Abstract: A reverberation-imparting device includes a delay line for storing a signal to which a reverberation effect is to be imparted. The delay line has at least one reading location determining timing for reading out the signal stored therein. An address generator generates basic reading address values for determining the at least one reading location. The basic reading address values are modulated by at least two different random numbers generated by a random number generator to determine reading address values. At least two signals read from the delay line are cross-faded, based on the modulated reading address values, such that the at least two signals are alternately intensified and attenuated with a predetermined phase difference. In a preferred application of the invention, the cross-faded at least two signals are output and delivered to a suitable reverberation-imparting device.

Abstract: An audio playback apparatus and method are disclosed which includes a Dolby pro-logic decoder for converting a digital audio signal into a left signal, a right signal, a center signal, and a surround signal; a sound field processor for converting the left, right, center and surround signals into a front left signal, a front right signal, a rear left signal, and a rear right signal; an audio processor for mixing the left, right, front left, front right, rear left and rear right signals according to a predetermined relationship equation and converting them into signals for two channels composed of a left-speaker output signal and a right-speaker output signal; and audio output means for outputting the left-speaker output signal via a left speaker, the right-speaker output signal via a right speaker, and the center signal via a central speaker, thereby allowing a listener to feel a rich sound presence even with fewer output speakers then with conventional audio playback apparatuses.

Abstract: When a plurality of effects are simultaneously applied to an input audio signal, a plurality of effect-algorithms each for applying solely an effect to the input signal are stored in a memory, and a plurality of combination-algorithms or combination-data which represent combinations of the effects and orders in which effects are applied to the input audio signal are stored in the memory. When one of the combination-algorithms or the combination-data is selected, effect-algorithms included in the selected combination-algorithm or combination-data are selectively read out from the memory. A program for applying effects in a predetermined combination and order is written by CPU based on the read out effect-algorithms and combination-algorithm or combination-data. Receiving the program, DSP successively applies effects to the input audio signal in accordance with the program.

Abstract: A method of simulating a room impression and/or sound impression occurring at a representative listening location in a room with monophonic, stereophonic or multichannel reproduction includes selecting a room whose sound is to be simulated. A location of a representative listening location is then determined. Subsequently, the corresponding room impulse response at least for one channel is determined at the representative listening location. A threshold value which exceeds over at least a portion of the duration of the determined room impulse response is determined for the determined room impulse response. By comparing the determined room impulse response with the threshold value, a reduced room impulse response is produced which within the portion of the duration of the determined room impulse response only includes those contents of the determined room impulse response in which a momentary amplitude is above the threshold value.

Abstract: A software reverberator system produces a sequence of "reverberated" samples from an input digital word sequence where each word in the input sequence comprises a digitized sample of an original analog audio signal. The invention generates the reverberated samples by adding together several scaled and delayed input words to produce a corresponding reverberated output word. The resulting reverberated output word stream can be converted to analog form in sequence to produce a reverberated version of the original audio signal. The delays are produced by clocking the input words through multi-stage first-in, first-out buffers with a number of stages selected to give the desired delay.

Abstract: A sound effect-creating device frequency-modulates a monaural original sound signal obtained from stereophonic sound signals, delays the resulting modulated signal by delay amounts different from each other, selects and adds up a combination of a plurality of delayed modulated signals to form signals to be added to the stereophonic sound signals, and outputs the resulting stereophonic sound signals.

Abstract: A sound field control device for reproducing plural reflected sound signals of a source signal about a listening point includes a reflected sound signal generation section for generating reflected sound signals to be sounded at front left and front right positions of the listening point and a reflected sound signal to be sounded at a rear position of the listening point, a phase shifting circuit for phase shifting the reflected sound signal to be sounded at a rear position and thereby producing a first phase shifted signal and a second phase shifted signal which are different in phase substantially by 180 degrees from each other, a first adder for adding the reflected sound signal to be sounded at a front left position and the first phase shifted signal together, and a second adder for adding the reflected sound signal to be sounded at a front right position and the second phase shifted signal together.

Abstract: A method and a system for artificial spatialization of audio-digital signals x(k) making it possible to effect on elementary signals xi(k), replicas of the audio-digital signal, different delays creating delayed elementary signals (seri) summed after weighting with the signal x(k) in order to create the spatialized audio-digital signal y(k). A plurality of linear combinations of the signals (seri) as combined delayed elementary signals (serci) is summed with the elementary signals xi(k). So as to simulate a late reverberation, the linear combinations are effected by a unit loopback, and an attenuation hi(.omega.), a decaying monotonic function of the reverberation time Tr(.omega.) to be simulated and proportional to the delay, is effected with each delay. A spectral correction before weighted summation satisfying the relation: ##EQU1## is effected, .tau.i designating the value of each delay, increased by the phase delay due to the attenuation.

