ISO 8253-2-2009 pdf free download

ISO 8253-2-2009 pdf free download.Acoustics — Audiometric test methods — Part 2:Sound field audiometry with pure-tone and narrow-band test signals
Acoustique — Méthodes d’essais audiomOtriques — Partie 2: Audiométrie en champ acoustique avec des sons purs et des bruits a bande étroite comme signaux d’essai.
Sound pressure level measurements shall be made with a sound level meter complying with IEC 61672-1. type 1. with the exception of the measurements using a directional microphone given in 5.3.
The signals for testing the sound field shall be the same as those used for audiometry.
5.2 Free sound field
To establish that free sound field conditions are adequately met, the following requirements shall be complied with.
a) The loudspeaker shall be arranged at the head height of a seated listener, the reference axis being directed through the reference point. The distance between the reference point and the loudspeaker shall be at least I m.
b) With the test subject and the subject’s chair absent, the sound pressure level produced by the loudspeaker at positions 0,15 m from the reference point on the left-right and up-down axis shall deviate by no more than ± 1 dB from the sound pressure level at the reference point for any of the test frequencies up to and including 4 000 Hz. and by no more than ± 2 dB for any of the test signals at frequencies above 4 000 Hz. The difference in sound pressure levels between the left-right positions shall not exceed 3 dB at any frequency above 4 000 Hz.
c) With the test subject and the subjects chair absent, the difference in sound pressure levels produced by the loudspeaker at points on the reference axis 0,15 m in front of and 0.15 m behind the reference point shall deviate from the theoretical value given by the inverse sound pressure distance law by no more than ± 1 dB for any of the test signals.
NOTE These requirements can only be met In an anechoic room.
5.3 Diffuse sound field
To establish that diffuse sound field conditions are adequately met, the following requirements shall be complied with.
a) With the test subject and the subject’s chair absent, the sound pressure level measured with an omnidirectional microphone at positions 0,15 m from the reference point on the front-back, right-left and up-down axes shall deviate by no more than ± 2,5 dB from the sound pressure level at the reference point for any of the test signals. Furthermore, the difference between levels for the extreme right-left positions shall not exceed 3 dB. The orientation of the microphone shall be kept the same at each position.
b) At frequencies of 500 Hz and above, the sound pressure levels at the reference point shall be within 5 dB for the two directions of measurement that give maximum and minimum readings of the incident sound energy when measured with a directional microphone with a front-to-random sensitivity index of 5 dB. For other directional microphones, the relationship between front-to-random sensitivity index and the allowable field variation is given in Table 1.ISO 8253-2-2009 pdf free download.