Showing papers on "Audio signal processing published in 1972"

Discrete representation of signals

Abstract: In processing continuous-time signals by digitalmeans, it is necessary to represent the signal by a digital sequence. There are many ways other than periodic sampling for obtaining such a sequence. The requirements for such representations and some examples are discussed within the framework of simulating linear time-invariant systems. The representation of digital sequences by other digital sequences is also discussed, with particular emphasis on the use of such representations to implement a nonlinear warping of the digital frequency axis. Some applications and hardware implementation of this digital-frequency warping are described.

A Simple Approach to Digital Signal Processing

Abstract: From the Publisher: Digital signal processing (DSP) has been a very active area of research and application for over thirty years Applications range from audio and video electronics to sensors, image processing and medical applications Provides a basic introduction and simple overview of DSP

Time compression of audio signals

Abstract: The invention pertains to a technique for time-compressing audio signals without disturbing the relative position of the audio samples through the use of a time buffer store and a subsequent FM recording of the time-compressed audio signal in a format similar to video signals and the subsequent demodulation of the FM signals and time expansion of the signals to produce the original audio signals. The use of FM modulation and demodulation of a type similar to that used with video information for recording and transmitting time-compressed audio information permits common processing of audio and video information and the utilization of standard video transmission and video tape and video disc recorders to accommodate audio as well as video information.

Teminology in digital signal processing

Abstract: The committee on Digital Signal Processing of the IEEE Group on Audio and Electroacoustics has undertaken the project of recommending terminology for use in papers and texts on digital signal processing. The reasons for this project are twofold. First, the meanings of many terms that are commonly used differ from one author to another. Second, there are many terms that one would like to have defined for which no standard term currently exists. It is the purpose of this paper to propose terminology which we feel is self-consistent, and which is in reasonably good agreement with current practices. An alphabetic index of terms is included at the end of the paper.

Electric animal trainer

Abstract: A radio frequency signal modulated at a predetermined audio frequency is transmitted to a receiver carried by the animal to be trained. The modulated signal is detected, amplified and demodulated, and the resulting audio signal is then amplified by a tuned audio amplifier. A trigger circuit is arranged to accept audio signals resulting from an original modulation percentage greater than a predetermined level and to create a voltage pulse at electrodes arranged to bear against the animal's fur. Means are provided for attenuating audio signals which differ from the predetermined audio frequency.

Signal converting systems for use in stereo reproducing systems

Abstract: A signal converter is provided for intermixing first and second audio signals reproduced from a conventional 2-channel recording medium to produce two difference signals which are supplied to a 2 to 4-channel converter for improving the separation between the front and rear signals. The signal converter may be constructed to mix together first and second audio signals at a variable relative amplitude ratio therebetween and with a variable polarity relationship to form two sum signals or two difference signals.

Method of reducing the interference signals during the transmission of af signals in time-compressed form

Abstract: In a known method of transmitting the sound signal associated with a television signal, the sound signal occurring during a field is stored and, subsequently to the video signal, transmitted in time-compressed form during the period of a line in the vertical blanking interval. At the place of reception, this line-by-line division of the sound signal naturally results in disturbing transients and dying-out processes. To avoid this, the invention proposes transmitting the sound signals of the individual fields with a time overlap.

Electronic musical instrument with digital reverberation system

Abstract: An electronic musical instrument with a digital reverberation system in which one of the digital signals in a pair of digital signal information channels is delayed. The system is particularly adapted for use in an electronic musical instrument in which a digital multiplex signal is generated by actuation of the keys of the instrument. The digital multiplex signal is used to address a digital wave shape memory which stores signals representative of a musical note in digital form. The signals read out of the digital wave shape memory are, after processing, converted to an analog signal by means of one or more digital to analog converters. A pair of digital channels, one of which has a digital delay means therein, may be incorporated into an electronic musical instrument at various stages. The delay may be incorporated into one of the digital channels before or after the reading of the digital wave shape from memory. In addition, means may be provided to selectively switch between the delayed and undelayed signals as desired for the pedals, great or lower manual, and the swell or upper manual by means of a multiplex keyboard selector which in conjunction with an electronic switch selectively switches in the delay for the portion of the multiplex signal corresponding to a particular keyboard.