Abstract: A telephone instrument creates spatially simulated sound signals from signals received from a telephone line. The received signals are directed to left and right channels. In each channel, the signals are processed via a direct path, an early reflection path including a finite impulse response filter and a reverberant decay path including all-pass filter. In each channel, the outputs from the three paths are summed with different weights.

Abstract: An echo generating apparatus includes an echo effect generator for producing reverberative echo effect by delaying an input audio signal; a band limit filter for limiting the frequency band of the output signal of the echo effect generator; a first calculator for delivering an output signal by calculating the input audio signal and the output signal of the band limit filter; and a frequency characteristic compensator for emphasizing the signal of the frequency band attenuated by the band limit filters. The echo effect generator consists of a second calculator for calculating the input audio signal and the output signal of the band limit filter, an analog delay means for delaying the output signal of the second calculator, and a clock generator for generating an operation clock signal for the analog delay means. A long reverberative echo time is maintained without the necessity of increasing the number of signal delay stages or enlarging the scale thereof.

Abstract: An audio signal processor capable of both sampling and audio processing external audio signals is disclosed. The audio signal processor can sample an audio signal and store it in a fixed store in a two function memory for later playback or manipulation. The processor can also audio process external signals in real time by splitting an incoming signal into two parts; processing one part such that it is time delayed and/or pitch shifted, or both, with respect to the unaltered part; and recombining the processed part and the unaltered part to achieve time delay effects such as flanging, chorus and echo. Moreover, the audio signal processor can output samples from the fixed store and real time processed signals simultaneously to achieve complex sound combinations and auditory effects.

Abstract: The present invention discloses a sound environment simulator including a sound field analyzing unit, a sound field reproducing unit, and an output unit. The sound environment analyzing unit divides the solid surfaces of a space to be analyzed into a set of sections to compute the volume of reflected sounds with a sound absorption coefficient of walls and form factors. It further computes time series data related to the arrival volume of sounds emanated from a certain sound source to the sound receiving point. An impulse response computing unit in the sound field reproducing unit transduces the time series data into an impulse response. Accordingly, the sound field reproducing unit convolutes the impulse response on a dry source in accordance with data related to a listener's position inputted from an associated virtual reality equipment to generate a reproduced sound over a headphone.

Abstract: A sound field control device for simulating a sound field of a small space such as a concert hall in a large space such as an open outdoor space and a large indoor space comprises loudspeakers for controlling a sound field disposed at or in the vicinity of positions in a real space corresponding to positions on a hypothetical peripheral plane which defines a hypothetical space in the real space, and a hypothetical reflected sound synthesizing section for synthesizing hypothetical reflected sounds on the basis of the sounds from a real sound source and supplying the synthesized hypothetical reflected sounds to the loudspeakers. The hypothetical reflected sounds are synthesized so that they will simulate sounds which are emanated from the real sound source and reflected from the hypothetical peripheral plane of the hypothetical space. A natural sound field in which one feels as if he was in an indoor concert hall can be obtained in the whole hypothetical space.

Abstract: A positional effect sound generation apparatus for an electronic musical instrument includes a function selector for selecting a function according to a user's selection, a note sensing circuit for sensing a note corresponding to a key on a keyboard pushed by a performer, a storage unit for storing a plurality of control signals, a CPU for selecting ones of the control signals in the storage unit corresponding to the selected function and the sensed note, a ROM for storing a plurality of sound data, a sound generator for selecting a desired one of the sound data in the ROM in response to the control signal from the CPU and generating a sound signal according to the selected sound data, a sound processing circuit for processing the sound signal from the sound generator and generating an analog echo effect sound signal, a mixer for mixing the processed sound signal with the analog echo effect sound signal, a display controller for controlling a display unit in response to the control signal from the CPU to disp

Abstract: A sound echo machine as an acoustic signal processing unit of the present invention comprising an adder to which an input signal is fed, and a delay circuit for delaying the signal fed from the adder for a certain time to repeatedly feed back to the adder to generate an echo sound further comprises an input signal level detector for detecting the level of the input signal and sending it to a frequency oscillator to vary the oscillating frequency in accordance with the thus detected signal level for feeding it later to the delay circuit so as to modulate the time to be delayed at a predetermined cycle, whereby it can create an acoustic field in which a listener can feel as if various level of reflected sounds are coming towards him from various directions.

