Outside Effect Of A Treated Room

[SoSueMe]

I've never done any measurements on this, but have always been curious...

If I were to add significant bass trapping, broadband absorption, and diffusion in a typical 2nd-level bedroom that's approximately 13W x 12D x 9H, how would this effect the sound outside the room (both inside and outside of the house)? Would there be any change?

The initial goal is not to effect the outside, by the way, although I may find later the outside levels to be bothersome, which will need to be taken care of.

[Glenn Kuras]

Not enough to make any kind of "sound proofing" difference.

[SoSueMe]

Yes, that's why I didn't say those words (sound proofing). I'm just wondering if the sound would change, if at all.

Thanks.

[avare]

Originally Posted by SoSueMe

Yes, that's why I didn't say those words (sound proofing). I'm just wondering if the sound would change, if at all.

Minimal change outside the room. Possibly more sound.

Andre

[dainja]

I believe the experts here and I know acoustics is a complex topic but I'm curious too... Wouldn't broadband absorbers placed in front of flanking paths reduce some high end sound transmission, at the very least?

Like, if ductwork running through a room is a weak point in terms of isolation, and 4" of 703 was placed in front of the ductwork, it would make sense that this would be a sound barrier of sorts...?

Again, I'm basing this entirely on assumptions and have very little experience with isolation.

[SAC]

One might wonder why we tend to dismiss and occasionally find humorous the erroneous confusion of the use of sound transmission/isolation techniques to someone effect beneficial changes within a room.

But when the converse is considered, and the internal acoustical treatment is the focus, then suddenly its impact on sound isolation and transmission suddenly assumes a viable - and serious - source of considerable consideration.

But then... considering that most treatment is oriented at frequencies where there is only moderate energy content while other lament the fact that NRC and STI figures are of limited use to the full range of music frequencies where much greater energy content abides...

[avare]

Originally Posted by dainja

Like, if ductwork running through a room is a weak point in terms of isolation, and 4" of 703 was placed in front of the ductwork, it would make sense that this would be a sound barrier of sorts...?

You are asking a different question from OP. 4" of 703 directly in the path of the sound will have a transmission loss (TL in acoustics speak) similar to curve c in fig 2 of the USG document I linked in this thread. The TL of 703 is not suficient for any meaningful sound isoaltion. How is the duct going to function if it is blocked?

Andre

[SoSueMe]

I know, first hand, the benefits of a well-treated room. I just find it interesting how such a profound effect within the treated room would have little or negligible effect outside the room.

I'm guessing the reason is that the internal treatment has little effect on what gets transmitted to the perimeter walls, which will continue to act as reproductive devices themselves, as heard from outside the room.

Conversely, I'd imagine that a very absorptive room would sound different than the same room with no absorption from outside of the room IF a large part of what you are hearing wasn't from architectural transmission (i.e. sound escaping from underneath a door, for example).

[avare]

Originally Posted by SoSueMe

I'm guessing the reason is that the internal treatment has little effect on what gets transmitted to the perimeter walls, which will continue to act as reproductive devices themselves, as heard from outside the room.

Bingo! Another factor is that as the gets more absorbent, the power required to attain a given SPL increases. This was discused in some detail in apaper by John Storyk about a nightclub designed by his firm in Switzerland. The story was treating the sound inside the nightclub and noise complaints increasing after the treatment. Noise surveys comparing before and after d clearly showed the increase.

Andre

[dainja]

Originally Posted by avare

You are asking a different question from OP. 4" of 703 directly in the path of the sound will have a transmission loss (TL in acoustics speak) similar to curve c in fig 2 of the USG document I linked in this thread. The TL of 703 is not suficient for any meaningful sound isoaltion. How is the duct going to function if it is blocked?

Andre

Thanks for that information! Its a bit fascinating actually!

I meant an actual duct going through the studio, feeding the rest of the building (rather than a vent)exact fact, that's exactly what I have in mine :p

[avare]

Originally Posted by dainja

I meant an actual duct going through the studio, feeding the rest of the building (rather than a vent)exact fact, that's exactly what I have in mine :p

Understood now. Yes it will help with the breakout and breakin noise.

Andre