MedRx AVANT REM (Real Ear Measurement) Installation Manual
Effective Date: 05-25-2017
16
Stimulus Signal Types
Pure Tone
A pure sine wave. Crest Factor = 1.41 (3.0dB)
Broadband Noise (BBN)
Uniform random noise with normal (Gaussian) amplitude distribution. Can be weighted to
White, Pink, Speech ANSI, and Speech Byrne (see below.)
Pseudo Random Noise (PRN)
A "synthetic" broadband random noise. It is less uniform than BBN, has lower spectral density
and random volleys. Can be weigted to White, Pink, Speech ANSI, and Speech Byrne (see
below.)
ICRA Noise
This stimulus was developed for measuring characteristics of non-linear instruments. The
noise is weighted to Byrne LTASS.
ISTS
(International Speech Test Signal)
Initiated by European Hearing Instrument Manufacturing Association (EHIMA.) This signal is
based on natural recordings of 21 female speakers in six different languages - American
English, Arabic, Chinese, French, German and Spanish. The signal is largely non-intelligible
because of segmentation and remixing. The speech material was filtered to Byrne LTASS.
Crest Factor: 9.23 (19.3dB)
Rainbow Passage
Natural recordings of several voices reciting the rainbow passage. Shaped to Byrne LTASS.
Broadband Noise Weighting
White
This is essentially no weighting or filtering. The White Noise has flat power spectral density.
Power at every frequency is equal. Because the density of frequencies (individual cycles) raises
with frequency, there is more energy in high octaves.
White-weighted noise can be used mostly for testing of equipment. It is not recommended to
use it for hearing aid fitting, unless specified by the manufacturer.
Crest Factor: BBN = 1.73 (4.8dB), PRN = 7.86 (17.9dB)
