[CQ-Contest] Soundproofing?

[Jim Brown]

GM Steve,

In that case, the advice from K0SN is in the right direction. But that 
part of soundproofing can be quite difficult, especially for low 
frequency sounds. Sound can leak through holes or gaps in the sort of 
sound proofing that he describes.

Sound is air vibrating, and it goes through walls by making them 
vibrate. That's where mass comes in, making it more difficult for them 
to vibrate. Low frequency sounds are the most difficult to block. Higher 
frequencies are easier. We can beef up walls, but sound leaks through 
doors, even when closed.

I designed sound systems for major projects -- theaters, churches, 
stadiums, jazz clubs -- and was working closely with heavy duty acoustic 
consultants whose job it was to both make the room ultra quiet and to 
make it sound good for listening to music. Over the years, I learned a 
lot by paying attention.

Inside rooms, sound bounces off all the surfaces, conserving its energy 
and making it louder. Sound sources (speakers, for example) couple to 
surfaces they're mounted on, making them vibrate, and the sound they 
make bounces off of surfaces. We can reduce the overall level of sound 
in rooms by making as much of that surface area "soft," and 
concentrating on surfaces near the sound source and that the source is 
pointed at. Surfaces that speakers are sitting on will be vibrated by 
the sources, and we can reduce that by placing thick soft "stuff" 
between the speaker and the surface. All of this reduces the overall 
sound level in the room, so there's less to leak out through walls, 
windows, and doors. In one project I worked on, the Staple Center, lots 
of large, thick fiberglass bats mounted to both sides of plywood are 
suspended from the ceiling for this purpose.

Doors need to be heavy, and the seals need to be very good. Studios and 
entertainment spaces have heavy double doors, with space between them. 
Vibration through walls is minimized by building "rooms within rooms," 
where the studio sits on carefully calibrated springs, and the room has 
no connection with walls of adjacent spaces.

Sound also leaks through HVAC ducts.

So -- I would start with "fuzz" -- thick layers of sound absorption on 
walls you're facing, use headphones rather than speakers, beef up the 
walls as K0SN has suggested, look at doors and windows. The cheapest 
effective "fuzz" for walls is thick fiberglass facing the wall. I used 
that in the house I owned in Chicago -- there was a fabric store that 
would build a frame to which they would mount their decorative fabric. I 
put thick fiberglass on it and hung it from a wall. On another wall, I 
hung a decorative shaggy rug with fiberglass behind it. In my shack here 
in W6, I've sat my power amps on soft "stuff" and put "fuzz" on the 
walls behind them to minimize fan noise.

73, Jim K9YC

On 11/4/2021 10:46 AM, k7lxc at aol.com wrote:
>  >  Define "soundproof." Do you mean to prevent outside sound from coming
> in, or do you want to prevent it from reflecting sound that hits it from
> inside the room?
> Hiya, Jim -
>      I don't care what happens in the shack. I want to keep my noise out 
> of the adjacent room and keep their noise out of the shack. I want to be 
> able to operate a phone contest and not disturb the neighbors.  I want 
> to be able to operate in relative privacy - it's a shared wall.
>      And it should be cheap. I don't need a sophisticated expensive 
> solution. So far another layer or 2 of wallboard may be the way to go 
> according to my feedback so far. Thoughts?
> Cheers and tnx!
> Steve     K7LXC
> PS - I bought a bunch of "acoustic" tiles which appear to be a bunch of 
> holes bonded together. I put 3 layers on each ear and figured there was 
> about 1 dB attenuation. Pretty useless.