Abstract: A sound effect-creating device amplitude-modulates a monaural original sound signal obtained from stereophonic sound signals, delays the resulting modulated signal by delay amounts different from each other, selects and adds up a combination of a plurality of delayed modulated signals to form signals to be added to the stereophonic sound signals, and outputs the resulting stereophonic sound signals.

Abstract: An analog signal to be delayed thereby is compressed according to a monotonously increasing, convex compression function and sent to a delay circuit constituted digitally. Data of a digital value stored in a memory is read out after a constant delay time and converted into an analog signal by a D/A converter. The analog signal is expanded according to a reverse function of the compression function to restore it as an echo signal.

Abstract: A sound echo machine as an acoustic signal processing unit of the present invention comprising an adder to which an input signal is fed, and a delay circuit for delaying the signal fed from the adder for a certain time to repeatedly feed back to the adder to generate an echo sound further comprises an input signal level detector for detecting the level of the input signal and sending it to a frequency oscillator to vary the oscillating frequency in accordance with the thus detected signal level for feeding it later to the delay circuit so as to modulate the time to be delayed at a predetermined cycle, whereby it can create an acoustic field in which a listener can feel as if various level of reflected sounds are coming towards him from various directions.

Abstract: A sound localization control apparatus is used to localize the sounds, which can be produced from a synthesizer and the like, at a target sound-image location. The target sound-image location is intentionally located in a three-dimensional space which is formed around a listener who listens to the sounds. The sound localization control apparatus at least provides a controller, a plurality of sound-directing devices and an allocating unit. The controller produces a distance parameter and a direction parameter with respect to the target sound-image location. The allocating unit allocates acoustic data (e.g., two-channel binaural signals), representing the sounds to be localized, to the sound-directing devices in response to the distance parameter and the direction parameter. Each of the sound-directing devices is applied with each of predetermined sounding directions which are arranged in a horizontal plane with respect to the listener.

Abstract: A system for use with headphones provides sound imaging positioning that can accurately locate the sound image at any one of a number of points surrounding the listener and can smoothly fade the sound position from one point to the next as the apparent sound source moves relative to the listener during panning. Individual sound positioners are provided that include only scalers or delay lines are provided for each channel, so that the same sound location filters can be utilized with a number of voices or input channels.

Abstract: In an acoustic reproduction system, an audio signal obtained from a source is ornamented by a sound processing pattern such as reflecting and reverberating sounds and then the sound processed audio signal is reproduced through a selected equalizing frequency curve. In particular, a plurality of equalizing curves are respectively stored in association with a plurality of predetermined specific sound processing patterns. Thus, the equalizer in response to the selected sound processing pattern automatically determines a equalizing curve corresponding to the selected sound processing pattern.

Abstract: A sound effect-creating device adds a reverberation tone signal to a monaural original tone signal by the use of a reverberation circuit, and delays a monaural reverberation tone signal output from the reverberation circuit by different delay amounts by the use of a plurality of delay circuits. At least one of delayed monaural reverberation tone signals from the delay circuits and the monaural reverberation tone signal are added up by a plurality of mixing circuits, and the resulting signals are delivered therefrom. The plurality of delay circuits are each constructed such that a delayed monaural reverberation tone signal output from one of the delay circuits and/or one from another of the delay circuits is/are input to the one of the delay circuits.

Abstract: A circuit for directly differentiating stereo and mono signals regardless of whether a pilot carrier signal is present. The circuit generally includes a detection circuit coupled to a control circuit. The detection circuit subtracts the left and right audio signals, and the control circuit compares the resulting difference to a reference signal. When the reference signal exceeds the difference between the left and right signals, the control circuit judges that the inputs are mono. The circuit is advantageously used to automatically disable a repercussion function of a stereo system when a mono signal is received.

Abstract: The manipulation system and apparatus receives electronic signals which are to be processed and recorded for playback as enhanced stereophonic audio signals from two laterally spaced loudspeakers in front of the listener. The system and apparatus processes those signals to produce a conditioning signal, such as which would be produced by virtual room boundaries, which is heard together with the original signals so that an enlarged listening area is perceived by the listener. By amplitude and phase control of the signal to the two real speakers, the system and apparatus provide a means for control over the enhanced sound field. This enhanced sound field is perceived by the listener as being contained within boundaries larger than those normally reproduced by stereophonic speakers.

