Relevant Research

This site offers surround professionals an opportunity to exchange information, voice their opinions, and get their production questions answered by their peers. This was created for you to discuss issues pertaining to the surround sound revolution.

by tomlinson holman

The Proceedings of the AES 19th International Conference, Surround Sound: Techniques, Technology, and Perception were supplied to attendees (see the editorial) on paper and as a CD-ROM and will be available to those who could not attend from AES in due course (keep checking for updates). A sign of the maturation of surround sound as an industry is the quality and quantity of the papers at this conference, held at Schloss Elmau, Germany on June 21-24, 2001. Fifty-nine presentations (papers, seminars, posters, sound presentations, and a workshop) are documented in the work. As of the date of writing this, the titles of the presentations are on the Web site under the conference heading, so see the AES site for a complete list. It is again a good sign that there were simply too many presentations to cover them all here.

Paper sessions were devoted to room simulation and artificial reverberation, reproduction and evaluation, format conversion, microphone and mixing concepts, perception, and spatial rendering alternatives to 5.1-channel sound. Seminars were held on practical surround sound production for drama, TV documentaries, and music. Popular ones were given by David Griesinger (Lexicon) on distance, depth, and hall impression in 5.1-channel sound, and by George Massenburg on mixing technique for surround. Special demonstrations were held outside workshop time in a dedicated room with picture where applicable.
Here are some highlights of the papers.

“Optimization of Binaural Room Scanning (BRS): Considering inter-individual HRTF-characteristics,” by Gerhard Spikofski and Markus Fruhmann of the Institut f�r Rundfunktechnik describes the idea of coming into a control room with a dummy head and measuring the response at each ear for each loudspeaker channel, then loading up the results in a “BRS” processor so that you can use headphones and get the same response as your control room. A quick listen to the accom- panying demonstration in another room worked quite well, simulating the loudspeaker sound in the headphones – including timbre and direction. This looks like just the ticket to do that location remote you’ve always wanted to do in surround, but couldn’t bear setting up a monitor system on location. The authors say that the key to making it work well is to add head tracking to a fixed system, as shown in this paper. The head tracker is a metal triangle placed on the top of the headset. It makes you look like a Teletubby when wearing it, but the system does work.

Two papers were given on upmixing from two to multichannel, one by Philips’s Ronald Aarts and one by Dolby’s Ken Gundry on Pro Logic II. Logic-7 was also demonstrated in a Mercedes on the grounds. For recording engineers, among the most interesting were probably the microphone technique papers. Joerg Wuttke of Schoeps presented “General Considerations on Audio Multichannel Recording,” as well as a second paper, and chaired a “hot” seminar wrapping things up near the end of the conference. The referenced paper lists current main microphone techniques for 5.1-channel sound. The omnipresent David Griesinger wrote “The Psychoacoustics of Listening Area, Depth, and Envelopment in Surround Recordings, and their relationship to Microphone Technique.” He says in it something that I can completely confirm in my experience: “�but our experience points out the difficulties of experiments done on the spatial properties of sound. While audible and important, spatial properties are very easily masked by small differences in either the level or the spectrum of the systems under test.” How true it is. Many researchers simply don’t get this point and come to erroneous conclusions, sometimes after expending thousands of dollars and lots of man-hours.

G�nther Theile presented his paper that we covered here last issue, “Natural 5.1 Music Recording Based on Psychoacoustic Principles.” One thing I didn’t understand until I looked at the OCT physical setup is that the outlying left and right hypercardioid mics are Schoeps Vertical types, also called side address microphones (as opposed to end address, the “normal” type). This reputedly allows better response for the off-axis sound as used in OCT (optimized cardioid triangle) setups. Also, we cited a Web site last issue (, and, since we published that, the site has been translated into English. Go there and have fun. It is described in the paper “Studies on Main and Room Microphone Optimization” by Helmut Wittek, Oliver Neumann, Markus Sch�ffler, and C�line Millet.

Probably the least expected paper here was presented as a poster, aiming for a full paper at the New York convention. Aki V. M�kivirta and Christophe Anet presented “The Quality of Professional Surround Audio Reproduction, A Survey Study.” Loudspeaker responses for 372 monitors were taken in 164 professional monitoring rooms, and compared to the electroacoustic standards. The smoothed 1/3-octave band responses, with mean, minimum, maximum, and 50th and 90th percentiles are shown in fig. 1. (The level differences among the speakers were subtracted out.)

It can be seen that the 50th percentile curves (black) somewhat exceed the limits set by the standards, and the 90th percentile thoroughly breaks the standards. The message of this monumental work is to use better room acoustics to start, and use proper room equalization, something done far too infrequently. While the mean isn’t too bad, even it has audible deviations in the bass. (Remember these are smoothed curves.)

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