GB/T 4854.7-2008: Acoustics -- Reference zero for the calibration of audiometric equipment -- Part 7: Reference threshold of hearing under free-field and diffuse-field listening conditions

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Scope

This Part specifies a reference threshold of hearing for the calibration of audiometric
equipment used under the following conditions.
a) The sound field in the absence of the listener consists of either a free
progressive plane wave (free field) or a diffuse sound field. In the case of a
free field, the source of sound is directly in front of the listener (frontal
incidence).
b) The sound signals are pure (sinusoidal) tones in the case of free-field
conditions and one-third octave bands of (white or pink) noise in the case of
diffuse-field conditions.
c) The sound pressure level is measured in the absence of the listener at the
position where the center of the listener’s head would be.
d) Listening is binaural.
NOTE 1: correction values for the threshold of hearing under free-field listening
conditions and selected angles of sound incidence (45° and 90°) deviating
from frontal incidence are given in GB/T 16296 for information.
NOTE 2: other conditions are given in Bibliographic Reference [1].
The data are given in Table 1, in numerical form for the preferred frequencies in the
one-third-octave series from 20 Hz to 16 kHz inclusive in accordance with GB/T 3240
and, in addition, for some intermediate audiometric frequencies up to 18 kHz.
It should be emphasized that the threshold data differ from the audiometric zero
specified in GB/T 4854.1 and GB/T 16402, since the latter refer to monaural listening
through earphones with sound pressure levels referred to specified couplers and ear
simulators. Direct comparison between the data in this Part, and GB/T 4854.1 or GB/T
16402 is therefore not appropriate.

Basic Data

Standard ID	GB/T 4854.7-2008 (GB/T4854.7-2008)
Description (Translated English)	Acoustics -- Reference zero for the calibration of audiometric equipment -- Part 7: Reference threshold of hearing under free-field and diffuse-field listening conditions
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	A59
Classification of International Standard	17.140
Word Count Estimation	13,192
Date of Issue	2008-07-02
Date of Implementation	2009-02-01
Older Standard (superseded by this standard)	GB/T 4854.7-1999
Adopted Standard	ISO 389-7-2005, IDT
Regulation (derived from)	Announcement of Newly Approved National Standards No. 11 of 2008 (No. 124 overall)
Issuing agency(ies)	General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China, Standardization Administration of the People's Republic of China
Summary	This standard specifies the following conditions of use in the calibration of audiometric equipment Reference threshold of hearing. A) subjects were not present when the sound field from a free plane traveling wave field (free field) or a diffuse field composition. Free field conditions, subjects should face the sound source (prior to the incident). B) free-field conditions, the acoustic signal should be pure (sinusoidal) tones, diffuse field conditions, compared with 1/3 octave band white noise or pink noise. C) sound pressure level measurements shall be subject in absence of head center position (ears, external ear canal midpoint) proceed. D) binaural audiometry.