Abstract: Stereo audio signals of right and left channels are inputted to a stereo surround system. The stereo surround system is provided with: a right side speaker group including at least two speakers arranged vertically; and a left side speaker group arranged at a left side of the right side speaker group, and including at least two speakers arranged vertically. The stereo surround system is further provided with a process device, coupled to the right side speaker group and the left side speaker group, for processing the inputted stereo audio signal of the right channel to generate at least two kinds of the surround signals to the right side speaker group, and for processing the inputted stereo audio signal of the left channel to generate at least two kinds of the surround signals to the left side speaker group.

Abstract: A process and apparatus are disclosed which provides increased perceptual location control and spatial characteristics to existing multi-channel material, said apparatus includes a plurality of input terminals adapted for receiving multi-channel audio input; at least one processing channel having gain control means, at least one processing channel having time delay means, which in combination, spatially enriches previously existing multi-channel material. The process for providing increased spatial characteristics to existing multi-channel material teaches operations in accordance with the apparatus.

Abstract: This invention includes a compression circuit for compress one of an audio signal and a mixture of the audio signal and an echo signal, a delay circuit for delaying an output signal of the compression circuit by a predetermined time and an expansion circuit having a conversion rate controlled by a DC voltage generated correspondingly to a regulation of the volume controller, for expanding the output signal of the delay circuit according to a reverse conversion function to the compression conversion function to generate the echo signal.

Abstract: A digital signal processor in which the control device transmits to and writes into the buffer memory the data necessary for multiplication or for generating addresses in the external memory, and then the data in the buffer memory is written into the internal memory during a single sampling period. This processing device contains an address comparator that compares the address set by the control device in the internal memory into which the data in the buffer memory is written, with the address in the internal memory controlled by the program, and then that produces control signals to write the data read from the buffer memory into the internal memory. The data read from the buffer memory is written into the internal memory, and is also used for multiplication or for generating addresses in the external memory.

Abstract: A method of detecting localization of an acoustic image, in which an acoustic impulse is emitted from a sound source to a dummy of a human head, an acoustic sensor is provided to a portion of the dummy's ears, and the response waveform is received by the acoustic sensor. This enables the detection of what effects are derived from interruption, reflection, and the like of a tone due to the human head. The received response waveform is analyzed and parameters for an acoustic image localization system are obtained. The acoustic image localization system comprising a delay circuit, a filter and an amplification controller sets the parameters into the delay circuit, the filter and the amplification controller, so that the detected localization of an acoustic image is reproduced.

Abstract: In a digital channel divider of the present invention, a plurality of filters are connected in parallel, which can set a desired transmission frequency response optionally for a digital input signal, so that signals outputted from each filter are outputted independently. In order to flatten the amplitude characteristic of an overall transmission frequency response of each channel and to obtain a linear phase frequency response, a time series impulse response is calculated based on an inverse characteristic and this time series impulse response is made to be a filter factor, and this filter factor and and the digital input signal are calculated by convolution operations.

Abstract: A sound field controller for generating apparent sound sources by adjusting the amplitude and delay time of a sound signal so that the sound will be perceived by plural listeners as sound coming from a location separated from the specific location of the front speakers, and for additionally controlling the effect of the apparent sound sources by evaluating the attributes of the source sound signal.

Abstract: A system for processing an audio signal for playback over headphones in which the apparent sound source is located outside of the head of the listener processes the input signal as if it were made up of a direct wave portion, an early reflections portion, and a reverberations portion. The direct wave portion of the signal is processed in filters whose filter coefficients are chosen based upon the desired azimuth of the virtual sound source location. The early reflection portion is passed through a bank of filters connected in parallel whose coefficients are chosen based on each reflection azimuth. The outputs of these filters are passed through scalars to adjust the amplitude to simulate a desired range of the virtual sound source. The reverberation portion is processed without any sound source location information, using a random number generator, for example, and the output is attenuated in an exponential attenuator to be faded out.

Abstract: Sound field correcting apparatus and method, in which at least two reflected sound generating circuits are cascade connected and output signals of the reflected sound generating circuits are added. A plurality of initial reflected sound signals for an original signal are first generated. Further many reflected sound signals are subsequently generated for the plurality of initial reflected sound signals. Those many reflected sound signals are obtained as reverberation sound portions.

Abstract: A preamplifier device employing electron tubes wherein the preamplifier has tremolo/vibrato circuits independent from reverb circuits allowing continuously variable control of either tremolo or vibrato effects simultaneous with continuously variable control of the reverb effect. A mixer control for controlling the level of reverb and a tone control is provided. Connections are provided for external switches used to disable any one of the above effects.

