Abstract: A data reproduction apparatus includes: arithmetic means for calculating difference data that indicate a difference between left-channel and right-channel data that have been compressed in a predetermined compression format; higher harmonic component generation means for generating a higher harmonic component, which was lost during compression, by performing, when the difference data's signal level exceeds a predetermined threshold, a digital limiter process that suppresses the signal level to the threshold; and adding means for adding the higher harmonic component to the left-channel and right-channel data to reproduce original data before being compressed.

Abstract: The present invention provides a digital signal processing device that considerably reduces a return noise generated in a processing result signal in specific signal processing without wastefully increasing the processing load. There is provided a digital signal processing device that executes specific signal processing under which a return noise is generated in a processing result signal which includes an up-sampling processing unit that performs the up-sampling processing for a digital signal with a predetermined up-sampling rate to generate an up-sampling signal, a specific signal processing unit that performs the specific signal processing for the up-sampling signal generated by the up-sampling processing unit to generate the processing result signal, and a down-sampling processing unit that performs the down-sampling processing for the processing result signal generated by the specific signal processing unit with a predetermined down-sampling rate to generate a down-sampling signal.

Abstract: A sound field in a vehicle can be further readily and optimally corrected without forcing a user to do troublesome work. As an embodiment of the present invention, a measurement sound emitted through a left speaker or a right speaker at a further position in a view from a driver's listening point that was assumed on the head touching surface of the headrest of the driver's seat or the passenger seat is picked up, with a microphone provided as buried on a front panel of a head unit to be attached to the almost center position between the driver's seat and the passenger seat in the vehicle. And the frequency characteristic of the above sound is corrected, based on a tendency that the frequency characteristic of an audio sound reaching from the left speaker or the right speaker to the microphone is almost approximate to the virtual frequency characteristic of an audio sound that will reach from the left speaker or the right speaker to the driver's listening point assumed on the head touching surface.

Abstract: An audio output apparatus includes a masking band determining unit configured to determine a first frequency band in which masking due to environmental sounds is likely to occur in audio signal output sounds; a band-component extracting unit configured to extract a signal component from an input audio signal in the first frequency band determined by the masking band determining unit; a pitch shift unit configured to perform pitch shifting of the signal component in the first frequency band extracted by the band-component extracting unit and generate a pitch shift signal containing a signal component of at least a doubled frequency; and a signal output unit configured to supply an audio signal containing the pitch shift signal acquired by the pitch shift unit to a connected speaker.

Abstract: The present invention provides an audio apparatus including: a decoding device configured to decode results of channel-by-channel reproduction of a multichannel sound source made up of at least a left channel, a right channel, and a center channel, and to down-mix the decoded results of channel-by-channel reproduction in accordance with the number of speakers configured in a speaker system without a center speaker corresponding to the center channel; an audio processing device configured to perform predetermined audio processing on the decoded results having undergone the down-mixing by the decoding device, and to get the processed results output from the speaker system; and a control device configured to control the audio processing device.

Abstract: A sound field measurement apparatus includes a signal generating unit for outputting a burst signal, a driving unit for driving a speaker using the burst signal, a microphone for picking up an audio output from the speaker, an analog-digital converter for performing analog-digital conversion processing on an output signal from the microphone and outputting picked-up audio data, a filtering unit for performing filtering processing on the picked-up audio data, and an analyzing unit for determining a propagation time of the audio output from the speaker to the microphone in accordance with data output from the filtering unit. In this sound field measuring apparatus, the filtering unit is an IIR filter configured to filter the picked-up audio data forward and then backward along a time axis, or an IIR filter configured to filter the picked-up audio data backward and then forward along the time axis.

Abstract: A clipping prevention device, includes: a compression section adapted to compress an input digital audio signal level; a digital-analog conversion section adapted to operate at a predetermined first operating voltage and convert the digital audio signal into an analog audio signal; an electronic volume control adapted to operate at a second operating voltage and amplify or attenuate the analog audio signal with a user-changeable amplification factor; and a control section adapted to calculate a clipping level based on the maximum amplification factor of the electronic volume control and the user-changeable amplification factor, the maximum amplification factor being determined when the analog audio signal at the maximum signal level is amplified to the maximum signal level, and also adapted to control the compression section so that the signal is compressed so as to prevent clipping of the analog audio signal amplified or attenuated by the electronic volume control.

