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RIAA: RIAA equalization is a specification for the correct playback of vinyl records, established by the
Recording Industry Association of America (RIAA). The purpose of the equalization is to permit greater
playback times, improve sound quality, and to limit the physical extremes that would otherwise arise
from recording analogue records without such equalization. A record is cut with the low frequencies
reduced and the high frequencies boosted, and on playback the opposite occurs. The result is a flat
frequency response.
Sample: In music, sampling is the act of taking a portion, or sample, of one sound recording and
reusing it as an instrument or element of a new recording. This is typically done with a sampler, which
can be a piece of hardware or a computer program.
In signal processing, sampling is the reduction of a continuous signal to a discrete signal. Sampling
picks out samples from a continious signal at a certain frequency. When it is necessary to capture audio
covering the entire 20-20kHz range, such as when recording music, audio waveforms are typically
sampled at 44.1kHz (CD) or 48 kHz (professional audio).
Sound: Sound can be perceived by the sense of hearing. By sound, we commonly mean the vibrations
that travel through air and are audible to people. Humans and many animals use their ears to hear
sound, but loud sounds and low-frequency sounds can be perceived as vibrations by other parts of the
body via the sense of touch. Sound propagates as waves of alternating pressure, causing local regions
of compression and rarefaction.
S/P DIF: Abbreviation for Sony / Philips digital interconnect format. It specifies a protocol for carrying
digital audio signals between devices.
Stereo: Stereophonic sound is the reproduction of sound, using two independent audio channels.
Stereophonic sound attempts to create an illusion of location for various instruments within the original
recording.
Subsonic signal: This is an audio signal with frequency below 20Hz. This signal is not audible, it only
creates air movement that can be felt.
SUM signal: This signal is the proportional summation (mix) of all input signals. Also called main mix
signal.
Symmetrical (synonym: balanced): A balanced line or balanced signal pair is a transmission line
consisting of two conductors of the same type, and equal impedance to ground and other circuits.
Balanced lines are operated with differential signals, one of which is the inverse of the other. Balanced
lines reduce the amount of noise per distance, allowing a longer cable run to be practical. This is
because electromagnetic interference will affect both signals the same way. Similarities between the
two signals are automatically removed at the end of the transmission path when one signal is
subtracted from the other.
Talk-over (synonym: voice-over, ducker): It is an effect where the level of one signal is reduced by the
presence of another signal, through the use of side chain compression. A typical application is to
automatically lower the level of the musical background when a talk-over starts, and to automatically
bring the level up again when the talk-over stops.
THD: Abbreviation of Total Harmonic Distortion. When a signal passes through a non-linear device,
additional content is added at the harmonics of the original frequencies. THD is a measurement of the
extent of that distortion.
USB: Abbreviation for Universal Serial Bus. It is a serial bus standard to transport data between (mostly
computer related) devices.