Comments to date on DRAFT AES56-xxxx, AES standard on acoustics - Sound source modeling - Loudspeaker polar radiation measurements, published 2008-09-11 for comment.
The comment period has now closed. There are no unresolved comments.
Comment received from Christopher J. Struck - CJS Labs, San Francisco, 2008-12-10
4.1.1 The terms "small devices" and "large devices" are ambiguous and
undefined. Recommend replacing the last sentence with "The minimum
measurement distance shall be at least 3 times the maximum linear dimension
of the source, including the enclosure."
In addition, I could find no reference within the text of this document with
respect to the Conditions of the Measurement, i.e., Free Field, half space,
4p, quasi anechoic (gated/simulated free field), etc. I recommend a sentence
to this effect be added to 4.1, preferably before 4.1.1,
Respectfully submitted,
Christopher J. Struck
Response from Wolfgang Ahnert, Chair SC-04-01, 2009-01-16
1. A complete discussion of measurement methods of real-world boxes would
be a substantial tutorial document, however this standard on angular
measurements is not the intended place for that discussion. Specifically,
the consideration of measurement distance is not intended to be part of this
standard. However, we understand that it is important that naive users
should not interpret the provision in 4.1.1 (that normalizes reporting at 1
m) as sanctioning measurements at 1 m. This was the intent in the existing
text but we agree it could be interpreted ambiguously. Accordingly, we
propose that the text in 4.1.1, "The measurement distance ... annex A.1",
should be replaced by the following Note as an editorial matter.
"NOTE Consideration of actual measurement distances for individual
loudspeakers is not covered in this standard, however practical measurements
will seek to reduce phase errors in complex data by ensuring that the
measurement distance is large compared to the dimensions of the loudspeaker.
Typically, the measurement distance would be a minimum value of 4 m or, more
typically, 8 m. See also annex A.1."
2. Many issues of practical measurement are not considered in this standard
on measurement angles, although they would, of course, be relevant for a
complete measurement protocol. The consideration of conditions of
measurement is currently outside the scope of this standard.
Please let me know as soon as possible if this response is not acceptable to
you. You may also ask us to consider your comments again for the next
revision of the document. You may also appeal this decision to the
Standards Secretariat.
Response from Christopher J. Struck, 2009-01-16
What you have proposed is excellent and covers the issue quite
elegantly.
