulsed signal is a pulse width modulated (PWM) signal in which the pulse width is proportional to the voltage level of the reference voltage being generated. The amplifier start-up apparatus can further be adapted to include a discharging control circuit for controlling the discharge of the capacitor during a power-down operation.

Abstract: A circuit for eliminating noise includes a sound card (30) with an audio signal output, a power supply (10) for providing working voltage to the sound card, a first transistor (Q1), a second transistor (Q2), and a third transistor (Q3). The power supply has a power good pin, a PSON# pin, and a standby voltage pin. During powering on time of the sound card, the power good pin is at low level and the second transistor is therefore turned on to ground the audio signal output so as to eliminate turn-on noise. During powering down time of the sound card, the PSON# pin turns from low to high level to turn on the third transistor before the audio power for providing working voltage to the sound card is powered down, thus the first transistor turns off, and the second transistor turns on to ground the audio signal output of the sound card so as to eliminate turn-off noise.

Abstract: An automatic arrangement for deactivating a computer's speaker or microphone immediately upon the unplugging of an external headphone, speaker or microphone from the computer. Similar principles can be employed in other contexts where there is a desire to afford different types or levels of audio output to different parties or in different settings.

Abstract: An audio signal output circuit capable of decreasing pop noise includes an acoustic output device for generating sound, an audio signal generating circuit coupled to the acoustic output device for outputting audio signals, and a noise reduction circuit coupled between the acoustic output device and the audio signal generating circuit for smoothing dc level variation of audio signals outputted from the audio signal generating circuit.

Abstract: An apparatus and a muting circuit. The apparatus comprises an amplifier, a mute circuit, a pull-down circuit, and a power detection circuit. The amplifier receives a power supply voltage and a common mode voltage, and amplifies an audio input signal to generate an audio output signal. The mute circuit, coupled to the amplifier, conducts the audio output signal to about ground level upon receiving a mute signal. The pull-down circuit, coupled to the amplifier, pulls the common mode voltage to about ground level upon receiving a pull-down signal. The power detection circuit, coupled to the mute circuit and the pull-down circuit, detects power-up or power-down of the power supply voltage, and generates the mute signal and a pull-down signal according to the power-up or power-down operation.

Abstract: Noise reduction for a switching amplifier system having a differential output stage and demodulator filter responsive to complementary PWM signals includes generating in-phase PWM signals and gradually adjusting their duty cycle between a low duty cycle and the full duty cycle of the complementary PWM signals, generating full duty cycle PWM signals and gradually shifting their relative phase between in-phase and out-of-phase; and in response to a turn-on signal, adjusting the in-phase PWM signals from low to full duty cycle and shifting the relative phase from in-phase to out-of-phase, and in response to a turn-off signal shifting the relative phase from out-of-phase to in-phase and adjusting the in-phase PWM signals from full to low duty cycle for maintaining balanced charge on the demodulation filter to reduce audible noise.

Abstract: An NchMOS transistor (1) is provided for muting of an output terminal (10) to which positive and negative output signals are outputted, and a mute switch circuit (3) is provided for controlling on/off of the transistor (1) by switching a voltage applied to the gate of the transistor (1). When muting is turned off, the back gate of the transistor (1) is biased by resistance division between resistors (R1 and R2) connected in series between the output terminal (10) and a predetermined negative potential (VSS).

Abstract: An inrush current restraining circuit (100) includes a power source (Vcc), a charging/discharging circuit (11), a switching circuit (13), a first impedance component (Z1), a second impedance component (Z2), and a controller (10). The charging/discharging circuit is connected to the power source. An input of the switching circuit is connected to the charging/discharging circuit, and an output of the switching circuit is defined as an output of the inrush current restraining circuit. One end of the first impedance component is connected to the power source. The second impedance component is connected between the other end of the first impedance and the switching circuit. The controller is connected a joint of the first impedance component and the second impedance component, for providing a control signal.

Abstract: A robot includes first and second microphones and movable portions. The first microphone gathers a first sound reception signal by gathering mainly a target signal. The second microphone gathers a second reception sound signal by gathering mainly noise other than the target signal. The movable portions operate on the basis of the first sound reception signal output from the first microphone and the second sound reception signal output from the second microphone.

