AES Journal Forum Comments

AES Journal Forum: Comment by Alvin A. Reid on "Virtual Localization by Blind Persons"

Wed, 26 Sep 2012 10:55:46 -0600

Title: Virtual Localization by Blind Persons
JAES Volume 60 Issue 7/8 pp. 568-579; July 2012
Comment by: Alvin A. Reid

I'd like to see some elaboration on congenital blindness or blindness since birth vs age related degeneration and traumatic injury to the ocular system. Since the visual cortex probably never develops in the latter case those individuals may hear bands of frequencies not normally visited by sighted individuals. Dr. Wersenyi didn't mention this in the paper and was conspicuously absent in touching on these areas.

AES Journal Forum: Comment by Alvin A. Reid on "Effect of Spatial Location and Presentation Rate on the Reaction to Auditory Displays"

Tue, 04 Sep 2012 10:17:00 -0600

Title: Effect of Spatial Location and Presentation Rate on the Reaction to Auditory Displays
JAES Volume 60 Issue 7/8 pp. 497-504; July 2012
Comment by: Alvin A. Reid

Dr. Roginska: Thanks for the refreshing updates. I'm curious about the digit assignments and can they be morphed and or stretched over a period of time and still be effectively retained as a cognitive memory trace?

AES Journal Forum: Comment by Arijit Biswas on "Watermark-Aided Pre-Echo Reduction in Low Bit-Rate Audio Coding"

Wed, 15 Aug 2012 13:38:59 -0600

Title: Watermark-Aided Pre-Echo Reduction in Low Bit-Rate Audio Coding
JAES Volume 60 Issue 6 pp. 431-443; June 2012
Comment by: Arijit Biswas

Very interesting paper and it was very nice to read.

However, I’ve got one question/comment:
Authors mention that “ARMA model is used to estimate the temporal envelope”.

I agree with the authors that ARMA model is efficient, but how does the authors guarantee stability of the ARMA model? I’m concerned because ARMA modeling using Prony’s Method is not guaranteed to be stable. See this link: http://www.mathworks.co.uk/help/toolbox/signal/ug/f11-7042.html
In case you have some references or used some techniques to guarantee the stability of the ARMA modeling using Prony (or any other method), I would be very interested to know.

Best Regards,
Arijit

AES Journal Forum: Comment by Christopher Dion on "Digital Dynamic Range Compressor Design—A Tutorial and Analysis"

Sat, 04 Aug 2012 09:59:11 -0600

Title: Digital Dynamic Range Compressor Design—A Tutorial and Analysis
JAES Volume 60 Issue 6 pp. 399-408; June 2012
Comment by: Christopher Dion

Thank you for your comprehensive answer. It is very well appreciated. Good work.

Chris

AES Journal Forum: Comment by Joshua Reiss on "Digital Dynamic Range Compressor Design—A Tutorial and Analysis"

Thu, 02 Aug 2012 10:09:41 -0600

Title: Digital Dynamic Range Compressor Design—A Tutorial and Analysis
JAES Volume 60 Issue 6 pp. 399-408; June 2012
Comment by: Joshua Reiss

Thanks for your comments.

I'm aware of this paper, and in fact cited the revised and extended version,

F. Floru, “Attack and Release Time Constants in RMS-Based Feedback Compressors,” vol. 47, pp. 788–804 (1999 Oct.).

But if all other aspects are equal, then applying attack and release on a linear estimation of input signal level clearly gives different results from applying them on a logarithmic estimation of signal level (or on the logarithmic gain). This is seen in Fig. 11 and Table 1 of our paper, and commented on in Sonnox, “Dynamics Plug-In Manual,” Sonnox Oxford Plug-ins, April 1st 2007.

You can also clearly see the difference between Eq.s 20 and 23 in our paper.

I think there are a few reasons why Floru's result, though very interesting and significant, does not apply;

- He has slightly different definitions of log and linear domain

- He deals only with RMS detectors, and in fact requires that the RMS detection be log domain when applying attack and release in log domain, and be linear when applying attack and release in linear domain

- Technically, transfer function does not apply, since it assumes a linear system. The output of a compressor is, of course, dependent on signal level as well as frequency. Describing functions may be more appropriate, since they describe nonlinear relationships where the input/output relationship is a function of both frequency and amplitude. But even they assume a static nonlinearity, and thus really only model clipping or hard limiters.

Of course, Floru's paper(s) on the subject are very detailed and fairly complex, so without a thorough reading, I can't say for sure why he got that result and what the implications are.

Best regards,

Josh