The acoustic equivalent of an electrical transmission line, involving baffles, labyrinths, or resonators placed at the rear of a loudspeaker and arranged to help reproduce the very low audio frequencies.

Related Terms

DISTORTION

  1. Any undesired change in the waveform of an electric signal passing through a circuit or other transmission medium.
  2. In general, the extent to which a system fails to accurately reproduce the characteristics of an input signal at its output.
  3. Any undesired change in the waveform of a sound wave.

PNEUMATIC TELEMETERING

The transmission of a pressure impulse by means of pneumatic pressure through a length of small-bore tubing; used for remote transmission of signals from primary process-unit sensing elements for pressure, temperature, flow rate, and so on.

PNEUMATIC SERVOMECHANISM

A servomechanism in which power is supplied and transmission of signals is carried out through the medium of compressed air.

PILOT WIRE REGULATOR

Automatic device for controlling adjustable gains or losses associated with transmission circuits to compensate for transmission changes caused by temperature variations, the control usually depending upon the resistance of a conductor or pilot wire having substantially the same temperature conditions as the conductors of the circuits being regulated.

PHONOGRAPH

[ENG ACOUS] An instrument for recording or reproducing acoustical signals, such as voice or music, by transmission of vibrations from or to a stylus that is in contact with a groove in a rotating disk.

PASSIVE SONAR

Sonar that uses only underwater listening equipment, with no transmission of location-revealing pulses.

NOISE REDUCTION

[ENG ACOUS] A process whereby the average transmission of the sound track of a motion picture print, averaged across the track, is decreased for signals of low level; since background noise introduced by the sound track is less at low transmission, this process reduces noise during soft passages.

MOTOR REDUCER

Speed-reduction power transmission equipment in which the reducing gears are integral with drive motors.

MISMATCH

The condition in which the impedance of a source does not match or equal the impedance of the connected load or transmission line.

MAIN

1. One of the conductors extending from the service switch, generator bus, or converter bus to the main distribution center in interior wiring. 2. See power transmission line. 3. A duct or pipe that supplies or drains ancillary branches.

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