Showing papers on "Audio signal processing published in 1977"

Fundamentals of digital array processing

Abstract: With the advent of high-speed digital electronics, it has become feasible to use digital computers and special purpose digital processors to perform the computational tasks associated with signal reception using an antenna or directional array. The purpose of this paper is mainly tutorial, to describe mathematically and intuitively the fundamental relationships necessary to understand digital array processing. It is hoped that those readers with a background in antenna theory or array processing will see some of the advantages digital processing can offer, while those with a background in digital signal processing recognize the array processing area as a potential application for multi-dimensional signal processing theory.

Implantable electronic hearing aid

Abstract: An electronic hearing aid device for enabling persons having loss of hearing due to a nonfunctioning inner ear (Cochlea), but have a responsive auditory (acoustic, or eighth cranial) nerve, to hear by way of an electronic device including a microphone for receiving audio signals connected to an amplifier for converting the audio signal into an analog voltage signal. The analog voltage signal is filtered by a series of filter networks which separate the analog voltage signal into a plurality of frequency component signals each having a predetermined frequency range within the audio spectrum. The component analog voltage signals are then converted into digital pulse signals having the same frequency as the component voltage signal which are fed to the auditory nerve by way of implanted platinium (or other) wires wherein the digital pulse signals more accurately simulate the natural sound signals transmitted to the brain for interpretation.

Audio signal processing system

Abstract: An audio signal processing system for enhancing audio signals such as music by providing reverberation, generation of stereophonic or quadraphonic effects, chorusing, flanging, pitch change, vibrato and various combinations of these effects. An audio signal is passed through a compressor, to increase its signal-to-noise ratio,and then through a delay circuit. The delayed audio signal is passed through an expandor to restore the original input level. Preferably, before being applied to the compressor the audio signal passes through a pre-emphasis circuit and, after passing through the expandor, through a de-emphasis circuit, thereby emphasizing desired frequencies. In some embodiments, the processed output signal is blended with the received audio signal to provide a blended audio signal, and in some embodiments the processed audio signal is fed back to the system input for recirculation, providing reverberation. The delay circuit is preferably an analog shift register.

Digital voice protection system and method

Abstract: A digital voice privacy electronic communication system and method provides protection for an information signal. Either a clear voice signal or a scrambled digitized version of the voice signal is selected for transmission. At the receive end of the system a determination that a clear voice signal or a scrambled signal has been sent is made. This information is used to automatically switch the clear audio signal if present to an output circuit or to switch to the output circuit either a regenerated version of the scrambled signal or an unscrambled version of the information signal. The switching is done automatically so that a user does not have to manually select the proper receiver mode in response to reception of a signal, that is, whether the received signal was a clear voice signal or a scrambled signal. At the transmitter the information signal to be scrambled is analog-to-digital converted and the digital signal is then put into a scrambled form. The scrambled signal may be then processed through base stations, repeaters, satellite receivers, etc., while still in the digitally scrambled form, thereby providing a high degree of protection for such a signal. A receiver may regenerate, or reshape, the scrambled digital signals or the signal may be unscrambled in the receiver depending upon whether the receiver is part of, for example, a repeater system or is a terminal destination for the signal. The digital privacy system of this invention may also be utilized in signal voting systems, either analog or digital, while still maintaining, if necessary, the secure format of the scrambled information.

Distortion sound effects circuit

Abstract: A distortion sound effects circuit producing an output signal corresponding to an input signal but containing one of four selected types of distortion. A compressor which includes a voltage-controlled amplifier first compresses the audio input signal within preselected limits, and the distortion operations are performed on the compressed audio signal to advantageously render the subsequent distortion operations insensitive to gross amplitude fluctuations of the input signal. The compressor includes means for full-wave rectifying the compressed audio signal. The full-wave rectified signal is provided as a distorted output signal containing hard-even distortion of the type commonly achieved by severely, asymmetrically clipping a signal. A distortion circuit includes single voltage controlled square-low amplifier to which the compressed audio signal is applied performs the other three types of distortion. Soft-odd distortion is achieved by slightly and symmetrically overloading the input stage of the amplifier by an amount less than would result in clipping at the output stage. Hard-odd distortion is achieved by symmetrically and severely overloading the input of the amplifier to cause clipping at the output stage. Soft-even type distortion is achieved by squaring the compressed audio signal through modulation of the amplifier gain with the compressed audio signal while it is also applied to the amplifier signal input. A mixer having three inputs respectively coupled with potentiometers respectively fed by the amplifier output, the full-wave rectifier output and the undistorted, compressed audio signal output of the compressor circuit enables a musician to mix the three signals in any desired proportion.

