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User's Guide Version 3.4 © June 2011
RM500SL
®
short-term spectra are typically 120 - 130 millisecond averages in 1/3 octaves. The
statistical range is typically from the 70th to the 99th percentile.
SPL, Sound Pressure Level, rms sound pressure relative to 20 uPa, expressed in decibels.
SPL = 20log10 (rms sound pressure / 20uPa).
SPLITS, coupler SPL for an inductive telephone simulator, SPL developed in a 2cc
coupler by a hearing aid with the gain control at the RTS when the input is the magnetic
field generated by a TMFS (ANSI S3.22).
TMFS, Telephone magnetic-field simulator, a device for producing a magnetic field of
consistent level and geometric shape when driven by a specified current (ANSI S3.22).
THD, Total Harmonic Distortion, the power in all harmonic components as a percentage
of the power in the fundamental. If less than 20%, the power of the total signal may be used
instead of the fundamental. For most hearing aids, the inclusion of harmonics above the
third will not significantly alter the THD (ANSI S3.22).
Transducer, a device which transforms energy from one form to another. For example, a
microphone or earphone.
UCL, Uncomfortable Listening Level, the level for a specified stimulus that is judged to
be definitely uncomfortable.
VGA, video graphics adapter.
VC, Volume Control, a user-operated gain control.
Warble Tone, a frequency-modulated sine wave. The modulating signal is often a low
frequency triangle wave.
1. Valente, M: Strategies for Selecting and Verifying Hearing Aid Fittings. New
York:Thieme Medical Publishers, Inc.,1994.
ANSI S3.5, Methods for Calculation of the Speech Intelligibility Index, 1997
ANSI S3.6, Specification for Audiometers, 1996
ANSI S3.22, Specification of Hearing Aid Characteristics, revised 2003.
ANSI S3.46, Methods of Measurement of Real-Ear Performance Characteristics of Hearing
Aids, 1997.
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