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Methods of free-field calibration of working standard microphones by comparison techniques: Euromat project 400.

Hanes, P (2000) Methods of free-field calibration of working standard microphones by comparison techniques: Euromat project 400. NPL Report. CMAM 57

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Abstract

The majority of acoustical measurements are made in free-field conditions using working standard microphones. Working standard microphones are not necessarily able to be calibrated by reciprocity techniques, and their calibration must therefore be achieved by another technique. The technique of free-field calibration by comparison with a calibrated reference microphone will be standardised as part of the IEC 61094 series. In order to assist in the preparation of the new Standard, a Euromet project was undertaken to gather information on comparison methods of free-field calibration. After a period of development, the four participating laboratories carried out an intercomparison exercise involving calibration of working standard microphones.
The exercise found agreement between the results of all four participants better than 0.12 dB at frequencies up to and including 2 kHz, and better than 0.5 dB at higher frequencies. The expanded uncertainties of measurement quoted by the laboratories were sufficient to explain all the between-laboratory differences. The influences of experimental arrangements, environmental conditions, free-field corrections for laboratory standard microphones and performance of the anechoic chambers on the results are discussed. Several issues are identified by the participants as requiring further examination in the course of preparing the new Standard.

Item Type: Report/Guide (NPL Report)
NPL Report No.: CMAM 57
Subjects: Acoustics
Acoustics > Sound in Air
Last Modified: 02 Feb 2018 13:17
URI: http://eprintspublications.npl.co.uk/id/eprint/1806

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