SC-04-04 meeting, Berlin, 2017-05

Report of the Meeting of the SC-04-04 working group on microphone measurement and characterization of the SC-04 subcommittee on acoustics, held in Berlin 2017-05-22

The meeting was convened by chair Jürgen Breitlow.

The introductions of attendees were made and the agenda was approved. The report of the previous meeting, held in Los Angeles was approved as written.

Open projects

AES42-R Review of AES42-2010: AES Standard for Acoustics - Digital interface for microphones
No new requirements for maintenance have been identified for AES42, it is reaffirmed in a new printing, 2016-02-08.

Development projects

AES-X085 Detailed Professional Microphone Specifications
IEC 60268-4 maintenance:
Maintenance has started. David Josephson is taking part for AES. Jürgen Breitlow is managing the project. A committee draft has been circulated and comments are expected.
Changes were:
1. For pop measurements the Sennheiser procedure was replaced by the IRT procedure which had been in annex before. The characteristics to be specified was changed to an equivalent SPL.
2. The QP noise measurement Matlab code provided by Hans Riekehof is now part of the CD as a new Annex D
3. The term “far-field microphone” is described but was never used before. It is now used rated conditions. There has been discussions to remove the term “far field microphone” from the standard which needs to be decided until the CDV. This issue was discussed in detail without a consensus or a recommendation for the maintenance team.

Wind measurements:
The wind round robin has not yet started. The microphones are ready in Berlin. The idea was to have one anemometer going with the microphones to have comparable wind speed measurements. Neumann will buy an anemometer and make it part of the round robin.

To summarize the measurement conditions: The wind round robin will be done with three microphones (DPA condenser cardioid and omni (4011 and 2006) and Sennheiser dynamic microphone (e835)). Tests will be done with and without simple wind shields. All tests should be recorded with 96kHz and 24bit for later comparison. For the measurements we agreed on the following list: frequency response (without wind), wind noise at 5m/s, 7m/s and 10m/s if possible.
All wind noise measurements should be recorded with 24bit@96kHz for later cross checks. C and A weighting should be applied to the measurements. The group agreed that A weighting is not appropriate but should be included because it is in the standard so far. Spectra should be measured and start at 5 Hz.
Participants so far are: Neumann/Sennheiser, Schoeps, Microtech Gefell, DPA, Beyer, Rycote, Josephson, AT and Shure. The microphones have been shipped to Neumann where we start with the round robin. The goal is to do the measurements within a month and forward them to the next.
Pop measurements should be done with all three microphones if a pop measurement setup is available at participants facilities to gain better understanding (see maintenance of IEC 60268-4 below).

It was suggested to do scan the wind speed profile during the test. 8 to 10 points in each direction should be a good resolution.

With the results from round robin the IEC 60268-4 wind part may be optimized in the next maintenance cycle.

Quasi peak algorithm: There has been a comment on a sample rate issue with the current code which will be reviewed by Hans. There is now a corrected version uploaded to the committee document site.

The Task Group SC-04-04-F was setup. There is a suggestion from Jeff Berryman and the AES70 maintenance group (X230-Mic-Profile-170216.xlsm) which is uploaded to AES website and waiting for comments from the sub-group.
The profile definition is quite clear for wired microphones but still need work for wireless mics.


MT IEC 61938:
CDV has been published. The only change was that impedance measurements are now extended to 200 kHz. All microphone interfacing was left untouched.

New projects:

A new project proposal has been initiated for a parameter tree for remote control of microphones in networks, to be maintained in SC-04-04 and supplied to SC-02-12-M and SC-07-01. Breitlow has posted the current status of this discussion.

New business:

There was no new business.

The next meeting will be held in New York, NY, USA 2017-10, in conjunction with the AES 143rd convention.

AES - Audio Engineering Society