Abstract: An audio output apparatus includes a masking band determining unit configured to determine a first frequency band in which masking due to environmental sounds is likely to occur in audio signal output sounds; a band-component extracting unit configured to extract a signal component from an input audio signal in the first frequency band determined by the masking band determining unit; a pitch shift unit configured to perform pitch shifting of the signal component in the first frequency band extracted by the band-component extracting unit and generate a pitch shift signal containing a signal component of at least a doubled frequency; and a signal output unit configured to supply an audio signal containing the pitch shift signal acquired by the pitch shift unit to a connected speaker.

Abstract: A noise cancelling device includes a microphone; an opposite-phase circuit configured to invert a phase of a sound signal that is obtained by the microphone, thereby obtaining an opposite-phase sound signal; and a speaker configured to receive the opposite-phase sound signal that is obtained by the opposite-phase circuit, and to output a sound. The microphone is disposed at a point which is a point other than a specified listening point, the listening point being located a predetermined distance from the speaker, and at which, as a sound-pressure level of the sound that was output from the speaker, a sound-pressure level that is substantially the same as a sound-pressure level which is obtained at the listening point is obtained.

Abstract: The present invention provides a digital signal processing device that considerably reduces a return noise generated in a processing result signal in specific signal processing without wastefully increasing the processing load. There is provided a digital signal processing device that executes specific signal processing under which a return noise is generated in a processing result signal which includes an up-sampling processing unit that performs the up-sampling processing for a digital signal with a predetermined up-sampling rate to generate an up-sampling signal, a specific signal processing unit that performs the specific signal processing for the up-sampling signal generated by the up-sampling processing unit to generate the processing result signal, and a down-sampling processing unit that performs the down-sampling processing for the processing result signal generated by the specific signal processing unit with a predetermined down-sampling rate to generate a down-sampling signal.

Abstract: A power amplification circuit includes first and second clock signal generating portions operable to produce, respectively, first and second clock signals different in frequency from each other; first and second PWM signal generating portions operable to produce first and second PWM signals based on first and second input signals using the first and second clock signals, respectively; a first switching amplifier operable to perform a switching operation in response to the first PWM signal to subject the first PWM signal to power amplification to produce a first output signal and to supply the first output signal to a first circuit load; and a second switching amplifier operable to perform a switching operation in response to the second PWM signal to subject the second PWM signal to power amplification to produce a second output signal and to supply the second output signal to a second circuit load.

Abstract: A data reproduction apparatus includes: arithmetic means for calculating difference data that indicate a difference between left-channel and right-channel data that have been compressed in a predetermined compression format; higher harmonic component generation means for generating a higher harmonic component, which was lost during compression, by performing, when the difference data's signal level exceeds a predetermined threshold, a digital limiter process that suppresses the signal level to the threshold; and adding means for adding the higher harmonic component to the left-channel and right-channel data to reproduce original data before being compressed.

Abstract: Disclosed herein is an audio output device including: an equalizer configured to execute frequency characteristic correction processing for an audio signal from an audio source; an output part configured to supply an audio signal processed by the equalizer to a speaker for audio output from the speaker; a signal analyzer configured to analyze a frequency characteristic of an input audio signal to thereby obtain a gain of each of sample points on a frequency axis; and an arithmetic unit configured to control parameters of the equalizer, the arithmetic unit extracting sample points having substantially equal intervals on a logarithmic-scale frequency axis from sample points of which gains have been obtained by the signal analyzer, the arithmetic unit calculating parameters of the equalizer by using differences between gains of the extracted sample points and gains at frequencies corresponding to the extracted sample points on a target frequency characteristic.