Noise eliminating device

Abstract: In a noise reducing device for reducing noises contained in audio signals, a frequency band wherein noises contained in audio signals are highly sensible to an auditor, but the frequency of appearance therein of the audio signals is substantially low is blocked by a required number of band-elimination filters provided in series in a transmission line for transmitting the audio signals, each of the band-elimination filters being bypassed by a corresponding variable impedance circuit, while the same frequency band is passed through a corresponding number of band-pass filters, the outputs of said band-pass filters being supplied respectively to corresponding control signal producing circuits to produce control signals, whereby said variable impedance circuits bypassing the band-elimination filters are controlled respectively by said control signals, and the band-elimination filters are thereby brought into a state effectively blocking the frequency band when the input audio signal level in said frequency band is lower than a predetermined value and vice versa.

Audio-digital recording system

Abstract: A system for converting an input analog signal, such as an audio signal or signal representative of sound into a digital form for storing in digital form and for reconstructing the input analog signal from the digital form is disclosed. The system includes sampling means for converting the input audio signal into a binary format which includes ranging bits and adjusted magnitude bits. This permits the recording in digital form of audio signals of a wide dynamic range with a reduced number of bits. Additionally, the disclosed encoding method for encoding digital words prior to recording reduces pulse crowding on magnetic tape and achieves higher bit packing densities. The system may be used with existing professional audio tape drives with tape speeds of approximately 30 ips or less.

Circuit arrangement for analog-to-digital conversion of magnitudes or signals in electrical form

Abstract: Apparatus for converting analog electrical signals to a digital electrical signal wherein the statistical probability of a predetermined state for the digital output signal is a predetermined function of the analog input signals to provide digital signals having improved transmission capabilities. A continuously varying threshold electrical signal having a predetermined statistical distribution of amplitudes is compared to the analog input signal and the result of such a comparison is used to produce and control the digital output signal such that the statistical probability of a given digital state is a predetermined function of the analog input corresponding to the predetermined statistical distribution of amplitudes of the continuously varying threshold signal.

Recognition system and processor

Abstract: A recognition system for viewing and processing information on an article such as a letter or the like including an optical system for viewing the information, a diode array for converting the viewed image of the information into analog electrical signals, an amplifier for amplifying the analog electrical signals, an input conditioner for converting the amplified analog electrical signals into digital signals and a processor for processing the digital signals to compensate for errors which might be present in the information on the article and in the analog and digital signals.

Application of pulse-code modulation to sound-signal distribution in a broadcasting network

Abstract: The application of digital methods to the internal distribution of high-quality sound signals in a broadcasting system allows a high and predictable standard of technical quality to be maintained with the minimum of attention by operating staff. Pulse-code-modulation systems for the incorporation of a sound signal into a video waveform and for the multiplex distribution of programmes for the radio service will soon be in operation within the BBC, and the eventual use of national and international digital links for this purpose is envisaged. The feasibility of digital recording has also been demonstrated. This paper is mainly concerned with the special requirements to be met in the digital coding and decoding of broadcast-quality sound signals. Considerations of quantising noise, distortion and digit-error detection lead to a bit rate approaching half a megabit per second per channel, though this rate may be somewhat reduced as a result of current developments in digital companding. No attempt is made to deal with aspects of point-to-point transmission which are common to other digital systems, but the effects of digit-error rate and of timing jitter are considered, and tolerances are suggested.

Signal Processing Element Functional Description. Part 2 (Preliminary). Signal Processing Arithmetic Unit

Abstract: : The NRL Signal Processing Element (SPE) is being developed to provide a high-performance signal processing facility for radar, sonar, and communication systems It is intended to be compatible with the Navy's All Applications Digital Computer (AADC) The SPE consists of four major subsystems; a Microprogrammed Control Unit (MCU), a Buffer Store and Storage Control Unit (SPU), a Signal Processing Arithmetic Unit (SPAU), and Input/Output (I/O) units