Abstract: A muting circuit comprising: a DC offset eliminating unit including an HPF (High Pass Filter) constituted by a first operational amplifier to eliminate a DC offset component of an AC input signal, the DC offset eliminating unit being configured to output an output signal obtained by eliminating the DC offset component of the AC input signal; a muting signal generating unit including a second operational amplifier configured to generate a second DC offset identical in level to a first DC offset at the first operational amplifier, the muting signal generating unit being configured to output a muting signal indicative of the second DC offset by fixing input to the second operational amplifier at a predetermined DC level; and a selecting unit configured to select and output the output signal when muting is not executed, and to select and output the muting signal when muting is executed.

Abstract: An amplifier start-up apparatus for reducing transient signals in a circuit, for example an audio circuit, comprising a reference voltage generator circuit for generating a reference voltage. The reference voltage generator circuit comprises a capacitor for maintaining the reference voltage at a desired level. The amplifier start-up apparatus comprises a control circuit for controlling the operation of the reference voltage generator circuit during power-up. The control circuit comprises an amplifier with a positive feedback path for controlling a current flow to the capacitor.

Abstract: An audio output apparatus having an audio codec for generating audio signals delivered to a speaker is provided with a device for preventing an audio pop noise caused by the bias voltage output from the audio codec, which includes a capacitor connected between an output end of the audio codec and the speaker, a capacitor charger for smoothly charging the capacitor to a predetermined voltage level, a switch arranged between the junction of the output end of the audio codec and the capacitor and the capacitor charger, and a control unit for controlling the codec, wherein the control unit turns on the switch and drives the capacitor charger before activating the audio codec, and then turns off the switch and terminates the operation of the capacitor charger if a predetermined charging time has elapsed.

Abstract: Provided are a circuit for and a method of eliminating pop noise in a digital audio amplifier using dual power supply, which are simple, drop in price, and can be readily implemented in a semiconductor chip. According to an existing technique, pop noise is eliminated using a relay. However, in the present circuit and method, pop noise is eliminated using the small number of discrete electronic devices. The circuit for eliminating pop noise controls a voltage at a gate of a power switch, i.e., a power MOS transistor, when power supply voltages are applied and the application of power supply voltages is stopped.

Abstract: In an amplifier circuit with reduced power-on transients, an amplifier has a gain to generate an output signal from an input signal and a reference signal when it is enabled, and a control circuit generates a control signal, based on the output signal and the reference signal, to be supplied to the amplifier during a power-on event. The amplifier is enabled by the control signal when the reference signal reaches the level of the output signal.

Abstract: An audio amplifier generates an output to a load, in which a digital-to-analog converter drives the amplifier during powering up and powering down the amplifier. The digital-to-analog converter controls the amplifier to ramp the voltage at the output at a predetermined rate to reduce rapid voltage changes from being sent to the load during the powering up or powering down sequence.

Abstract: An audio processing device for processing an audio input signal comprises one or more noise reducing means, noise level measuring means and control means connected to the noise level measuring means for controlling the noise reducing means. The audio processing device further comprises an auto signal leveling circuit to which the audio input signal is supplied, while the output signal of the auto signal leveling circuit is supplied to the noise reducing means. The auto signal leveling circuit is controlled by said control means, such that, when the noise measuring means do not detect an audio signal above a certain audio level, the auto signal leveling circuit and at least one of the noise reducing means are switched on, and, when the noise measuring means detect an audio signal above said certain audio level, the auto signal leveling circuit and the noise reducing means are switched off.

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: A circuit for audio amplification includes an amplifier and a first input resistor. The amplifier is arranged to provide an amplifier output signal that is based, in part, on a capacitively-coupled audio input signal. The capacitively-coupled audio input signal is based, in part, on an input RC value. The input RC value is given by the input capacitance times the input resistance. The input resistance is reduced during the turn-on in order to achieve a fast turn-on time with minimal pop-and-click noise. Also, the input resistance is increased to its normal value after the turn-on so that full audio fidelity is substantially maintained during normal operation.

