Sunday, October 12 2:00 pm – 4:30 pm
Session L Room Acoustics

L-1 Low Frequency Absorbers—Applications and Comparisons— Dirk Noy, Gabriel Hauser, Walters-Storyk Design Group Europe, Liestal, Switzerland John Storyk, Walters-Storyk Design Group, Highland, NY, USA
One of the major issues in small to medium room acoustics is low frequency response and behavior. The goal of this paper is to present how and in what magnitude different commercially available low frequency absorbing devices control low frequencies in real world applications. Reproducible acoustical measurements have been taken in a completely untreated rectangular concrete room, sequentially with and without a total of eight different absorbing devices as courteously provided by eight different international manufacturers. Results are compared and conclusions are presented.

L-2 Sensitivity of Multichannel Room Equalization to Listener Position—Sunil Bharitkar, Philip Hilmes, Chris Kyriakakis, University of Southern California, Los Angeles, CA, USA
Traditionally, room response equalization is performed to improve sound quality at a given listener in applications ranging from automobile, home-theater, movie theater, and/or multimedia education in classrooms. However, room responses vary with source and listener positions. Hence, in a multiple listener environment, equalization may be performed through spatial averaging of magnitude responses at locations of interest (e.g., in movie theater equalization). However, the performance of averaging based equalization, at the listeners, may be affected when listener positions change, or due to mismatch between microphone and listener positions (i.e., displacement effects). In this paper we present a statistical approach to map displacement effects to a magnitude response averaging equalization performance metric. The results indicate that, for the analyzed listener configurations, the zone of equalization depends on, (i) distance of microphones/listeners from a source, (ii) the listener arrangement, and (iii) the source signal spectral composition. We have also provided an experimental validation of the theoretical results, thereby indicating the usefulness of the proposed closed form expression for measuring equalization performance due to displacement effects.

L-3 In-Room Low Frequency Optimization— Todd Welti, Allan Devantier, Harman International Industries, Northridge, CA, USA
At low frequencies the listening environment can have a significant impact on the sound quality of the audio system. Standing waves within the room cause large frequency response variations at the listening location. Furthermore, the frequency response changes significantly from one listening location to another; therefore, the system cannot be effectively equalized. A novel method to reduce seat-to-seat frequency response variation is described so that the system may be equalized over a relatively large listening area using relatively simple processing.

L-4 Hybrid Equalization of a Room for a Home Theater System—Lae-Hoon Kim, Jae-Jin Jeon, Sin-lyul Lee, Koeng-Mo Sung, Seoul National University, Seoul, Korea
For home theater systems, it is necessary to equalize the room impulse responses. It is well known that the perfect inverse filtering over the entire audio frequency range is hard to be met due to the perturbations such as a listener’s head movement. For securing a larger “sweet region” we measured at 18 points 3cm at regular intervals horizontally around both ears. We synthesized one representative impulse response of these 18 impulse responses in the position-weighted manner using principal component analysis method. We then applied this representative impulse response as the target of inverse filtering. For inverse filtering we applied two different methods into two frequency ranges. In the low frequency range we realized a perfect inverse filter using least square method; in the high frequency range we realized linear phase finite impulse response inverse filter using one-third octave band frequency magnitude response smoothing. Using this inverse filter we can confirm well-equalized high sound quality in the entire sweet region from the result of experiment.

L-5 Audio Production in Large Office Environments—Eddy B. Brixen, EBB-consult, Smorum, Denmark
In an increasing number of radio facilities, large office environments are used for audio production. Program material is prepared, edited, and finished ready for broadcast on DAWs without using studio acoustics, studio microphones, level or loudness metering, loudspeaker monitoring, or even audio engineers. In many aspects this affects the sound quality. In this paper the drawbacks are discussed, and suggestions for technical solutions are presented.