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

Foreword

GB/T 4854 Acoustics - Reference Zero for the Calibration of Audiometric Equipment

includes eight parts:

---GB/T 4854.1 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 1: Reference Equivalent Threshold Sound Pressure Levels

for Pure Tones and Supra-aural Earphones

---GB/T 16402 Acoustics - Reference Equivalent Threshold Sound Pressure

Levels for Pure Tones and Insert Earphones

---GB/T 4854.3 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 3: Reference Equivalent Threshold Force Levels for Pure

Tones and Bone Vibrators

---GB/T 4854.4 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 4: Reference Levels for Narrow-band Masking Noise

---GB/T 4854.5 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 5: Reference Equivalent Threshold Sound Pressure Levels

for Pure Tones in the Frequency Range 8 kHz to 16 kHz

---GB/T 4854.6 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 6: Reference Hearing Threshold Levels for Test Signals of

Short Duration

---GB/T 4854.7 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 7: Reference Threshold of Hearing under Free-field and

Diffuse-field Listening Conditions

---GB/T 4854.8 Acoustics - Reference Zero for the Calibration of Audiometric

Equipment - Part 8: Reference Equivalent Threshold Sound Pressure Levels

for Pure Tone and Circum-aural Earphones

NOTE: when the 2nd part in the series was formulated, the serial No. was GB/T 16402.

At that time, the series standards has not yet been established. This Part will

be modified into GB/T 4854.2 in the subsequent revision.

This is Part 7 of GB/T 4854.

This Part equivalently adopts ISO 389-7:2005 Acoustics - Reference Zero for the

Calibration of Audiometric Equipment - Part 7: Reference Threshold of Hearing under

Free-field and Diffuse-field Listening Conditions. This Part serves as a replacement of

GB/T 4854.7-1999. In comparison with the previous edition, this Part introduces the

newly published research achievements since 1996. Therefore, the free-field and

Acoustics - Reference Zero for the Calibration of

Audiometric Equipment - Part 7: Reference Threshold

of Hearing under Free-field and Diffuse-field Listening

Conditions

1 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.

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