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  1. #1

    noise reduction - help

    Our church is surrounded by 3 busy roads less than 20ft from the sides and sometimes feel the existing sound system is inadequate. The trouble is,
    • Audio system is set to the optimum level, to avoid feedback.
    • We have few stained glass windows and doors opening towards the roads.
    • Space is very limited inside.


    Seems noise reduction is the right thing to do.

    Can anyone suggest cheap, environment friendly & fire retardant materials that can be used outside the building ?.

  2. #2
    ermm one thing i can suggest is egg cartons but then burn like hell. another one is polystyrene, i don't know if that burns or melts or what. I'm sure there are better ones but those are my home made remedies

  3. #3
    Do you open the doors and windows? If so, you're out of luck - nothing will help. (Sound absorbent in the room will suck up as much of the sound you want as sound you don't.)

    You need to discriminate in favor of one kind of sound and against another. Once sound gets into a room, the very best sound absorbents won't help much. You have to keep sound from getting into the room.

    If I may assume you don't open those windows, the best solution is very thick, heavy glass. The next best solution is several layers of regular glass. You've already got one layer in the stained glass; now it's time to add another, even if you don't need it for thermal reasons.

    You probably can't block off the doors because they're needed as fire exits. What you can do is 1) keep them closed; 2) put tight weatherstripping around them; 3) if they're light hollow-core doors, replace them with solid-core or attach a 3/4-inch thick piece of MDF to one or both sides (if they're glass-sorry); 4) add a second door outside each of the first ones. Line this second door with a tough acoustic absorbent material. (Acoustic tile will get wrecked in two weeks.)

    You didn't mention the sonic character of the road noise - is it a "roar" or a "rumble?" If it's a rumble, that means it's mostly low frequencies and the windows and doors are already doing about as good a job as they can.

    An acoustic consultant can design resonant traps specifically tuned to low frequencies. You can safely suck up as much low frequency energy as your budget will permit, since most voice and instrument sounds occur at midbass-to-high frequencies.

    Acoustic absorbent placed against a reflective surface will not absorb low frequencies. It has to be mounted out from the surface at least 6 inches to work even at mid-frequencies. This mounting method is much more important than the actual material you choose. The "deadest of the dead" is 6-inch fiberglas covered with a cushy fabric like overcoat liner, with both covered by a thin decorative fabric. If you do decide to put up absorbent, try to locate any existing sources of echoes (parallel walls, hard back wall etc) and cover those surfaces. When the general reverberant character of a room is damped out, any hard echoes that may exist become more exposed and you can actually wind up losing speech intelligibility.

  4. #4
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    If acoustic treatment is not an option or still doesn't do the job, you could consider distributed audio or a combination of traditional front of house speakers and distributed audio. I did an install at a church with similar issues and used front of house speakers for the praise band and distributed audio speakers for all "talking head" (pastor, cantor, etc.). By putting a speaker in the vicinity of every listener, you can boost the power to overcome the ambient noise without as much concern with feedback. It worked well for them.

  5. #5
    I'm a big fan of dual systems like that, and not only to overcome acoustic problems. Music and speech are so different, and their requirements differ so much, that you get better results with two systems than one, no matter how good that one may be.

    A side benefit is that the musicians then have complete freedom to screw around with their system without getting the clergy involved. And the clergy doesn't have to wonder how the speech system will have changed since last time it was used.

  6. #6
    Thank a million guys,

    Quote
    Quote: karl eilers
    View Post
    Do you open the doors and windows?
    Not the windows, but the doors. The doors are heavy wooden ones plus extra glass doors.

    You didn't mention the sonic character of the road noise - is it a "roar" or a "rumble?" If it's a rumble, that means it's mostly low frequencies and the windows and doors are already doing about as good a job as they can.
    Well, it is a mix bag, mostly "roar", depending on the vehicles outside, i think, it is the roof that causes much of the noise.

    Regarding the installation of absorbent, i was thinking of installing it outside the church, much like a bubble, anyway it isn't a magnificent building.

    Quote
    Quote: khnervick
    View Post
    If acoustic treatment is not an option or still doesn't do the job, you could consider distributed audio or a combination of traditional front of house speakers and distributed audio. By putting a speaker in the vicinity of every listener, you can boost the power to overcome the ambient noise without as much concern with feedback.
    To be honest, i don't like the idea of a sound system for a traditional choir like ours. Especially with the attitude of some sopranos and altos, and they tend to ruin the whole thing by singing loudly and directly to the mic.

    One thing i forgot to mention earlier is, when there is no traffic, a couple of us singing quartet from the altar can be heard clearly at the main entrance with the church empty. What are my options to increase acoustics inside, apart from preventing outside noise entering the church ?.

  7. #7
    When you install acoustic absorption in the building, you decrease the carrying power of, say, a quartet at the altar or a choir. Many a church has installed padding only to find that they now need to amplify the choir to make up what was lost.

    I dislike amplifying a choir too, because there is no sound system made, for any amount of money, that does not damage the sound quality. There's a good reason why a symphony orchestra pays a fortune to have a hundred unamplified musicians rather than fifty amplified ones.

    Padding on the outside of the building isn't going to do anything. You can't suck up all the sound in the neighborhood any more than you can put an air conditioner outside and suck up all the heat. As far as blocking noise coming through the walls goes - acoustic absorbers are good at absorbing sound within a room, but not good at keeping it from going from one place to another. This is one of the Great Misconceptions about acoustics. Absorbents do not block sound. And if the doors are open, all the sound leaking in through other paths is irrelevant.

    I assume you don't always have the doors open. When all the doors and windows are closed, what happens? Is the road noise still a problem?

  8. #8
    Think outside the box... figure out a way to divert traffic (otherwise, karl is, as always, on the right track)
    Eric Adler (tonsofpcs)
    http://www.videoproductionsupport.com/ Chat at: http://tinyurl.com/vpschat
    Follow me on twitter: @videosupport @eric_adler

  9. #9
    Quote
    Quote: karl eilers
    View Post
    I assume you don't always have the doors open. When all the doors and windows are closed, what happens? Is the road noise still a problem?
    We keep the wooden doors open. Road noise is a problem even with wooden and glass doors/windows closed.

  10. #10
    Okay. Noise is probably not coming through the wood and glass, and whatever noise is coming in that way will be low frequency, below 300Hz, which isn't going to interfere with voices much. It's leaking in around the edges. When they build multi-screen movie theaters, they have to make sure there is no sound path thru the air. Not even a pinhole.

    Two questions - first, is the church extremely reverberant, like a small cathedral? Second, what is the character of your music - traditional, liturgical, modern, blended, varied? It is possible that if the church is very reverberant and your music tends toward modern, you could put up a limited amount of padding without hurting the music too much. Then again, a person sitting in a pew is equivalent to a yard square piece of acoustic tile. So you've already got padding, except when the church is empty.

    If it were me, the next thing I would do is rig a stethoscope by taking the smallest mike I could find, a battery-operated amplifier(a portable recorder in record mode will usually work) and headphones. Put the mic on a stick and sniff closely around the edges of the doors and windows. You are likely to find specific places where the majority of the sound is sneaking in. Put weatherstripping in those cracks.

    Just for reference, if you want to completely kill noise infiltration, so you have essentially a studio environment, you're going to have to seal off the windows and put heavy, gasketed fire doors in. That's not the answer you wanted, but as Scotty always told Captain Kirk, you can't change the laws of physics.

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