18WuD2x

sound • sound power level 643
sound The vibratory or wave phenomenon to which
the sense of hearing is responsive. Conducted by
waves in solids, liquids, and gases; not propagated
through a vacuum.
sound absorption The nonreflection and nontransmission
of acoustic energy by a body or medium,
and the attendant conversion of the acoustic energy
into another form of energy (usually heat).
sound absorption coefficient A quantitative expression
of the extent to which a surface absorbs
acoustic energy (as opposed to reflecting, transmitting,
diffusing, or scattering it).
sound amplifier 1. An audio amplifier—especially
the sound channel of a television system. 2. A device,
such as a horn or reflector, that directly
boosts the intensity of sound at a given listening
point.
sound analyzer An instrument, often a wave analyzer
equipped with a microphone, for measuring
such characteristics of sound as amplitude, frequency
(pitch), and harmonic content (timbre).
sound articulation See ARTICULATION.
sound bars In a television picture, horizontal bars
resulting from interference between the audio
and video channels of the receiver.
sound carrier In a television signal, the frequencymodulated
carrier that transmits the audio part
of the program. Compare VIDEO CARRIER.
sound chamber An air enclosure, usually a box or
can, for modifying the acoustic qualities of sound
or of an audio signal.
sound detector The discriminator or ratio detector
that demodulates the sound signal in a television
receiver circuit.
sound-energy density Sound energy per unit volume,
expressed in joules per cubic meter or ergs
per cubic centimeter.
sound-energy flux The average rate of flow of
sound energy through a specified area, as expressed
in ergs or joules per second.
sound field A volume of space or material containing
sound waves.
sound film Motion-picture film on which a sound
track is recorded. Also see OPTICAL SOUND
RECORDING.
sound flux The rate of flow of sound energy, usually
expressed in terms of sound pressure at a
point or over a unit area normal to the direction
of sound propagation.
sound gate An optical device used to convert the
sound track of a movie film into electrical impulses.
sound generator Any combination of oscillator,
amplifier, and transducer (loudspeaker or headphones)
for producing sound waves.
sound-hazard integrator An instrument used to
measure cumulative noise exposure received by
persons in noisy environments. One such instrument
provides direct readings in percent of permissible
exposure.
sound IF amplifier In a television receiver circuit,
the separate amplifier for the sound intermediate
frequency. See, for illustration, INTERCARRIER
RECEIVER and SPLIT-SOUND RECEIVER.
sound-level meter See SOUND SURVEY METER.
sound marker A marker indicating the soundcarrier
point on a television alignment curve
displayed on an oscilloscope screen.
sound-marker generator A special radiofrequency
signal generator (or a special circuit in
a television-alignment generator) for the production
of a sound marker.
sound mirage See ACOUSTIC MIRAGE.
sound mix In sound recording or reproduction, the
composite output from an audio mixer circuit.
sound-on-film recording See OPTICAL SOUND
RECORDING.
sound-on-sound recording The simultaneous
recording (on a single track on magnetic tape) of
new material with previously recorded material.
The old recording is not erased.
sound-operated relay 1. A relay operated indirectly
from sound, through the medium of a
pickup microphone and amplifier. 2. A relay having
a delicately poised armature that operates directly
from sound vibrations.
Mic.
Audio
amplifier
To
controlled
circuits or
systems
sound-operated relay
Rectifier
Filter
dc
amplifier
Relay
sound power The total sound energy per unit time
produced by a sound source, as expressed in ergs
per second or in watts.
sound power level The extent, in decibels, by which
SOUND POWER exceeds one picowatt (10 –12 watt).