Dear surround list, I could try to clarify a bit our recording and reproduction method, described in the Physics Today article:
We do recordings via impulse responses, meaning that we capture spatial impulse responses in the concert halls and convolve the anechoic music afterwards. This process is to done to get better spatial sound quality in the lab. Earlier we used Spatial Impulse Response Rendering (SIRR) method: http://www.acoustics.hut.fi/research/cat/sirr/ Our current system use a method, called Spatial Decomposition Method (SDM), which is published in Journal of the AES: http://www.aes.org/e-lib/browse.cfm?elib=16664, see also: https://mediatech.aalto.fi/en/research/virtual-acoustics/research/acoustic-measurement-and-analysis/82-sdm The SDM is a parametric method that differs significantly from spherical harmonics based methods. It requires at least 4 omni mics (we use 6) and the basic idea is as follows. An impulse response is analyzed with a short time window and cross-correlations between mic pairs are computed to obtain a time-difference-of-arrival (TDOA) in each pair. With 6 mice you get 15 TDOA estimates. From these time differences it can be estimated from which direction the sound energy is reaching the microphone array. Such analysis is done for every single sample (i.e. a short time window, 1ms, is shifted one sample forwarded after the analysis) and the final result is a normal IR + direction info (azi and ele) for every single sample. In the reproduction, we take an IR from one omni mic (to get flat frequency response) and distribute the samples of it to corresponding reproduction loudspeakers. In other words, we convert one omni IR to convolution reverbs for all reproduction loudspeakers. An d then we convolve the anechoic music with these loudspeaker signals (=convolution reverbs). In our current listening room we have 24 loudspeakers in a 3D setup. The accurate direction for all samples can be obtained using VBAP, but it attenuates high frequencies a bit. Therefore, we just associate every IR sample to closest reproduction loudspeaker, which might introduce a small error in direction, but the frequency response (and sound color) is untouched. With the SDM method, the most authentic reproduction (of the sound in the concert hall) in the lab can be obtained. All the best, Tapio PS. If you want to have our JAES or JASA articles, just email be privately and I'll send them to you. -- Tapio Lokki <[email protected]<mailto:[email protected]>>, https://mediatech.aalto.fi/~ktlokki/ Aalto University School of Science, Department of Media Technology PO Box 15500, FI-00076 Aalto, Finland, tel. +358-40-578 2486, fax +358-9-4702 5014 [email protected]<mailto:[email protected]> kirjoitti 18.1.2014 kello 19.00: On 01/17/2014 07:29 PM, Aaron Heller wrote: Jan 2014 Physics Today just landed on my desk and the cover article is by Tapio Lokki on evaluation of concert halls. "Tasting music like wine: Sensory evaluation of concert halls" http://scitation.aip.org/content/aip/magazine/physicstoday/article/67/1/10.1063/PT.3.2242 It is labeled "free content," so should be available to anyone. interesting. what puts me off a little is that they used an ad-hoc mic array of six spaced omnis, without giving any details whatsoever. how good can direction estimates be with that kind of setup? and how do you ensure the reproduced diffuse sound field is accurate? the actual meat is in here, it seems: http://scitation.aip.org/content/asa/journal/jasa/133/2/10.1121/1.4770260 but sadly that one is not freely available. can't see myself paying $30 for a casual read... -- J?rn Nettingsmeier Lortzingstr. 11, 45128 Essen, Tel. +49 177 7937487 Meister f?r Veranstaltungstechnik (B?hne/Studio) Tonmeister VDT http://stackingdwarves.net<http://stackingdwarves.net/> -------------- next part -------------- An HTML attachment was scrubbed... URL: <https://mail.music.vt.edu/mailman/private/sursound/attachments/20140121/75602a53/attachment.html> _______________________________________________ Sursound mailing list [email protected] https://mail.music.vt.edu/mailman/listinfo/sursound
