octave:
An interval between two frequencies,
the higher of which is twice that of the
lower; in modern music, an octave is
eight notes of the scale.
passband:
The continuous spectrum of frequen-
cies transmitted by a filter, amplifier, or
similar device.
signal-to-noise ratio:
The specification which indicates how
much audio signal there is relative to
the noise under specified conditions. It
is the ratio of total audio output level to
the noise level expressed in dB.
slope:
The rate at which a crossover attenuates
out-of-band frequencies. Expressed in
dB per octave, typical slopes are 6, 12,
and 18 per octave, with 12 being the
most common; the higher the number,
the faster attenuation occurs relative to
frequency.
sound pressure level
A measurement of acoustic energy
(SPL):
expressed in dB.
total harmonic
distortion (THD):
The percentage of an audio output sig-
nal that consists of spurious harmonics,
or multiples of the fundamental fre-
quencies. These harmonics are intro-
duced by a power amplifier or other
component through which the signal
passes; lower figures are better.
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