Abstract: A signal output circuit for switching an output operation of an input signal is disclosed. The signal output circuit includes a delaying circuit for delaying a control pulse transmitted from outside, an integrating circuit for generating an integrated waveform of the control pulse of the delaying circuit, and an output operation switching circuit for switching an output operation of the input signal in accordance with the waveform output from the integrating circuit.

Abstract: This invention is a circuit that actuates a loudspeaker at input frequencies above a predetermined threshold and mutes the loudspeaker at input frequencies below the threshold. The circuit includes a comparator that generates a pulse train proportional in frequency to an input audio signal. The pulse train is then coupled to a flip flop array. The flip flop array is controlled by a clock having a specified frequency and duty cycle. The clock, in conjunction with the particular number of flip flops, creates a time window in which pulses may pass. The output of the flip flop array is coupled to an enable input of an audio amplifier. When the frequency of the pulse train is great enough to allow a number of pulses equal to or greater than the number of flip flops to pass within the window, the loudspeaker is actuated. Below this frequency, the loudspeaker is muted.

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 BTL amplifying apparatus has two power amplifiers in an BTL configuration for amplifying a speaker. It includes detection means for detecting a differential voltage between outputs from the two power amplifiers while an input signal to be supplied to the power amplifiers is muted, and decision means for deciding whether or not the differential voltage is larger than a prescribed voltage. Such a configuration prevent the speaker from being damaged.

Abstract: A method and apparatus for reducing speaker noise involves producing a control signal indicating whether or not audio program content is imminent in an audio signal operable to be transmitted to a speaker and transmitting the control signal for use by a speaker controller. The speaker controller receives the control signal and the audio signal or a speaker drive signal and provides the speaker drive signal to the speaker in response to the control signal indicating that audio program content is imminent and ceases to provide the speaker drive signal in response to the control signal indicating that audio program content is not imminent.

Abstract: A method and system are disclosed for controlling pop noises in a sound broadcasting system. After controllably connecting an output of a drive amplifier to a first predetermined low voltage level through a first switch, a first portion of an operation control data set is input to a digital-to-analog converter (DAC) circuit for driving an output thereof to a second predetermined low voltage level, and a second portion of the operation control data set is also input to the DAC circuit and further to the drive amplifier to bring the output of the drive amplifier to a common mode voltage level over a predetermined rise-up time period for controlling the pop noises.

Abstract: An audio amplifier system includes two amplifiers that are configured to drive loads through either DC or AC coupling. A third amplifier provides an AC ground return when the system is configured in the DC coupled mode, and is disabled when the system is configured in the AC coupled mode. A bypass circuit charges a bypass capacitor to provide a reference voltage level for the amplifiers. A mode detection circuit monitors the reference voltage level and the output of the third amplifier to determine the current operating mode. The third amplifier is disabled when the reference voltage exceeds the output of the third amplifier or when a shutdown condition is activated, such that the third amplifier is protected from short circuit conditions. The charge and discharge times of the bypass capacitor relate to the detected operating mode minimize click and pop in the amplified signals.

Abstract: A noise reduction system is connected to at least two input channels for receiving input signals that have substantially identical program content but differing instantaneous noise transients. The system selects a filtered input signal that has the lowest instantaneous noise transient level. In another aspect, the noise reduction system removes instantaneous transient noise from an input signal by way of a blanker. The blanker includes a switch that opens whenever a band-pass filtered input signal is greater than the average level of the signal by a predetermined proportional amount. The input signal also includes continuous noise that is removed by a continuous noise suppressor. The continuous noise is removed by a low pass filter whose corner frequency is responsive to a differentiated input signal divided by the program component signal, or vice versa.

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 generating a muting signal. The apparatus includes an audio signal detector for remotely receiving an audio signal and a processor in communication with the detector. The processor is configured to compare the received audio signal with a predetermined audio signal generated by a device and generate a muting signal when at least a component of the received audio signal matches the predetermined audio signal.

