Investigation of methods of secondary free-field calibration of working standard microphones

Project Description

This project is intended to investigate the viability of different methods of secondary free-field calibration and compare the results of these methods. It also addresses the need for a suitable sound source. The driver for this work is the preparation of the next part of the IEC 61094 series of Standards on measurement microphones, to describe methods of secondary free-field calibration of working standard microphones by comparison with laboratory standard microphones. The issues that will need to be covered by the project include:

  • Identification and investigation of a variety of alternative methods
  • Specification of the key requirements on the sound source used for these calibrations
  • Identification or development of suitable sources
  • The necessity for a free-field room or whether alternative methods based on signal processing and gated signals provide adequate results in an ordinary room

Where a free-field room is used, the specification of the minimum performance criteria for the room:

  • Investigation of the typical reproducibility between different laboratories with different types of free-field room (partly covered by P400)
  • A comparison of available sources to test if they are adequate or the design and development of suitable sound sources

Participation from Germany and Poland have to be confirmed.
Participation from Poland would be by organisation other than the NMI.The project was agreed at the TC-AUV meeting in May-04,

Final Report 2013-05-20

The project has been completed and the results contributed to the development of IEC 61094-8.

Progress Report 2005-08-12

A draft protocol was discussed at the sound-in-air SC meeting in Torino, May-05. Agreement was reached to split the project into two.The elements dealing with the performance of free-field rooms were deemed to make the overall project too large and will be considered separately at a later date, once 792 makes some progress. A revised protocol and timescale is in preparation.

NMI, NL ceased to be involved in airborne acoustics in 2005 and therefore withdrew from this project.

Acoustics, Ultrasound and Vibration (AUV)
Richard Barham, NPL (United Kingdom)
Coordinating Institute
NPL (United Kingdom)
Further Partners
DPLA (Denmark)