AES Section Meeting Reports

Pacific Northwest - March 25, 2009

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The PNW Section's March meeting was held March 25, 2009 at Opus 4 Studio, Bothell WA, with James D. (JJ) Johnston talking about spatial perception in audio and home theater versus cinema. After remarks from PNW Chair Steve Turnidge and venue host Dr. Michael Matesky/Opus 4 Studios, attendees did self-introductions. 20 AES members and 21 non-members attended.

JJ discussed how producing good multichannel audio for a home theater should be different than for a cinema. He showed that long known acoustic and psychoacoustic principles and modern production tools make it possible to utilize a home theater audio system more effectively compared to cinema, but that this makes home theatre production more complex.

The rooms are quite different in size, dimensions, and acoustics, meaning a listener's differential time delays from the speakers are different, and so is the availability of phantom images. In the cinema - the focus must be on the dialog and "holding the front".

In the home, the sound design tries to convey all of what the cinema does, but also can provide a stable image and a sense of envelopment, while avoiding focus on rear and back channels over a wide listening area, by using the interactions between all channels.

JJ went into more details on human hearing, directional cues, diffusion and envelopment and how it can work to advantage in the home theater. He noted that as the home setup has a short reverb time, synthetic diffusion allows creating a big room in a home theatre. The converse, a small room in a cinema, is problematic. The need for a center channel has also been proven since the 1930s. The key to good envelopment in home theater is to get good diffusion/interference in the space to get different envelopes at the two ears. Time+amplitude panning is much more effective than amplitude panning. Lastly, he advised producers to always remember the human auditory system and to make sure any reverb is properly decorrelated channel to channel.

Then a break was held with refreshment from Opus 4 Studios, and door prizes awarded.

Afterwards, sound demos were done by JJ assisted by Steve Hastings. The effects were generated "live" on the laptop computer, and played on the house stereo. The examples were a professionally recorded, famous-name voice artist, with various changes done to illustrate recommended enhancement methods. Examples included dry sound, delay panning with a little reverb, and distance panning.

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AES - Audio Engineering Society