Noise Control / Room Isolation

[gedlee]

(this thread split off from here Geddes on Distortion perception )

Originally posted by soongsc

Soundproofing a wooden house is much easier.

Having done noise control for a good part of my life, I can tell you that I would much rather start with a nice solid concrete structure. If you are getting sound leakage in a concrete building then you can be pretty sure that its not conductive through the concrete. There is some other path. Most people don't consider all of the possible paths of sound - this is the biggest downfall. even one small leakage hole can short circuit the whole job. But I think that its reasonable to conclude that concrete is not going to be one of the major paths.

Wood structures on the other hand are very good at transmitting sound structurally, so sound issolating my wood frame house was a real challenge. In the US the major path is the HVAC and thats a tough problem to solve.

[KSTR]

Originally posted by gedlee
Having done noise control for a good part of my life, I can tell you that I would much rather start with a nice solid concrete structure. If you are getting sound leakage in a concrete building then you can be pretty sure that its not conductive through the concrete. There is some other path.

My personal experience differs, and I have it 2-3 times a week. I live in in the 2nd floor of a city building all with brick walls and in the basement / 1st floor there is a live music club. All of the noise getting trough to my appartment comes through the solid walls, expecially the one that I share with the club. Snare drum hits I've measured with 90dB(A) and more close to the wall. The leakage through other paths, especially the stairway, is negligible.

I also did soundproofing for various musician's practice rooms and in general the rule was: never ever let the sound hit the concrete/brick walls, once it's in there you can't get it out anymore. Which usually led to a floating "double box" structure.

- Klaus

[soongsc]

Originally posted by gedlee


Having done noise control for a good part of my life, I can tell you that I would much rather start with a nice solid concrete structure. If you are getting sound leakage in a concrete building then you can be pretty sure that its not conductive through the concrete. There is some other path. Most people don't consider all of the possible paths of sound - this is the biggest downfall. even one small leakage hole can short circuit the whole job. But I think that its reasonable to conclude that concrete is not going to be one of the major paths.

Wood structures on the other hand are very good at transmitting sound structurally, so sound issolating my wood frame house was a real challenge. In the US the major path is the HVAC and thats a tough problem to solve.

I have lived in concrete apartments in New York, wood apartments in TX, houses in CA, concrete apartments and town houses in Taiwan, I can say that the TX and CA experience were the quietest. For concrete to not conduct sound, the building must be structured like a 20 story building. I agree there are apartments in those kinds of buildings. But anything below that, the structure is not that thick. I've seen people that had to build a roon sort of floating in a room for their listeing room.

[gedlee]

Originally posted by KSTR
My personal experience differs, and I have it 2-3 times a week. I live in in the 2nd floor of a city building all with brick walls and in the basement / 1st floor there is a live music club. All of the noise getting trough to my appartment comes through the solid walls, expecially the one that I share with the club. Snare drum hits I've measured with 90dB(A) and more close to the wall. The leakage through other paths, especially the stairway, is negligible.

I also did soundproofing for various musician's practice rooms and in general the rule was: never ever let the sound hit the concrete/brick walls, once it's in there you can't get it out anymore. Which usually led to a floating "double box" structure.

- Klaus

I think that you are taking my comments out of context. IF the wall that you share with that club were wood it would be much worse - don't you agree. The floating double box on concrete is always my solution of choice - thats what I have in my home. I once did this floating room inside of a wood structure and it was no where near as good as the one grounded to concrete. Even concrete will conduct some sound, but a wood structure will be worse. Except perhaps in some of the very old warehouse structures made with huge Oak beams to carry the load of the storage above. These can have pretty good noise isolation from the massive overkill of the existing structure for residential use.

That must be a very loud club or a very poor brick wall, because a brick wall should have an STC (Sound Transmission Coefficient) of about -40 dB. But you said that the club was below you, so wouldn't that be the floor, is that concrete? Something of what you said doesn't add up.

[KSTR]

Actually I can compare both wall types, as the floor of my kitchen is the ceiling of the club and it is a pure wood construction (double panels, filled with wool, and yes, oak beams -- the building is from 1880 or so). Its response is very different from the solid wall -- lot's of deep bass shaking the dishes in the cupboard but very little content of higher frequency. Indeed the rumbling is louder in the kitchen in absolute SPL terms but the spectrum is, to me, way more pleasing than what I have in my living room (which has very dry, recording studio style acoustics, while the kitchen is really "live"). The living room is not directly above the club, it only shares the main wall.

