After having seen a very loud concert, I got to thinking about sound. Since I have little (read: no) actual knowledge about it, I thought I’d ask my admittedly unimportant question.
Let’s assume that band A is playing at a small club at a very high, but constant, volume. Would the number of people in the club affect how loud the sound is? I mean, if the volume was the same regardless of the number of people, would there be a detectable difference depending on if the place was packed or if it was completely empty? I’m assuming that sound waves would get absorbed more with all the people in the room. But would the difference be detectable?
Yes, it does matter. In fact, not just the overall volume, but the volume of different frequency bands change depending upon how many people are there, and where they are. That’s why the sound board operator is adjusting things through the entire concert. How detectable it is depends upon the ear of the listener.
The initial volume of the music (or whatever) would be the same (i.e., if you were standing next to the speaker in an empty room vs. a packed one, it’d sound the same to you). The only difference in volume you would detect, I think, would be a slight reduction in resonance. In an empty room the sound waves reverberate off the walls, causing, well, if not an amplification of sound, then at least a longer-lasting song. I’m led to believe that everybody in the room, with their sound-absorbing clothing (now isn’t that something Madison Avenue should say?) has the same effect as playing in a “dead” (that is, carpeted) room. To elaborate, pretend I’m playing the trombone in an empty room lined with tile (or some other non-porous surface). Then I move to a similar room lined with carpet (or other porous material), thus duplicating the effect of lots of people standing around. If I play at the same volume, it sounds the same, but the sound doesn’t “linger” as long. That’s it (I think). I’ll let someone else handle the technical aspects of it.
As mentioned, and empty room would reverberate more than a packed room. Bodies absorb and filter sound in certain frequencies. If I was standing at the back of a packed room, I won’t hear the highs as much, as well as the sound would be attenuated simply because there are 100 people between you and the speaker. The sound isn’t produced louder in either case; the guitar amp is still on 11 no matter which room you’re in, but since there are people between you and the source, it will generally be quieter.