Soundproofing

[jack6428]

Hello again,

Sorry for so many posts at once, hope this is OK.

Also, I know this post isn?t exactly Altec only, but I?m thinking maybe some others may have this problem.

I have been busted by my neighbor for the music being too loud and am now so paranoid I can?t enjoy the music. This didn?t use to be a problem when I lived in the Midwest since I was sentenced to the basement (my gain). It also wasn't such a problem until I got my A7/828's this summer.

My first step is too make plugs (basic home insulation panels stacked with some space in between) to fit into and over the two window cavities in the room. I then started looking on the internet for more specific materials and methods. The info I?m finding is pretty general, leaning towards a sales pitch only. The house is what it is so making staggered studs out. Also, I don?t have the room to spare to make a double wall (room in a room). Dealing with special clips probably isn?t going to cut it either since they say if they?re not perfect it won?t work well.

From what can tell, there seems to be three choices (or combinations of them):

- acoustic foam panels (several kinds available)
- hi-density mass loaded vinyl barrier (kind of like a heavy rubber sheet, they say this actually absorbs the energy (turns into heat?))
- special drywall
- egg crate foam

My best guess is this (stack up over the existing drywall):

1. Glue (not nail) on another sheet of drywall (or the special sound reducing kind), they say use a thicker size than the original. They say not only does this reduce sound transmission but it also lowers the resonant freq of the room ? I think this means the house won?t shake and rattle as much until you reach really low freq, so it will be less apparent outside.
2. Add (glue or staple?) on mass loaded vinyl barrier.
3. Add (glue or staple or nail) on acoustical panels.
4. Add eggcrate foam (I think this just mostly helps keep the sound reflections in the room down).

I'm also wondering if I did do a double wall but use 2X6's placed 90 degrees rotated, whether I could not do one of the item aboves, or do it with all the items above and really complicate it.

Has anyone done anything like this?
Is this overkill (assuming it makes any technical sense to begin with?), what would the compromise be?
Any pointers on the gluing vs nailing etc?
Anyone know of material sources in the southwest (within a couple hundred miles of LA)?

Thank-you,
Jack

[Adhoc]

Hello Jack,
Of course it is the bass sound your neighbours complain about. 1 st step for me would be to isolate the cabinettes from the floor. Easiest done with some rubber pucks of suitable diameter. A good rubber would be natural rubber (the brown type used for rubber bands, also called Para Rubber). Hardness of this one is about 40 Shore A.It is really soft and will pretty well prevent bass vibrations going into the buildings structure. Another option would be high density foamed rubber of any quality (EPDM, neoprene, natural rubber etc.)The common black rubber used for gaskets, etc usually has a hardness of about 70-90 Shore A and does not work as well. The higher the number the harder the rubber and also the worse vibration isolator.

To do anything about air transitted bass waves which makes your walls shake is a different matter. Check out the web pages below and you will find some options. If you follow what's in them not only will your neighbours be happier. <u>You </u>will also we a lot happier with the sound in your room. The acoustics in your room will be improved a lot without any expensive fancy electronic gadgets. I build 2 panel absorbers for deep base (behind speakers) 2 large roof mounted mid bass absorbers (100-300 HZ) and some thin absorbers for the side walls to kill early reflection sound waves in the mid to high frequency. The improvement in sound was HUGE!

The guy behind the web pages, Ethan Winer, is a former rock musician who changed over to studio engineer and cello playing (!).
http://www.ethanwiner.com/acoustics.html
http://www.ethanwiner.com/basstrap.html
http://www.ethanwiner.com/BTPlans.gif

Regards
Kurt

ps As English is not my native language, I hope you excuse any bad spelling or ambiguities. 'From Stockholm, Sweden, by the way

[Adhoc]

A small addition/clarification: From my listening position, the absorbers I made for my room decrease the amplitude of standing waves/resonances/room modes in the bass range, and results in a much clearer sound in midrange and upwards, as early reflections from side walls and ceiling are deadened. -If the direct sound from speakers and reflected sound from the walls reaches your ears within about 20-30 ms, your brain is not able to separate the sounds. The result is a "smeared" kind of sound, instead of "pure" direct sound. So you will loose out on the fine nuances in the music with these early reflections. A heavy curtain would also do the trick, a book shelve at the right place with books / objects haphasardly placed in it can work well as a diffuser and also improve sound in the room.

A down side with absorbers is that you have to turn up the volume knob a knotch, compared to before. In my case about 4-6 dB from my listening position. A low price to pay, as the sound gets so much improved, no listening fatigue anymore from poor sound. also I seldom listen at rock concert levels at home.