Signal defect detection and compensation with signal de-emphasis

Abstract: Information processing system, for use with a source of carrier waves modulated with audio information, includes in respective audio channels a demodulator and for recovery of the audio information and track-and-hold amplifiers. Separate circuits are provided for detecting carrier drop-outs and impulse noise occurrences. The output of the detecting circuits is utilized to control the operation of the track-and-hold amplifiers to effect a masking of these occurrences. Signal de-emphasis is accomplished in each channel by means of two separate filters respectively arranged to operate on the input and output signal of the track-and-hold amplifier to minimize noise input to the track-and-hold amplifier.

Subscription TV audio carrier recovery system

Abstract: A subscription TV decoder for processing encoded audio and video signals in which the TV program audio information is received as an audio subcarrier includes means for decoding the video signal, a filter for separating the decoded video and audio signals, and a filter for separating the audio signal from the audio information subcarrier. The audio information subcarrier is multiplied to raise it to the frequency of the audio signal and is then recombined with the decoded video signal.

Color video display for audio signals

Abstract: Apparatus for producing a video display on a television receiver or equivalent from two channels of audio. The audio channels are fed through two banks of audio filters to separate the audio into descrete frequency bands. In the preferred embodiment, sixty-four filters per bank are used. Each set of frequency bands is mixed electrically to produce a third set of signals which are a function of the difference in phase or amplitude of the original two. These three sets of audio signals are then rectified to produce dc levels and are used sequentially, as red, green and blue inputs to produce a color display. The sequence is determined by a digital apparatus which provides that, in the basic configuration the horizontal position of each dot on the raster corresponds to a particular frequency, the color and intensity of each dot being a function of input audio amplitude and the relative phase or amplitude of the input audio channels. The vertical position of a display is a function of time so that linear bars of color are produced in response to the audio input. Additional digital circuits are provided to transform the basic display into numerous positional variations including repetitive images and mirror images in the vertical and horizontal planes, diagonal displays and circular displays.

Demultiplexing audio waveshape generator

Abstract: In an electronic musical instrument a demultiplexing audio waveshape generator, which accepts multiplexed frequency signals and generates a complex audio waveshape. This is accomplished by having a multiplexed frequency source with one or more outputs with each output being individually connected to a weighted resistor. The outputs of the resistors are connected in common to create a current source for presentation to an analog switch. The analog switch selects the multiplexed channels to be combined to produce the audio output signal, and through the use of gating signals can be made to create pulsed waveshapes. In the preferred embodiment of the present invention the signal from the analog switch is presented to a capacitance-resistance combination. The switched current presented to the capacitor causes an incremental charging and discharging of the capacitor which corresponds to the desired contribution of that particular channel to the audio output signal. The capacitance-resistance combination also functions as a low-pass filter to smooth the waveshape and provide some formant filtering.

Surface-Acoustic-Wave Devices for Signal Processing

Abstract: A brief review of the fundamental principles of the. design of Surface-Acoustic-Wave (SAW)transversal filters is reported and SAW devices, which are relevant to signal processing,are presented.

Impulse noise removing apparatus

Abstract: In a noise reduction system of the type in which an audio signal is delayed in time to permit detection of and reaction to impulse noise before application of the audio signal to a loudspeaker or the like, a transformed version of the audio signal is compared with its time-averaged value, and a resulting detection signal is processed into a control signal with blanking periods that vary as a function of corresponding impulse noise. The detection produces a response to both large impulses which stand out from the audio signal and small impulses which are hidden in the audio signal. The control signal tailors its response to the size of the impulse, blanking the audio signal substantially only for the duration of the impulse. Auxilliary circuitry is provided.

