I have just about completed my room and started adding the seals around the door, when I got to thinking about testing the room for results.

I have the digital radio shack sound meter and was wondering if the following settings/procedure would be a good starting plase to measure results. In addition what results would be expected if construction was done well? I have a 25gal compressor in the room that I was going to use as a noise source since I do not have the audio hooked up yet.

Procedure:

1) Set meter to Response:Fast and Weighting:C
2) Turn on compressor
3) Take reading #1 in room with door closed at approx seat position meter pointed at compressor
4) Take reading #2 outside room door with door open meter pointed at compressor
5) Take reading #3 outside room door with door closed meter pointed at compressor (same as above but door is closed)
6) Take reading #4 from another room in basement (theater is in basement)
7) Take reading #5 from 1 floor above
8) Take reading $6 from 2 floors above


Has anyone else tested their results and if so what did you find?

Thanks in advance.

Curious to see what your results are.

Could you give a brief recap of what you did to soundproof the room.

GG + DD (1/2 + 5/8?)
Caulk the outlets?
Exterior door?

Thanks.

I think what you may find is that your meter does not go low enough. I can have things at about 90 decibels in the theater. I go outside the theater and I can still hear things but the meter doesn't pick it up (it is lower than the lower limit of the meter). Same with going upstairs. I can hear some bass but the meter does not pick it up. So, I think your results will be more qualitative (does the meter register anything or not) than quantitative (so and so is x decibels louder than...). Give it a try and let us know.

Ok I did a quick try when I turned on the compressor this morning.

I did some measurements around the house before I turned it on just to see what the ambiant noise level was for comparison. Bear in mind that I have two little ones running around up stairs and the A/C is blowing, but I got ambiant levels below 50-54dB. (50dB is the lower limit of the meter).

Here were my results

1) 92dB In room with door closed
2) 88dB Outside room door with door open
3) 66dB Outside room door with door closed
4) 56dB In basement adjoining theater room wall without door
5) Below 50-54dB. 1 floor up
6) Below 50 2 floors up

I also repeated the above with a radio in the room turned up (local rock station)
1) 84-88dB In room with door closed
2) 82-84dB Outside room door with door open
3) 64-66dB Outside room door with door closed
4) Below 50-54dB dB In basement adjoining theater room wall without door
5) Didn't measure
6) Didn't measure

Just for kicks I moved the radio into the basement bathroom to see what the results would be for a normal construction room. For this test since the room was much smaller I lowered the volume of the radio to match the in room level of the above test. Accross the board my results outside the room were about 6-7dB louder than the theater room tests.

I still have some seals to install around the door and stuff, but given the constraints I had to work with (lots of HVAC above theater room) and double doors (that was by choice) along with the fact that the dB scale is logarithmic I am fairly happy with where I ended up.

I would be interested in seeing what others get running similar test.

Curious to see what your results are.

Could you give a brief recap of what you did to soundproof the room.

GG + DD (1/2 + 5/8?)
Caulk the outlets?
Exterior door?

Thanks.

Staggard studs on common walls
Studs+GG+5/8+GG+5/8 (inside room walls and ceiling)
Studs+construction adheasive+5/8+construction adheasive+5/8 (outside walls)
R13 between studs (walls and where ceiling allowed)
caulked all drywall seams
Installed weatherstripping gasket under doors (around and between the doors has not been done yet)

Bear in mind I had an HVAC nightmare that I wasnt really willing to adjust above this room. Basically have the supply ducts for the upstairs and basement went between the joists above the theater and one of the main supply branches runs though the rear soffit of the room. In addition because of the limited in-ceiling space caused by the above the 4 can lights above the seating area are retro-fit fixtures and not sealed cans.

I think what you may find is that your meter does not go low enough.
Correct. The Radio Shack meter is great for calibration purposes, but it simply doesn't have the range to be useful for sound isolation measurement. Also, any sound level meter weighting, such as "A" or "C", will do averaging over its frequency range to give you a single number. STC (Sound Transmission Class) is a single number, but is calculated non-linearly, so as to read the loudest sound of its psychoacoustically weighted frequency range. It better matches what we hear, which is the loudest of the noise, rather than the average over all frequencies.

- Terry

Terry,

Is there any equipment, method, etc that you would recommend for us DIYers that we might be able to use in order to compare the real world results of our efforts. I have frequented the forums for years at this point and there are TONS of great tips, techniques and lab data, but when it comes to the results of the builds its always very subjective (aka "It sounds good to me").

I myself am more than happy with my results and wouldnt change anything even if I had numbers, but the engineer in me still would like take some measurements, see the numbers and be able to compare them to the results others have obtained. I think this would be a great benifit to those just getting started as well.

Any advice would be appreciated.

Correct. The Radio Shack meter is great for calibration purposes, but it simply doesn't have the range to be useful for sound isolation measurement. Also, any sound level meter weighting, such as "A" or "C", will do averaging over its frequency range to give you a single number. STC (Sound Transmission Class) is a single number, but is calculated non-linearly, so as to read the loudest sound of its psychoacoustically weighted frequency range. It better matches what we hear, which is the loudest of the noise, rather than the average over all frequencies.

- Terry


Thanks for the clarifications, Terry. I tried to do this as well and failed. Set speakers to 100 dB test tones and even before drywall went up it was difficult to measure anythign on the RS meter. No hope of quantifying the effects of DD+GG, door, etc.

Terry,

Is there any equipment, method, etc that you would recommend for us DIYers that we might be able to use in order to compare the real world results of our efforts.
Hi Mike,

Sound level meters at the $100 price point can go down to 30 dB. But for noise isolation measurements, I wish there was something inexpensive that I could recommend. The higher-end multifunction meters for pro acousticians and HT calibrators can do this. The only reason it is expensive is that the market will bear high prices for this stuff.

PC software set up for audio input could do this relatively easily -- measuring NC (Noise Criteria) levels, for example. But I don't know of any inexpensive software for this. :(

- Terry

Thanks Terry,

Oh well. Would have been nice to try. Maybe this thread will spur some software development from the members here. I would play with it myself, but I have a theater to finish.

Thanks again for the info.

You might try using a measurement microphone like the Behringer ECM8000 (with pre-amp) or a similar microphone. First using pink noise (at a reasonable level) and an SPL meter get a reference level for the ECM8000 then do the noise test. It won't be real accurate but it will be somewhat repeatable.