Thursday, June 24, 2010

Walls and Sound

Back a while ago I posted on how much better the community band sounded when set up right in front of a wall in the town park as opposed to being out in the middle of it. We could hear ourselves better and the audience could as well.

Last week the Kenwood Players performed what Erik Satie might have called "furniture music" for a Health Fair put on by U.Va. hospital and a number of local non-profits.
Free mammograms and sports physicals for school children, along with lots of information booths and free screenings, were on offer for non and under-insured folks.

The locale was the gym in the new field house at the high school in town. The way we set up, Dick on trumpet had his back directly to a wall and Bill B on soprano sax had his back to the corner of the huge room furthest from us. In the recording, Dick is perfectly clear and Bill B sounds as if he's in the next county, and they were equidistant from the mics. 

At the time we were playing this disparity wasn't obvious because of the booming acoustics of the gym and because I was usually standing closer to Bill B than to Dick. There was also a thick pad on the wall right behind Dick and I assumed it would soak up a lot of his sound, but anything reflects better than nothing. Also, the recorder was out in front of us a bit, and other than setting a level, I didn't really pay attention to the sound and the balance.

The basic lesson in all of this is not to make assumptions, but to walk around and pay attention to how the acoustics are working.


  1. I've been in one of these anechoic chambers they use for the acoustic testing of telephones, where the walls in all directions have foam padding designed to completely absorb all sound.

    In one of these places, if somebody turns away from you and speaks, even though they are only 3 feet away from you (these chambers aren't very large), their voice is barely audible. The voice produces sound which is very directional, and if you don't happen to be on the direct path, you rely almost entirely on reflections off the surroundings to hear what other people are saying.

    The same applies of course to musical instruments. The horn is obvious, but it is surprising how directional sound can be from woodwind instruments as well. And even stringed instruments are directional to some extent - that is why the first violins are placed to the conductor's left in an orchestra, so that with the angle of their instruments, their sound is projected forward towards the audience.

    For this reason, the acoustic architecture of concert halls is a highly mathematical and scientific endeavour these days, so that the sound is available equally (as far as possible) to everybody in the audience.

  2. Jonathan - Great info. Thanks. Hadn't realized the directionality of strings.