Abstract: An apparatus for correcting asymmetrical sound fields at a listener's position as in an automotive vehicle compartment in which right and left loudspeakers are disposed at positions angularly different relative to the listener's position, wherein stereo-sound signals from an acoustic signal source are output as acoustic signals of fundamental sounds to the right and left loudspeakers and, at same time, effective sounds, such as early reflection and reverberation sounds, are formed for right and left channels by arithmetically processing the acoustic signals of fundamental sounds, which acoustic signals of right- and left-channel effective sounds are outputted respectively to the right and left loudspeakers respectively.

Abstract: A method and apparatus for generating control voltage signals in a surround sound processor is disclosed which utilizes a on-shot monostable multivibrator for minimizing intermodulation distortion while following rapid directional change yet minimizing intermodulation distortion. The apparatus includes means for smoothing the directional information signals derived from audio input signals each with a continuously variable time constant to generate a corresponding control voltage signal, such that each time constant depends inversely upon the magnitude of the difference between the directional information signal applied thereto and the corresponding control voltage signal generated thereby.

Abstract: An electronic musical instrument is provided with a touch data generating device and a reverberation unit which generates a reverberation signal. The reverberation unit generates the signal correspond to the musical tone signal based on the touch data. The reverberation unit has a reverberation parameter forming device for forming a reverberation parameter which controls the reverberation signal based on the touch data. The parameter includes a delay period for a delay element and/or a coefficient for a multiplier. The musical instrument is allowed to add a mixing device to it, for mixing the musical tone signal and the reverberation signal. The musical instrument is also allowed to have a channel detecting device for detecting the number of instructed channels in place of the touch data generating device, thereby the reverberation signal being controlled by the number of the instructed channels.

Abstract: In the sound field control device, main signals and a surround signal are generated on the basis of input left and right 2 channel signals, and 4 channel main sound field signals and 4 channel surround sound field signals which are respectively aggregations of reflected sound signals of various directions in the respective sound fields are generated on the basis of reflected sound parameters of sound fields established with respect to the main signals and the surround signal, and the 4 channel main sound field signals and the 4 channel surround sound field signals of each corresponding channel are combined together and provided as 4 channel sound field signals to be sounded. Reflected sounds are created on the basis of reflected sound parameters of a certain established sound field regardless of sound field components contained in a source signal and output as a sound field signal.

Abstract: A system for reproducing a sound field simulating a real acousting space includes a sound collecting device, a sound recording device and a sound reproducing device. The sound collecting device includes first and second collection systems, the first collection system having non-directional microphones at respective corners of a cube defining a hypothetical three-dimensional space in the real acoustic space and the second collection system having directional microphones of the same number as the non-directional microphones concentrically within the three-dimensional space with directivity of each of the directional microphones being set in the direction of one of the non-directional microphones with which the directional microphone constitutes a pair. Collected sounds by the first and second collection systems of the sound collection device are mixed with each other and recorded on a recording medium by the sound recording device, and further provided on the sound reproducing device.

Abstract: A surround audio apparatus is comprised of an input terminal to which a stereo audio signal encoded for surround reproduction is supplied, an analog-to-digital converter for converting the stereo audio signal supplied to the input terminal into a digital audio signal, a digital signal processor for decoding the digital audio signal converted by the analog-to-digital converter in a surround stereo reproduction fashion to output a digital surround signal, a digital-to-analog converter for converting the digital surround signal from the digital signal processor into an analog surround signal, and an output terminal from which the analog surround signal from the digital-to-analog converter is delivered.

Abstract: A digital signal processing device for outputting a holding data in an output register from a DSP in synchronism with a second clock pulse having a frequency lower than that of a first clock pulse for conducting arithmetic processing in the DSP. Accordingly, data to be output from the DSP can be directly read by a microcomputer, and contents in a coefficient memory and a delay time memory, for example, can be updated in accordance with the read data. Further, the digital signal processing device can be applied to an audio apparatus such as a loudness controller and a spectrum indicating apparatus.

Abstract: The invention comprises a back-masking effect generator which produces, almost in real time, the simulated sound of an input audio signal being reproduced in reverse. The device digitally records the sound in packets of short duration with alternating packets being written to first and second static random access memory devices, respectively. After an initial state in which the first memory device is filled with the digitized input audio signal, the generator then continuously alternates between two other states. In one state, the second memory device is filled while the first memory device is simultaneously emptied to a digital-to-analog converter in the reverse order from which it was filled. In the other state, the first static random access memory is filled while the second memory device is simultaneously emptied to the digital-to-analog converter.

