Church Acoustics, their applications to unbuilt small rooms

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Church Acoustics, their applications to unbuilt small rooms

Postby Bob » Sun Feb 29, 2004 5:31 am

This is just some personal observations, recorded, hopefully, for your curiosity.

I've been reading about acoustics for 2 years now. Until today it's been all math and spreadsheets.

Today I went to a new church. When I say new, I mean it was built over the past couple of months. We were curious about it, and it's closer than our regular, much older, and smaller one.

Right away I started noticing things that I could give names to. I could hear direct sound, first reflected sound, sound field, RT60. I've never noiced those four separately anywhere before, but I never knew to listen for them either. There was no echo or flutter. I don't think I could hear comb-filter, but I can tell you that voices, both spoken and sung from the choir, were not clear. The unclear voices could have been the acoustics of the room, or it could have been a simple mixing problem (i.e. a couple of volume/treble knobs).

The church is about 150'x150'x20' rectangular, with a pyramid ceiling rising another 50' to the middle. An interesting thing was the bare concrete floor of the entire church was slanted/sloped so that the alter is set about 6' lower than the floor at the gypsum walls. While the wood pyramid ceiling was four sided, the floor is a dish (evenly curved in all directions). The guy in the wheelchair had to set the parking brake to keep from rolling downhill. The place can easily hold two thousand people, but there were less than two hundred people there.

The sound from the choir was equally loud direct from the choir, and a reflection from high up the opposite side of the church. That reflection's only possible straight line path would be off the pyramid ceiling and then off a wall on that side before returning to me. The RT60 seemed to be about 1.1 to 1.2 seconds before the sound field disappeared. The choir had six microphones in front of their mouths, none on the instruments, and another 9 hung from wires from the ceiling 11' above the floor, and they had 2 large monitors pointed at them, but I didn't hear the choir out of the church main speakers. I'm not saying that it wasn't coming out of the church main speakers, but if it was then the volume was turned down. The guitars sounded ok, and the organ sounded good.

I think I've started to understand why people have been saying that, from dead to live:
a) spoken voice can be done in a dead room
b) A good singer's voice can be recorded in an a mostly dead space.
c) home theater should be in an absorbant room (but not dead), and carpet might actually be a good thing since it absorbs voices and gunshots, but lets the bass of the music linger
d) control/mixing rooms can somewhat absorbant
e) music should be played in a somewhat live room
f) musical instruments should be played/recorded in a live room (without flutter)
because, respectively, based on the components of what I heard today,
a) will help clarity (assuming you're facing the direct path) - the volume of the RT60 interfered with the understanding of the inflections in his voice.
b) is a tradeoff between support and clarity
c) effects are quick, therefore a sound field is bad. The only liveness you need is for ambience so the background music doesn't sound awful.
d) This gives you a little more hearing what's on the 'tape', but still enough ambience to enjoy it
e) music's nicer half may be in the sound field
f) the room can help the instrument. Actually a 50' diameter, round, 75' tall room, would probably be a very nice place to record instruments.

Of course I may be deluding myself.
Regards
Bob Golds
"The only thing we regret in life is the love we failed to give."
"Be a rapturist -- the backward of a terrorist. Commit random acts of senseless kindness, whenever possible" - Jake Stonebender
Bob
 
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