Multi-dimensional audio projector

Abstract: Apparatus for projecting movement of audio signals employs a plurality of variable-gain amplifier stages, the gain thereof being controlled by the states of an associated plurality of counters and decoders, to provide a spatial distribution of audio signals in such a manner that the signals are perceived as having a variety of geometric configurations, which configurations may be either dynamic or static. The apparatus is suitable for use with recorded or "live" audio signals. Various alternatives are also disclosed, including a sequencing circuit for allowing automatic variation of amplifier gain in response to various components of the audio signal itself. The apparatus may be configured for connection directly to power amplifiers, or for connection to recording devices.

Television receiver with display of audio signals

Abstract: In a television receiver for selectively displaying a received television picture and an audio signal waveform on the screen of a cathode ray tube, an audio signal to be displayed is applied to a pulse generation circuit where it is converted to a waveform display pulse signal having the phase position corresponding to the audio signal and this waveform display pulse signal is applied through a video amplifier having a brightness control circuit to the cathode ray tube during the display of the audio signal waveform. In this case, the background level of the screen of the cathode ray tube is changed to be lowered so that a viewer can clearly see the audio signal waveform.

A unique hardware and software approach for digital signal processing

Abstract: A novel concept for digital signal processing using universal hardware and flexible software is presented. A universal signal processor (USP) offers multiprocessing facilities with multiple function blocks for data and structured data processing. The basic components such as the CROSSBUS, the input/output processor, the data and structured data processor and the instruction processor are build with standard microprocessor slices. The concept of software is based on the high level language SIPROL (signal processing language) which is derived from PASCAL. The main differences with respect to the manifold problems in digital signal processing are outlined. Examples are presented which illustrate the proposed concept.

Apparatus for distributing television signal with stereophonic audio via satellite

Abstract: A system for distributing a television program with stereophonic audio via satellite includes a video base band, and audio left and right signals each frequency modulating spaced subcarriers. Special low level tone pulses are transmitted via the respective subcarriers when a television program with stereophonic audio begins and when it ends. Those receiving stations wishing to distribute stereo audio (as via cooperating local television and FM stations) merely detect and disseminate each subcarrier modulation. Receiving stations desirous of distributing monaural audio recognize the stereo program signalling pilot, and enable a left and right program summing amplifier to restore and furnish a compatable, full monaural audio signal. This invention relates to satellite communications and, more specifically, to the distribution of a television program with stereophonic audio while automatically providing monophonic compatability for receiving stations servicing areas not equipped for stereo or otherwise not desirous of effecting stereophonic signal distribution. It is an object of the present invention to provide improved television signal distribution via satellite. More specifically, it is an object of the present invention to provide apparatus and a system arrangement of distributing a television program with stereophonic audio via satellite while permitting monophonic compatability at selected receiving stations under local option which is not affected by intersubcarrier channel phase delays inherent in satellite signal radiation rendering left and right audio sum and differencing matrixing undesirable; and which does not needlessly interject transmission noise from an open subcarrier audio channel during periods of monaural transmission. The above and other objects of the present invention are realized in a specific illustrative stereophonic audio television signal distribution system which is propagated via satellite. The radiated signal ensemble includes base band video, and frequency multiplexed subcarriers respectively frequency modulated with left (or monaural) and right audio, and with low level "begin" and "end" of stereo program pilot signal tone bursts. At receiver locations distributing stereo, the audio programs are stripped off the main and subcarriers, and separately disseminated -- as via cooperating local TV and FM stations; via CATV cable, or the like. Receiving stations distributing only monaural audio only respond automatically to monaural audio when transmitted, and to the "begin" and "end" stereo program subcarrier pilots by operatively enabling and disabling left and right audio signal summing apparatus to reconstruct monaural audio during periods of stereophonic transmission.

Acoustic measuring system

Abstract: A remote terminal for use in an acoustic measuring system comprises a measuring device including an input terminal supplied with an analog signal to be measured, an A/D converter for converting the analog signal to a digital signal and an output terminal for manifesting an analyzed result of the analog signal; an analyzing apparatus is used for processing the data of the digital signal and for generating the analyzed result. The measuring device and the analyzing apparatus are coupled by MODEMs to each other through a data transmission circuit.