Abstract: A sound field in a vehicle can be further readily and optimally corrected without forcing a user to do troublesome work. As an embodiment of the present invention, a measurement sound emitted through a left speaker or a right speaker at a further position in a view from a driver's listening point that was assumed on the head touching surface of the headrest of the driver's seat or the passenger seat is picked up, with a microphone provided as buried on a front panel of a head unit to be attached to the almost center position between the driver's seat and the passenger seat in the vehicle. And the frequency characteristic of the above sound is corrected, based on a tendency that the frequency characteristic of an audio sound reaching from the left speaker or the right speaker to the microphone is almost approximate to the virtual frequency characteristic of an audio sound that will reach from the left speaker or the right speaker to the driver's listening point assumed on the head touching surface.

Abstract: To realize sound output so that a listener does not feel unnaturalness, an audio signal for a center speaker is multiplied by a transfer function for a left speaker and a transfer function for a right speaker, respectively, and an audio component for a left center speaker and an audio component for a right center speaker that correspond to a listening point are generated. An audio signal for the left speaker and an audio signal for the right speaker are synthesized with the audio component for the left center speaker and the audio component for the right center speaker, respectively. Thereby, a sound image can be oriented as if a sound based on the audio signal for the center speaker is emitted from a position at which a center speaker would be set if the system had a center speaker.

Abstract: The sound field compensating apparatus includes a section that generates sound-volume regulating test signal; a driving section that drives a speaker; a microphone that receives the output from the speaker; and a control section that processes an output signal of the microphone and that controls operations of respective sections. The sound-volume regulating test signal is a sum signal representative of the sum of single-frequency sinusoidal wave signals whose frequencies are set to the relationship of an integer ratio. The control section causes the driving section to drive the speaker by using the sound-volume regulating test signal to thereby detect signal levels of frequency components of the sinusoidal wave signals from output signals of the microphone. In accordance with an average value of the signal levels, the control section sets a measuring sound volume when the speaker is driven by using the measuring test signal.

Abstract: A sound field measurement apparatus includes a signal generating unit for outputting a burst signal, a driving unit for driving a speaker using the burst signal, a microphone for picking up an audio output from the speaker, an analog-digital converter for performing analog-digital conversion processing on an output signal from the microphone and outputting picked-up audio data, a filtering unit for performing filtering processing on the picked-up audio data, and an analyzing unit for determining a propagation time of the audio output from the speaker to the microphone in accordance with data output from the filtering unit. In this sound field measuring apparatus, the filtering unit is an IIR filter configured to filter the picked-up audio data forward and then backward along a time axis, or an IIR filter configured to filter the picked-up audio data backward and then forward along the time axis.

Abstract: A power amplification circuit includes a PWM signal generating portion operable to produce from an input signal first and second PWM signals having complementary variations in their respective pulse widths, a first delaying portion operable to delay the first PWM signal by a first time to produce a first delayed PWM signal, a first switching amplifier operable to perform a switching operation in response to the first delayed PWM signal to subject the first delayed PWM signal to power amplification to produce a first output signal, and to supply the first output signal to a circuit load, a second delaying portion operable to delay the second PWM signal by a second time different from the first time to produce a second delayed PWM signal, and a second switching amplifier operable to perform a switching operation in response to the second delayed PWM signal to subject the second delayed PWM signal to power amplification to produce a second output signal, and to supply the second output signal to the circuit load

Abstract: Audio equipment and a method of controlling audio equipment include a switching power amplifier circuit and a controller controlling a switching frequency of the power amplifier circuit. The controller varies the switching frequency of the power amplifier circuit in accordance with a receiving frequency in a case of receiving at least a medium-wave broadcast wave.

Abstract: A power amplification circuit includes a PWM signal generating portion operable to produce from an input signal first and second PWM signals having complementary variations in their respective pulse widths, a first delaying portion operable to delay the first PWM signal by a first time to produce a first delayed PWM signal, a first switching amplifier operable to perform a switching operation in response to the first delayed PWM signal to subject the first delayed PWM signal to power amplification to produce a first output signal, and to supply the first output signal to a circuit load, a second delaying portion operable to delay the second PWM signal by a second time different from the first time to produce a second delayed PWM signal, and a second switching amplifier operable to perform a switching operation in response to the second delayed PWM signal to subject the second delayed PWM signal to power amplification to produce a second output signal, and to supply the second output signal to the circuit load