Abstract: In a sound effect apparatus which processes audio signals, a volume controller controls the volume of sound and a preset volume is detected by a detector. A plurality of delay lines delay audio signals by different delay times. A plurality of level converters generate reverberation sounds by decreasing the level of the delayed audio signals. Generated reverberation sounds and the input audio signal are added. The values of the level to which signals are lowered in the level converters are changed equally in response to the detected volume. When the detected volume is smaller than a specified volume, the values of the level to which signals are lowered are equally decreased. When the detected volume is larger than a specified volume, the values of the level to which signals are lowered are equally increased.

Abstract: A sound field is generated responsive to direct sound picked up by a direct-sound collecting microphone and indirect-sound picked up by an indirect-sound collecting microphone. Respective processing circuits are provided for signal processing the sound signals of the direct-sound collecting microphone and the indirect-sound collecting microphone. An adaptive filter is provided having a transfer function equal to a transfer function from a reproducing speaker to the indirect-sound collecting microphone. The output of the signal processing circuit associated with the indirect-sound collecting microphone is filtered by the adaptive filter, and the output of the adaptive filter is subtracted from the output of the indirect-sound collecting microphone. The output of the subtractor is then applied to the signal processing circuit associated with the indirect-sound collecting microphone for signal processing.

Abstract: A musical tone generating device is capable of simulating various special playing techniques for a stringed instrument in which the harmonic spectrums of produced sound is enhanced, or otherwise altered. The device includes a delay circuit wherein an input signal thereto is delayed and output; a closed loop circuit comprising multiple feedback pathways to which the output of the delay circuit is supplied and processed therein, after which the processed signal is returned toward the delay circuit as an input signal; an excitation device in response to a predetermined control signal, generating an excitation signal and supplying it to the closed loop circuit, such that the excitation signal corresponds to an excitation vibration in the stringed instrument being simulated; and a control device wherein the predetermined control signal is generated and whereby the delay interval of the delay circuit and the processing carried out in the multiple feedback pathways are controlled.

Abstract: A method and an apparatus for processing audio signals with a directional emphasis by providing other channels besides the left and the right channels. An audio signal processing apparatus is divided into two blocks: a first block for processing digital signals of the left channel and the right channel supplied at each predetermined sampling period and outputting the signals of the left channel, right channel, and other channels which are amplified or decreased to a certain level; and a second block for detecting the level difference between the left channel signal and the right channel signal, and the level difference between the sum and the difference between the channel signals, and generating coefficients for adjusting the amplifying rate of the channels. The result is that the number of bits required for the signal processing can be reduced.

Abstract: A sound field compensating apparatus is provided in which delay data produced by one of the delay means in a FIR filter, which is realized by the action of a DSP, is commonly used for producing a plurality of reflected sound data of corresponding channels. Accordingly, the maximum delay time of the delay data is lengthened without increasing the number of delay data retrieving actions per sampling period on the delay memory. Hence, an acceptable number of the reflected sound signals can be obtained for each channel.

Abstract: A multiple-channel audio reproduction apparatus has an audio demodulator for demodulating an input signal to produce audio signals for multiple channels. One or more signal-processing circuits process audio signals of one or more of these channels in a way suitable for reproduction by loudspeakers connected to other channels. Switches feed the processed audio signals to output terminals for those other channels. A switch controller turns these switches on if a loudspeaker is not connected to the channel corresponding to the original, unprocessed signal, and otherwise turns these switches off.

Abstract: An acoustic signal processing apparatus comprising infinite impulse response type digital filters and phase control device. The filters receive an acoustic signal. Outputs from the filters are synthesized to generate an output signal. The phase control device controls the phase of the output signals so as to cause limit cycle noise components generated by the filters to cancel each other on synthesizing.

Abstract: There is disclosed a digital audio equalizer comprising an analog/digital (A/D) converter for converting an analog audio signal into a digital audio data, a digital interface receiver for demodulating the digital data that have been modulated into a digital audio interface format into the original audio data, a signal input select switch for selecting one of the outputs of the A/D converter and digital interface receiver, a digital signal processor for receiving the output of the signal input select switch to digitally process equalizing function, a microcomputer for controlling the digital signal processor, a key input circuit for controlling the operation of the microcomputer, a state display circuit for displaying the parameters of the equalizer, and a digital/analog (D/A) converter for converting the digital output signals of the digital signal processor into analog audio signals.