audioscan RM500SL User Manual page 104

User's Guide Version 3.4 © June 2011
RM500SL ®
transmitter and an fm receiver. The microphone and transmitter are worn by the speaker
and the receiver is worn by the listener.
FOG, full on gain, gain for a 50 dB input SPL with the gain control set to maximum ANSI
S3.22)
Gain (in dB), output sound pressure relative to input sound pressure, expressed in
decibels; gain = 20log10 (output sound pressure / input sound pressure); also, gain =
(output SPL) - (input SPL).
Gain control, a manually or electronically operated control for the adjustment of overall
gain (ANSI S3.22).
HA-1 Coupler, a coupler having a volume of 2 cubic centimetres with direct access to the
cavity. Used for testing in-the-ear and in-the-canal hearing aids; can also be used to test
behind-the-ear hearing aids with a custom earmold attached. Aka the ITE coupler.
HA-2 Coupler, a coupler having a volume of 2 cubic centimetres with access through a
rigid tube. When used for testing BTE hearing aids, the rigid tube consists of 18 mm of 3
mm tubing plus 25 mm of 2 mm tubing (ANSI S3.22). When used for calibrating insert
earphones, the 2 mm tubing is not used (ANSI S3.6). Aka the BTE coupler.
Harmonic, a component of a tone complex that is an integer multiple of the lowest
frequency component (fundamental).
Harmonic Distortion, the addition of harmonic components to a signal. The rms value of a
harmonic component of a signal as a percentage of the rms value of the fundamental. If less
than 20%, the rms value of the total signal may be used instead of the fundamental.
HFA, High Frequency Average, the average of values in dB at 1000, 1600, and 2500 Hz.
(ANSI S3.22).
HL, Hearing Level, the hearing threshold referenced to the threshold of normal hearing,
expressed in dB.
HI, Hearing instrument.
Input Compression, a form of AGC in which the signal level is regulated before the
volume control.
Input / Output function, steady state, single-frequency plot of the coupler SPL on the
ordinate as a function of input SPL on the abscissa with equal decibel scale divisions on
each axis (ANSI S3.22).
ITE, In-The-Ear (hearing aid).
Kneepoint (compression threshold), the point on an input/output curve at which the slope
digresses from unity indicating the signal level at which a non-linear process begins to take
effect.1
LCD, liquid crystal display. A thin, planar information display.
Linear Region, that portion of the input-output function which is a straight line at 45
degrees.
Linear Amplification, amplification having the same gain for all input levels until the
maximum output of the device is reached.
LTASS, Long-term average speech spectrum, the rms level of a speech passage in
1/3rd octave bands, averaged over the entire passage.
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