BS EN 60118-15:2012 pdf download
BS EN 60118-15:2012 pdf download.Electroacoustics ——Hearing aids Part 15: Methods for characterising signal processing in hearing aids with aspeech-like signal.
a) The test box used shall provide essentially free field conditions In the frequency range 200 Hz to 8 kHz.
b) The hearing aid shall be positioned to reflect a frontal sound incidence (0 degrees azimuth and elevation as defined in IEC 61669). If this is not appropriate for the type of hearing aid, the actual incidence should be stated.
C) The input sound pressure level at the hearing aid reference point is kept constant by means of a reference microphone (pressure method) or by using the substitution method
d) One-third-octave-band filters with nominal centre frequencies from 250 Hz to 6,3 kHz shall be used The filters shall conform to the class 2 requirements of IEC 61260.
e) Unwanted stimuli in the acoustic test box, such as ambient noise and mechanical vibrations shall be sufficiently low so as not to affect the test results by more than 0,5 dB This can be verified if the output level of the hearing aid falls at least 10 dB when the signal source is switched otf.
1) The sound pressure level at the hearing aid reference point shall be accurate within
± 1,5 dB over the frequency range from 200 Hz 102 kHz and within ± 2,5 dB from 2 kHz to
8 kHz.
g) The free-field response level of the reference microphone used to measure the test signal, along with its associated amplifier and readout device, shall be frequency independent within ± 1 dB In the frequency range 200 Hz to 5 kHz and within ± 2 dB In the frequency range 5 kHz to 8 kHz relative to the free-field response level at 1 kHz. The pressure response level calibration of the reference microphone system shall be known by calibration at one frequency between 250 Hz and 1 250 Hz, preferably at 1 kHz. The expanded uncertainty of the calibration shall not exceed 1 dB.
h) The relative pressure response level of the coupler microphone, along with its associated amplifier and readout device, shall be frequency-independent within ± 1 dB in the frequency range 200 Hz to 5 kHz and within ± 2 dB in the range 5 kHz to 8 kHz relative to the pressure sensitivity at 1 kt-Iz. The pressure response level calibration of the coupler microphone system shall be known by calibration at one frequency between 250 Hz and 1 250 Hz. preferably at 1 kHz. The expanded uncertainty of the calibration shall not exceed 1 dB.
62 Test signal
6.2.1 Specification of ISTS
The international speech lest signal (ISTS) shall be used as the test signal for the measurements of this standard. This signal is developed by the European Hearing Instrument Manufacturers Association which holds the copyright. It is available from this organization free of charge as a 16 bit or 24 bit file of type way.
The ISTS has been produced from recordings of female speakers of Arabic. English. French.
German. Mandarin and Spanish. The recordings were cut into short segments and
recomposed In random order. A description of the ISTS is given in Annex A and In liii. The
ISTS has the Following essential characteristics:
a) The signal bandwidth is from 100 Hz to 16 kHz. For the measurements in this standard only the bandwidth is relevant that includes all one-third-octave bands with nominal centre frequencies from 0,25 kHz to 6,3 kl-tz,
b) The long term average speech spectrum (LTASS) is given in Table I and in Figure 3. It Is the average LTASS for female talkers reported in [21. For acoustical reproduction the accuracy shall be within ± 3 dB for all one-third-octave bands with nominal centre frequencies from 0,25 kHz to 6,3 khz,
C) The 30th, 65ih and 99th percentiles of the distribution of the sound pressure level in 125 ms time blocks In one-third-octave-octave bands are given In Table 1 and in Figure 3.For acoustical reproduction the accuracy shall be within ± 3 dB for all one-third-octave bands with nominal centre frequencies from 0,25 kHz to 6,3 kHz.
