SC-04-04 meeting, San Francisco, 2010-11

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 San Francisco, 2010-11-06

The meeting was convened by chair David Josephson.

The agenda were approved. There had been no meeting at the 128th AES convention in London.

Open Projects

AES42-R Review of AES42-2006: AES Standard for Acoustics - Digital interface for microphones
Task group SC-04-04-D had completed its revision cycle and its proposed revision (PTD) of AES42-2006 was posted on the document site with notice on the SC-04-04 reflector on 2010-09-20. No comment has been received and the Standards Secretary was asked to prepare a formatted copy for release as a call for comment. The SC-04-04 working group sincerely thanks Christian Langen and the team in SC-04-04-D for their excellent work in deriving consensus on a complex and important standard for digitally-interfaced microphones.

Development Projects

AES-X085 Detailed Professional Microphone Specifications
The chair gave a report on the progress of AES-X085. The round-robin test of the noise source provided by DPA had been stalled for more than a year as one working group member was unable to complete the required tests. The noise source was retrieved and is on its way to S. Temme of Listen, Inc for the last round of tests in this effort. S. Peus indicated his disappointment in the inability of participants in this effort to reach consistent results in performing these tests. The chair will attempt to lead a discussion on the email reflector on this topic to see whether a more uniform approach can be adopted by more companies.

Also in AES-X085, there was extended discussion of the possibility of moving forward with the concept of a detailed datasheet format for professional users, that has been the goal of this project for the past twelve years. A few working-group members have submitted proposals for such a format but opinion seems to be divided as to the necessity of such a standard. There is still no measurement method for directional microphones at low frequencies that can be accepted by all participating companies. IEC 60268-4 permits a wide variety of testing methods which seldom produce comparable results. The concept of defining several test protocols, each of them within the requirements of IEC 60268-4 but more specific as to intended application of the microphone under test, was discussed and the chair plans to post a selection of possible methods for discussion on the reflector.

The chair reported that the working group's recommendations for the revision of IEC 60268-4 had been accepted by the IEC maintenance team for this standard for the inclusion in the next revision of this standard. A new revision cycle of this standard is scheduled to begin in 2011 and the working group should be prepared to suggest further refinements now that the working-group chair is now a member of the maintenance team for IEC 60268-4 through the D-liaison with AES.

In general the work on AES-X085 is focusing on defining more specific procedures which can be agreed upon, within the generally broad IEC standards, to produce measurements from different manufacturers that are more closely comparable with each other.

AES-X093 Recommendations for revisions of IEC 61938 clause 7, Phantom power
The chair reported that, since the last meeting, he had also joined the maintenance team for IEC 61938, and all of the working group's comments and suggestions for the revision of the phantom power standard had been accepted by the MT for inclusion in the revision now in process. This revision has passed its comment period and is expected to be published in the spring of 2011. The meeting therefore asked the AESSC Secretary therefore to retire AES-X093 on the publication of IEC 61937 Ed.2 as its work is complete.

AES-X189 Connector for surround microphones
Work continues on the project AES-X189. The chair reported that, as anticipated, the connector previously discussed has been included in the upcoming standard IEC 61076-2-106. There had been some concern that the 19-pin variant might not be included in the standard, but a copy of 48B/2063/CDV was reviewed to show that the 19-pin variant was indeed present. It is expected that this standard will progress as anticipated. The chair will write a report incorporating the recommendation previously adopted by SC-04-04 for action by SC-05-02 in progressing this to a standard for this interface. The chair noted that two of the six microphones presented at the workshop on single-point-surround pickups at this Convention used a cable intended to complement the proposed standard developed in this project.

New projects

No new projects were proposed. There was no further discussion on the proposed project for the characterization of wireless microphone systems.

New business

There was no new business.

The date of the next meeting was noted to be in conjunction with the 131st Convention of the AES in New York, 2011-11. There was no discussion of this topic, but there may also be a meeting at the 130th Convention in London, 2011-05.

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