Cheap Thoughts: Acoustics

I have good hearing. I guess I come by it naturally, since my mom (at least) has good hearing, too. One of the reasons I never snuck out of the house as a kid like my brothers (and sister, so far as I know) did was knowledge of my mom’s hawk-like hearing. Then again, my hearing could also be a product of my former employment, once as a recording engineer and again as a code-copier in the Navy.

Yesterday, I commented to my office mate how the air conditioning sounded like one of those annoying cars with a thumping bass amplifier. I could hear the blower units above my head resonating, producing a deep bass beat frequency. “Wow, you must have sensitive ears,” he commented. Apparently he didn’t hear it as well as I (and I wished I didn’t!)

On my drive up to Pennsylvania, I stopped at an outdoor mall to grab dinner. As I got out of the car, I caught the sound of music all around me, echoing around the buildings. I was fooled into thinking a live band was playing nearby. Instead, I discovered outdoor speakers were the source. It’s very rare that my ears are fooled by a recording, but something about the acoustics had that magic that is normally missing in played-back music. I think it was the timing, or the shape of the buildings. Maybe the bass I heard that seemed to come from one direction.

As I pondered this rare error of my ears, it occured to me that part of the problem of recorded music lies in the shape of the speakers which play it back. The sound from a live music source – say, a trumpet or a drum kit – is not unidirectional the way a speaker is designed to be. The sound comes from all directions. Speakers which project sound largely in one direction can’t help but distort the sound.

What if speakers could be designed in a sphere shape, projecting sound in all directions? How would the sound from one differ from a unidirectional speaker? How could such a speaker be easily manufactured? Or designed, for that matter?

What about a microphone to match? Sure, most microphone heads are round, but only some are omnidirectional. Even then I assume the element inside favors one direction over others.

Its times like these I wish I knew more about acoustics (and electrical design).