BS EN 61669 pdf free download
BS EN 61669 pdf free download. Electroacoustics — Measurement of real-ear acoustical performance characteristics of hearing aids.
6.3 Test signal The equipment manufacturer shall report the test signal type(s) provided by the equipment and shall supply the information listed below for each type. For hearing aids employing advanced signal processing techniques the International Speech Test Signal (ISTS) specified in IEC 601 1 8-1 5 should be used. For a pure-tone test signal, report the frequency spacing (if stepped) and total harmonic distortion. For a tone burst, report the frequency spacing (if stepped), the ON and OFF times for the burst, the number of repetitions at each frequency and the SPL during the ON time of the tone burst. For a warble tone test signal, report the frequency spacing (if stepped), modulating frequency, frequency deviation, and type of modulating waveform. For a narrow-band noise test signal, report the frequency spacing (if stepped), effective bandwidth, slope of band skirts, and the spacing of frequency components within the band (if pseudo-random). For a random noise test signal, report the crest factor and frequency spectrum employed. For pseudo-random noise, chirp, and click test signals, report the spacing and number of frequency components, lowest frequency present, frequency spectrum employed, repetition rate, and crest factor. For an MLS test signal, report order, sampling rate, crest factor, and frequency spectrum employed. For a speech-like test signal, report the test signal level and the bandwidth over which it is determined, the LTASS and, if digitized, the sampling rate and number of bits. If the test signal is standardized or commercially available, report the source and identifying information. The International Speech Test Signal (ISTS) specified in IEC 601 1 8-1 5 is the preferred speech-like test signal. If the speech has been modified by other than linear filtering, a description of the processing or a reference where it can be found should be provided. Measurements of real-ear acoustical performance characteristics of hearing aids which use non-linear or analytical processing techniques are valid only for the test signals and conditions employed. These measurements should be performed in accordance with the hearing aid manufacturer’s recommendations, as they can require specific test signals or test conditions outside the scope of this standard. 6.4 Sound field source When using the substitution method, the sound field source shall consist only of coaxial elements. In order to avoid reflections, the frontal surface of the sound field source enclosure shall be covered with a suitable absorbing material. When using the modified pressure method these restrictions do not apply. 6.5 Coupled sound source The magnitude of the acoustic impedance of the coupled sound source used in the measurement of the RECD shall be at least 3.1 6 times that of the occluded test ear and of the 2 cm 3 coupler. 6.6 Test signal range Narrow-band test signal levels shall cover the range from 50 dB to 90 dB at a working distance of 0,5 m in an anechoic environment, with a maximum step size of 5 dB. 6.7 Test signal level indication For the range of levels indicated by the equipment manufacturer, when measured at the inlet to the reference microphone, the indicated test signal level as a function of frequency shall be accurate within 4 dB. 6.8 Equalization In an anechoic environment, equalization shall allow the test signal to be controlled, as a function of frequency, to within 4 dB of the intended test signal level at the field reference point at a working distance of 0,5 m.BS EN 61669 pdf download.
