Showing papers on "Audio signal processing published in 1970"

System for frequency modification of speech and other audio signals

Abstract: A system for multiplying the frequencies of a speech signal, or other audio signal, by a given multiplication factor, comprising an analog-digital converter for converting an audio signal to a digital signal having a bit rate f1 and means for temporarily storing that digital signal. The system further comprises apparatus for reading out the stored digital signal, in groups of n digits, at a bit rate f2, with means for synchronizing the readout apparatus to connect the groups of n digits in sequence. A digital-analog converter uses the digital readout to develop a speech signal modified in frequency in accordance with the rate f1/f2 but having the same time span as the original speech signal.

Television communications system

Abstract: A cable television communications system has signal processing headend equipment that emits a low frequency control signal that modulates the audio carrier. The control signal is transmitted over the cable along with the video and audio information. The control signal actuates control circuitry in a receiver. In the absence of the control signal the receiver will be disabled by reason of a disabling signal being applied to a critical circuit of the receiver. When the control signal is received, however, the disabling signal is removed and the receiver operates normally. For subscription television programs, another low frequency audio control signal may be sent over the cable to actuate another control circuit and jam a channel with another disabling signal. The second disabling signal may be manually switched out by a subscriber who at the same time activates a timing device to record the subscription viewing time.

Electrical circuit for enabling the visual display of an audio signal by a conventional television receiver

Abstract: An audio-video interface network for transforming audio signals from an audio source into a form suitable for reception and visual display by an unaltered black-and-white or color television receiver whereby multifarious kaleidoscopic visual interpretations of the audio input signals may be entertainingly displayed upon the face of the television receiver. The interface network includes an audio signal separator for separating the audio input signals into a plurality of different frequency bands, an internal pattern generator responsive to the separated audio signals for generating a plurality of electrical signals each uniquely representative of the content of the audio input signals, and a video signal generator responsive to the separated audio input signals and the plurality of electrical signals for generating a modulated radio frequency television signal representative of the separated audio input signals as well as the internally generated electrical signals.

Digital delay system for audio signal processing

Abstract: A plural sound delay system for use in sound reinforcement in auditoria and in other applications, comprising a digital encoding system for converting an analog audio signal to digital form, a progressive digital data store for storing the digital signal, plural readout means for reading data from the store after any one of a plurality of different storage intervals, and at least one decoding system for regenerating a delayed audio analog signal from one of the digital readouts.

Method and apparatus for automatic switching of radios and tape-recorders

Abstract: There is provided automatic switch means responsive to an audio output or an ''on'' state of an audio unit for turning off the power supply to another audio unit and concomitantly diverting or switching the output from the first-mentioned audio unit to the electrical-acoustic transducer which was previously supplied from the output of the second-mentioned audio unit. The invention has particular, but not inclusive, use in turning off an automobile radio when a tape-recorder is switched on and switching the outputs so that a common loudspeaker system may be used.

Monochannel audio teaching device

Abstract: A monochannel audio teaching device comprises an audio sender which multiplexes several audio signals into a single composite signal for transmission over single channel audio circuits for recording on the single channel magnetic tape, and an audio receiver which recovers the various audio signals from the single composite signal received. The sender provides inputs for two or more sources of audio information, related to, for example, multiple choice questions. Two frequency-multiplexed channels are provided and into each of these channels one or more audio signals can be fed on a time-multiplexed basis. Control signals precede each unit of information being time multiplexed. The control signals and Frequency/Time-multiplexed audio signals are combined to form a single composite signal or recording for subsequent use at the receiver. At the audio receiver the signals are demultiplexed and their control signals cooperate with student operated switches to select which unit of information is to be heard.

Sensitive threshold over-the-peak signal detection signals

Abstract: Threshold and over-the-peak detector circuits are disclosed which in a system configuration provide an interface between input low amplitude analog signals and digital decision logic. The circuits provide threshold information to the decision logic for initiating signal analysis processing at a suitable time prior to the occurrence of the signal peak. Over-the-peak output signals are generated by the system only when predetermined characteristics of the analog signals have been validated.

Twelve Sound Channels During the Vertical Sync Interval of the Television Signal

Abstract: The paper reports on a method for transmitting several audio signals within the video-signal spectrum so that, eg during satellite transmissions, audio signals associated with the picture can be transmitted and received-in several languages The audio signals, each in one idle line, are transmitted in a time-compressed form during the vertical flyback At the receiver the audio signal of the desired language is selected by a line selector, then stored eg in a MOS-storage and, in the original mode retransmitted with a bandwidth of about 13 kHz to the sound amplifier during the consecutive frame

Seismic data processing method and system

Abstract: In a digital seismic data processing system the reflected seismic signals are received in analog form. An analog-to-digital converter samples or measures at equal time intervals the analog signals and converts the sampled signals into a sequence of digital numbers. By the process of digital filtering, arithmetic operations are then used to multiply consecutive values of the digital numbers by a prescribed set of numbers and to add the resulting products together. This invention contemplates also using the process of digital filtering to produce a digital feedback signal which is converted into an analog feedback signal. The analog feedback signal is combined in real time with the arriving, noise-containing, analog seismic signal to substantially completely remove the noise from the arriving raw signal prior to processing it through the seismic data processing system.

Digital filtering in PCM telephone systems

Abstract: The advent of cheap and fast digital integrated circuits permits, at least in principle, the application of digital processing directly to PCM coded telephone signals. At present, the following applications look most promising: channel filters; digital conference circuits; receivers for MFC or touch-tone signals; and sampling rate conversion. Following a review of these fields, an account is given of the problems which exist specifically in a PCM telephone system.

Analog to digital converters having multiple units of measurement

Abstract: An analog to digital converter capable of providing a digital indication of the analog signal in any of a number of digital units (e.g., inches or meters) and having coarse-fine measuring ability is disclosed. A feedback counter, which operates either in a fast or slow mode depending on the magnitude of the error signal, operates in a single unit system while a display counter operates in alternative unit systems.

Method for transmitting television-compatible video and audio information by means of audio frequency and device for practicing the method

Abstract: A transmitter emits a high frequency carrier signal having relatively narrow modulation band of which the greater portion thereof is used for handling video information and the remainder is used for audio information. The video information is first stored in suitable storage tubes and is then retrieved and applied to the frame sweep controls of a conventional television receiver while simultaneously supplying to the audio portion thereof the audio signal above mentioned.

An All-Digital Multichannel Narrow-Band FSK Data Receiver

Abstract: The advent of large-scale integration has suggested new approaches to signal processing problems. In the data transmission field, for example, a complete modem can be built entirely of digital circuits. Not only is this approach technically feasible, but it is economically attractive, if the inherent speed of the digital devices is utilized by time-sharing the hardware among a large number of channels. This paper describes, an entirely digital multichannel narrow-band frequency-shift-keying data receiver. Input signals from each channel are converted to digital form and processed sequentially by a time-shared arithmetic umt composed of recursive digital filters. A prototype has been built and tested. If offers performance comparable to existing analog equivalents, while allowing extensive size and cost potential reductions.

Digital signal processing concepts

Abstract: Within the last few years, digital techniques have been extensively applied to the solution of signal processing problems. This paper briefly examines the relative merits of analog and digital signal processing techniques and then considers the conceptual issues involved in formulating the solution to a signal processing problem as a digital signal processor. Issues considered are the representation of a digital processor by a difference equation, formal solution of the difference equation, the system function corresponding to the processor, as well as the frequency response of the system.