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SC-02-01 meeting, Online, 2021-05

Report of the meeting of the SC-02-01 Working Group on Digital audio measurement techniques, held online, 2021-10-04.

The meeting was convened by vice-chair I. G. Dennis.

The report of the previous meeting, held online 2021-05-12, was approved as written.

The agenda was approved as written.

In attendence were Richard Cabot, Bruce Olson, Thomas Lago, Chris Lacinak, Ian Dennis, Paul Treleaven, Jan Axelsson, John Grant and Rebecca Chandler

Projects assigned to this group but not mentioned here had no action requested or required - see www.aes.org/standards/meetings/project-status.cfm for details.

Open Projects:

AES-X217 Audio ADC test method and performance specification for archiving and preservation applications
A task group (Richard Cabot, Ian Dennis, Chris Lacinak, Rebecca Chandler, Jayant Datta) has produced various drafts, mainly attempting to resolve discrepancies with existing standards. Most lately, Jayant Datta and Ian Dennis revised the draft and issue it to SC-02-01 for comment on 2021-09-17. No comments have been received as yet.

It was decided to work through the remaining queries in the latest draft in an effort to resolve them. Some detailed points were discussed.

Regarding the tables in Annex B:

  • In B.1, the bottom row should refer to the range from 20kHz to 40kHz
  • In other tables in Annex B, column headings are inconsistent, e.g. references to ‘Hz’ and ‘kHz’ in different columns. It was decided to standardise on ‘Hz’ and add suffixes such as ‘k’ in the column entries as required.
  • In tables B.6 and B.7 (intermodulation) various nomenclatures were revised.
  • It was agreed to add ‘Minimum’ to the heading of Annex B, to resolve Ian’s comment in the draft that the required performance levels were now somewhat below the state of the art.
  • There was general discussion about ‘dBFS’ vs ‘dB FS’. No conclusion was reached.

It was noted that nearly all of the remaining queries in the draft concern differences between the proposed methods and those described existing standards such as IEC61606-3, AES17 and IEC60268. Ian clarified that the sticking points are largely in deciding whether each queried method should be re-aligned with existing standards and described with reference to them (as per AES67), or allowed to remain different. The philosophy so far has been to align the methods where there is no good reason for them to be different. It was decided that this is a good approach, and to emphasise in the document that any remaining methods are unique (or at least different from the other standards).

Section 5.5.2. (CMRR) refers to a figure by Whitlock and references a random website which includes it. It was noted that the same figures are included in IEC60268, so we should refer to that instead (although the actual method in IEC60268 may be different).

Another deviation from other standards is the specified use of the ‘Rife Vincent 5’ FFT window in section 5.9. Chris confirmed that there was no reason for this, except that it was probably what happened to be in use when the example measurements were originally made. It was generally felt that a more ubiquitous window should be specified since ‘Rife Vincent 5’ is not generally available on most test equipment. Thomas said that he had been involved with developing optimal window functions, and Bruce asked him to recommend a window.

Bruce suggested that we submit the latest draft to SC-03-06 [Working Group on Digital Library and Archive Systems] and ask them to resolve the remaining queries. On reviewing of the draft, it was later decided that we should remove editorial and resolve questions within SC-02-01 before submitting to SC-03-06 for comment.

Liaisons

No new liaison information.

New projects

No new projects proposed.

New business

No new business proposed

The next meeting will be scheduled in conjunction with the AES 152nd Convention, to be held in May 2022.

AES - Audio Engineering Society