18WuD2x

644 sound pressure • source follower
sound pressure 1. The force exerted by sound
waves on a surface area, expressed in dynes per
square centimeter (as an rms value over 1 cycle).
The sound pressure is proportional to the square
root of sound-energy density. 2. The instantaneous
difference between actual air pressure and
average air pressure at a given point.
sound pressure level The extent, in decibels, via
which SOUND PRESSURE exceeds 20 micropascals
(2.0 × 10 –5 pascal).
sound probe A transducer used to receive acoustic
vibrations for detection or measurement purposes.
sound recording The electrical recording of sound,
using cylinder, disc, tape, wire, or other comparable
storage medium.
sound-recording system A complete, integrated
array of equipment for recording sound, including
such components as microphones, amplifiers,
pickups, filters and other shaping networks,
attenuators, level indicators, and
recording mechanisms. Compare SOUND-
REPRODUCTION SYSTEM.
sound reinforcement Intensification of sound by
horns, resonant chambers, or other acoustical
devices.
sound relay See SOUND-OPERATED RELAY.
sound reproduction The electrical reproduction of
sound from recordings on vinyl discs, magnetic
tapes, magnetic discs, compact optical disbs, etc.
sound-reproduction system A complete, integrated
array of equipment for the playback of
recorded sound, including such components as
tape or record players, amplifiers, filters and
other shaping networks, attenuators, level indicators,
loudspeakers, and headphones. Compare
SOUND-RECORDING SYSTEM.
sound spectrograph A device that produces a display
of sound amplitude vs. frequency. Similar to
a SPECTRUM ANALYZER, except that it operates
at audio frequencies (about 20 Hz to 20 kHz) and
is actuated by acoustic disturbances, rather than
by electromagnetic signals.
sound spectrum The continuous band of frequencies
(about 20 Hz to 20 kHz) constituting
audible sounds, and sometimes the immediately
adjacent (subaudible and superaudible) frequencies.
sound stage The apparent dimensions of a sound
source.
sound survey meter A portable instrument for
measuring the intensity and other characteristics
of sound.
sound sweetening In audio recording or reproduction,
the modification of the sound to achieve
some desired effect.
sound system A sound-recording system, soundreproduction
system, or a combination of the two.
sound takeoff In a television receiver circuit, the
point at which the frequency-modulated sound
signal is extracted from the complex signal.
sound track The variable-density or variable-width
recording on one side of the film in sound-on-film
recording and reproduction. Also see OPTICAL
SOUND RECORDING.
sound transducer See ACOUSTIC TRANSDUCER.
sound-transmission coefficient See ACOUSTI-
CAL TRANSMITTIVITY.
sound trap In a television receiver circuit, a wavetrap
that prevents the sound signal from entering
the picture channels.
sound unit See PHONE, 2.
sound wave The vibratory phenomenon produced
in a medium by acoustic energy. A sound wave in
air consists of alternate compressions and rarefactions
of the air. Also see ACOUSTIC WAVE.
source 1. The origin of a signal or electrical energy
(e.g., a transmitting station). 2. In a field-effect
transistor, the electrode that is equivalent to the
emitter of a common-emitter-connected bipolar
transistor, or the cathode of a vacuum tube.
3. That which is being transcribed to magnetic
tape. 4. Manufacturer, wholesaler, or retailer.
source circuit 1. The circuit associated with the
source electrode of a field-effect transistor. 2. A
generator circuit. Compare SINK CIRCUIT.
source code See SOURCE LANGUAGE.
source computer A computer for compiling a
source program.
source-coupled multivibrator A multivibrator circuit
using field-effect transistors, in which feedback
coupling is achieved with a common source
resistor for the two FETs. This circuit is equivalent
to the emitter-coupled bipolar-transistortype
multivibrator.
source data automation A means of storing a
master data file for easy duplication, whenever
necessary.
source deck An audio or video tape player that reproduces
original recordings in the editing process.
source follower A field-effect-transistor circuit in
which the output is taken across a resistor between
source and ground. This circuit is equivalent
to the emitter follower, and is a unity-gain
stage whose impedance-transformation characteristics
make it ideal in signal conditioning,
buffering, and impedance-matching applications.
C in
+dc
Signal
input R g
R s
C out
Signal
output
source follower