Television system with integrated audio signal transmission

Abstract: The television system system with integrated audio signal transmission is expanded beyond the colour system to include the transmission of audio signals during the line flyback of black/white television signals.A distinction is made at the transmitter between colour and black/white signals. For a b/w signal a reference signal is transmitted in the time region of the back porch on which the colour sync. signal is transmitted separately from the audio signal during colour transmission. The reference signal has a frequency equal to the colour carrier and colour synchronisation signal used for colour transmissions

One-Dimensional To Two-Dimensional And Two-Dimensional To One-Dimensional Mappings In Optical Signal Processing

Abstract: 1-D to 2-D mappings have been used in optical signal processing to increase the information throughput of optical systems for 1-D signals and to allow shift-variant processing of 1-D signals. We review two examples of such mappings: the spectral analysis of raster recorded signals, and frequency-variant spectral analysis. We then present two new optical signal processing operations where 2-D signals are mapping into 1-D formats for processing: a method for general space-variant processing of 2-D signals, and a novel nonframing video imaging technique.© (1977) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Signal priority device

Abstract: Disclosed herein is a signal priority device responsive to the audio output signal of a citizen band (C.B.) transceiver for switching the response of a common speaker system from the audio output signal of a radio receiver to the audio output signal of the C.B. transceiver. The disclosed signal priority device is connected between the existing audio output jacks of the radio receiver and the C.B. transceiver and a common speaker system, and automatically integrates the operation of the two separate devices. The signal priority device is transparent in the system when either the radio receiver or C.B. transceiver is turned off.

File unit for audio and video

Abstract: PURPOSE: To make good control for picking up the video and audio signal, by reading out the video and audio signal from the common magnetic disc digitallizing and recording the video and audio signal, transferring them to the memory for video and audio, and transmitting the video and audio. COPYRIGHT: (C)1978,JPO&Japio

Method and apparatus for encoding audio signals in television systems

Abstract: At the television transmitting end, the program audio signals to be encoded are limited to a range of 50 to 7,500 Hz. A 202 KHz signal is modulated by the so-limited audio signal and the resultant upper side-band is heterodyned against an upper side-band derived from modulating the 202 KHz signal by video horizontal drive signals. Only the lower side-band created by the heterodyning process is transmitted. At the receiver, the received single sideband signal is applied to a product detector whose other input receives the output of a horizontal drive oscillator operating in synchronism with the corresponding oscillator at the transmitter. The baseband audio signal is separated from the upper sideband signal at the product detector output by means of a low pass filter.

Process control system with signal conversion to standard intermediate signals carrying data as a function of time duration

Abstract: A process control system of the type arranged to accept varied forms of analog sensing signals from field sensing devices, to digitally process data represented thereby, and to supply varied forms of analog control signals to field control devices. The system is characterized by signal converter means which convert data between the varied analog forms generated by the field devices and a standard form of intermediate signal, e.g., a pulse-width signal, which carries data as a function of duration. The intermediate signals facilitate signal transmission, editing, and isolation, and permit the process control system to have a simple, noise-free, easily adaptable structure. Digital interface means then convert data between the intermediate signals and digital signals in a form suitable for use by digital data processing means.

Method and equipment for the production of multi-channel sound signal

Abstract: A method and apparatus for the recording and reproduction of an audio signal for multi-channel play-back in which both a monaural signal and a code signal are recorded on a magnetic tape, the recorded code signal having characteristics in accordance with the selective feeding of the audio signal to the various channels together with an adjusting device through which the code signal is controlled to thereby control the distribution of the audio signal throughout the multi-channel reproduction apparatus during multi-channel reproduction of the audio signal.

A microprogrammable signal processor

Abstract: Digital signal processing has cone full circle from software algorithms performed on general purpose computers through special purpose, dedicated, real time processors to the programmable signal/array processor. The Programmable Number Thresher (PNTJT) is an addition to the list and its organization and features is described. The PNUT is intended primarily for the linear front end computations required in many signal processing applications. It has a high speed, pipelined arithmetic unit which is kept busy by means of data transfers through several levels of memory - with all operations and transfers under microprogram control. In fact, a high speed bipolar microprogrammed controller is replicated several times to handle the data transfer and system management functions. The design utilizes LSI and VLSI devices that have recently become available and some are described.