And yes, it is a small but loud club (live rock music and stuff) and there is not much soond proofing wrt the walls. The wall in question is one of the main walls which holds the whole buliding, more than two feet thick. When I hold my ear against it I can actually hear people's conversations. I'm personally involved with the club (I do all the technical stuff, and the live mixing at times) so the noise is not an issue for arguments.

Of course I didn't intend to generalize this single isolated experience....

- Klaus

[gedlee]

Originally posted by KSTR
Actually I can compare both wall types, as the floor of my kitchen is the ceiling of the club and it is a pure wood construction (double panels, filled with wool, and yes, oak beams -- the building is from 1880 or so). Its response is very different from the solid wall -- lot's of deep bass shaking the dishes in the cupboard but very little content of higher frequency. Indeed the rumbling is louder in the kitchen in absolute SPL terms but the spectrum is, to me, way more pleasing than what I have in my living room (which has very dry, recording studio style acoustics, while the kitchen is really "live"). The living room is not directly above the club, it only shares the main wall.

And yes, it is a small but loud club (live rock music and stuff) and there is not much soond proofing wrt the walls. The wall in question is one of the main walls which holds the whole buliding, more than two feet thick. When I hold my ear against it I can actually hear people's conversations. I'm personally involved with the club (I do all the technical stuff, and the live mixing at times) so the noise is not an issue for arguments.

Of course I didn't intend to generalize this single isolated experience....

- Klaus

You are saying that a two foot thick brick wall conducts voice frequencies effectively? That just doesn't sound right. Is the center of the brick wood?

[y8s]

Originally posted by gedlee



You are saying that a two foot thick brick wall conducts voice frequencies effectively? That just doesn't sound right. Is the center of the brick wood?

In my brick-walled row house in Washington DC, I can hear conversations carried on by my abutting neighbors on both sides.

They, however, can't hear my home theatre subwoofer when it plays loud. I tested this myself by stepping into their house while it was supporting a party we were having. I couldn't hear the beat. I went back to the party.

Incidentally, science has recently suggested that, in some cases, high price makes an item desirable when contrasted to a similar low price version. I think it was a study of medicine or pills of some kind. Two similar (or same?) medications were offered--one at a very cheap price (a few cents per pill) and another offered (with the same indications) at a few dollars per pill.

People preffered the more expensive one because they imagined the higher price equated to higher effectiveness.

The public may not want a $200 Summa. They want a more effective $5000 Summa.

I'll coin a phrase here: What you get, you want to pay for.


Matt

[KSTR]

Originally posted by gedlee
You are saying that a two foot thick brick wall conducts voice frequencies effectively? That just doesn't sound right. Is the center of the brick wood?

No, it's really solid (I know as we made some cut-throughs, now supported with steel beams). Maybe it's really the type of brick that matters, those are clay ones which also have a very jingly high resonance when hitting them, holding it in your hand. My GF lives in a more modern building made from preconstructed concrete slabs and in her appartment you can literally hear every single word of the neighbours (or their radio/tv for that matter). I grew up in a all wooden house and I seem to recall much better isolation epecially for higher frequencies.

- Klaus (er, getting a bit too off-topic it seems)

[KSTR]

Originally posted by gedlee
What I have found works extremely well is to look at the spectrum of a sine waave as you drop the input signal level. If the higher orders of the spectrum rise, as they often do, then this would be a highly audible distortion - ie. crossover. The distortion that occurs at levels near clipping is pretty much irrelavent. And you can't look at THD + noise with level, because at the low levels all you will see is the noise. You have to note the levels of the harmonics themselves.


There was a post some time back on how I make this measurement. I have found that it tells me all that I need to know about electronics.

... and from what I could read in that thread and elsewhere I still seem to be the only one who has personally recreated your approach of this time-domain averaging with synced signals to lower the noise floor. It might be implemented in the professional measuring rigs like the most recent AP system, though.

- Klaus

[gedlee]

This thread is not the place to discuss noise control. I have done a substantial amount of noise control in both residential and automotive and what is being said here just does not jibe with my experiences. But enough on noise control. Another thread maybe.