Abstract: A method of reducing a noise generated from a speaker at the time of power on/off in an audio output device that drives the speaker. The device includes a digital DC attenuator, a D/A converter, and an operational amplifier. The attenuator gradually changes an output digital value from a first digital value to a second digital value. The converter converts an output from the attenuator into an analog signal. The amplifier amplifies an output from the converter and drives a speaker. At the time of power on, the output from the attenuator is gradually changed from a digital value corresponding to the ground level to a digital value corresponding to the signal ground value. At the time of power off or system reset, the output from the attenuator is gradually changed from the digital value corresponding to the signal ground value to the digital value corresponding to the ground level.

Abstract: A control terminal driver circuit for a switching amplifier including a driver for each of a pair of output power transistors responsive to a PWM information signal. The circuit operates in response to an operating state signal indicating a start up condition for the amplifier to vary the amplitude of the drive pulses for the output transistors between a zero value and a maximum value for normal operation of the amplifier over a start up interval, and to reverse the process during a shut down interval. A DC offset detector is provided to detect a DC offset at amplifier output, and an error circuit responsive to an output of the DC offset detector controls the relative amplitude of the driver outputs during at least a portion of the start up interval to substantially eliminate the DC offset. Also disclosed is a switching amplifier including a control terminal driver circuit as described above.

Abstract: A monitor access is gradually applied an removed from a communications circuit, including a digital subscriber line (DSL), by a gradual monitor access (GMA) technique, in which a variable impedance element is gradually applied to the communications circuit until the monitor can be introduced to the communications circuit without data disruption.

Abstract: An audio signal processing method wherein it is detected whether the data supplied from an optical disk reproduction apparatus or the like has continuous zero data for a predetermined period of time, and in the case where zero data continue for the predetermined period of time, it is determined that compressed audio data is involved, and the supplied data is decoded.

Abstract: An adapter for reducing echo and noise in internet telephony for use with personal computers. The device employs analog circuitry to provide signal filters and delay which act together to reduce line induced echo and background noise, thus providing a clear voice communication channel. The device is readily inserted between standard microphones and speakers employed in the personal computer.

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 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 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 soft mute circuit includes a programmable amplifier controlled by a register. Data is stored in the register from an adder that combines the current data in the register with a second number for increasing or decreasing the gain of the amplifier. A summation circuit includes a plurality of inputs coupled by gates to a summation node and the summation node is coupled to an input of the programmable amplifier. The gates are controlled by suitable logic for selecting input signals in any combination. A control loop maintains the gain of the amplifier at a predetermined level.

Abstract: An apparatus and method for correctly sensing the state of a 4-pole earmicrophone having two receiver terminals and two common terminals for a microphone and a switch in a mobile terminal. The mobile terminal senses a switch-on of the earmicrophone by mechanical connection between an earmicrophone jack and a jack connector during an earmicrophone connection. The mobile terminal stores information about an earmicrophone state detected by the jack connector. Upon detection of the switch-on of the earmicrophone, the mobile terminal reads the earmicrophone state information from the memory. If the read earmicrophone state indicates earmicrophone disconnection, the mobile terminal mutes transmission and reception, determining that the switch-on is a transient phenomenon.

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: A method and an apparatus for controlling a sound function of a computer system based on whether or not a headphone plug is inserted into a monitor is disclosed. A switching section receives a sound signal from a main body of the computer system and outputs the sound signal to a speaker or to an inserted headphone plug based on whether or not the headphone plug is inserted by a user. A signal detecting section detects an insertion voltage signal by monitoring an insertion of the headphone plug from the switching section. A control section compares the insertion voltage signal from the signal detecting section with a predetermined reference voltage signal, and controls a speaker installed in the main body according to the compared result. Accordingly, the user can enjoy sound, such as music, regardless of the time.

Abstract: In a broadcast receiver, a dc voltage operating source is coupled to an operating voltage terminal of a sound IF integrated circuit via a collector/emitter path of a transistor, and a second source of operating voltage is connected via an RC integrating network to the base of the transistor, with the base of the transistor being connected to ground via a zener diode.