Need Help On Room Acoustics

The to main objectives of soundproofing are two
1. to avoid the music escaping into someone else's house as noise; they don't regard it as music any longer.
2. The second is to reduce the incidence of the echo, which causes sound interference.

The interference is what really screws up the music.

Then, once again, one has to see how much of the sound is below 50 dB, as most of this sound transmits through the structure of the building.

Prima facie, all that I can tell you now is that we have to define our objectives first, and then, proceed to procure materials and do the sound proofing.

It is also a common occurrence that after installing the sound proofing, you may actually screw-up the musical effects. One has to be a little careful when doing sound proofing. Of all the subjects in physics, sound and noise is one of the trickiest, i.e. to actually implement it in practice.

And, lastly keep away from Fiberglass !!!!!!
The bloody thing is dangerous.

The simplest way to go about it is to first seal the room acoustically.
Then you should see the direction of the propagation of the sound, usually in the direction the speakers are facing and provide wave-breakers. Shielding part of the wall is much less expensive than covering a whole wall.

I could also provide details of where to procure the materials, and the cost of the raw-materials starts around INR 8.00 per sqft ( Not in the range of INR 200.00 per sq ft).

If you want to save money, and i guess no one wants to spend money needlessly, you should do a soundproofing objective on paper first, finalize the schema, and then start the procurement of the materials.

And, at the cost of repetition,

Do Not use fiberglass, especially in your home !

Lastly, do not have, permanent installations of the soundproofing panels, as you may have to shift the panels around to get the desired sound quality. These could be made permanent after the locations are finalized.

A good way to start is first to first do the sound proofing i.e. to completely stop the sound escaping from the room. play the music at your desired level, and go to you neighbour's house and physically check if there is any disturbing sound. There no bigger screw-up than an irritated neighbour knocking at your door when you are really enjoying your favourite music at the desired volume.

Phew, I could write a book on this.

Then you should make absorber blocker panels, 1Mx1M and install them at stretegic places in the room. One should make these panels properly as they look very ugly.

In this manner, you would have cut out about 80% of the echo sound. Once the echo is reduced to the maximum. Then you could begin to really enjoy the music.

lastly, with a little ingenuity, One can reduce the costs drastically.
 
Sridar, Thanks for your post.

Then, once again, one has to see how much of the sound is below 50 dB, as most of this sound transmits through the structure of the building.
More explanation on this please. I think you meant 50 Hz but typed dB. How can we control structural transmissions considering houses in India are built using concrete and steel? For me, my HT room is on the first floor and structural vibrations can be heard and felt in atleast one other room below.

Of all the subjects in physics, sound and noise is one of the trickiest, i.e. to actually implement it in practice
Add fluids to your list. Very difficult to predict and control under some circumstances.

And, lastly keep away from Fiberglass !!!!!!
The bloody thing is dangerous.
You are absolutely right on this aspect. But has it been proven that Fibreglass is carcinogenic?

provide wave-breakers
What exactly are these? Diffusors?

Phew, I could write a book on this..
You should:)
 
Oops Santosh,
You are right, I meant 50 Hz.

I would have to study the matter further.

For a sub-woofer, the best position is to have it down-firing ( in my opinion ), and that is where it would transmit the maximum sound. One has to physically isolate the subwoofer from its base support.
If you put a foam, or a sound dampener at this location, it would screw-up the sound. I would have to experiment with noise-isolating-metal-laminates, and hard rubber mounts. This should eliminate the structure-transmitted sound by around 60%.

Fiberglass is not carcinogenic. Over time, and with the vibration, the fiber crumbles and forms fine dust, which can easily get airborne. This usually gets inhaled, and lodges itself in the lungs. It is, in a manner of speaking, bio-degradable, but the degradation takes a very long time. If one inhales, a slightly larger quantity, the fibres are lodged in the the throat, or in the vocal chords.
the long and short of it is that, it is best to avoid the use of fiberglass. It is to be used only as a last resort, when other solutions are not possible.
 
can anyone tell me how I can put an image in here

I have an image of a wave-breaker, which i want to put in here
 
Fiberglass is not carcinogenic. Over time, and with the vibration, the fiber crumbles and forms fine dust, which can easily get airborne. This usually gets inhaled, and lodges itself in the lungs. It is, in a manner of speaking, bio-degradable, but the degradation takes a very long time. If one inhales, a slightly larger quantity, the fibres are lodged in the the throat, or in the vocal chords.
the long and short of it is that, it is best to avoid the use of fiberglass. It is to be used only as a last resort, when other solutions are not possible.
Very well written explanation Sridar. Thanks.
 
You are right once again. Proper sound insulation has to be built into the architecture of the building structure. Once again, we really cannot do anything about the building structure, so we have to physically isolate the transmission of the low-frequency noise. Again, this would result in a compromise solution.
 
Close up of a sound wave breaker. This kind of foams, coupled with blockers, whould be made into panels and installed.
 
can anyone tell me how I can put an image in here

I have an image of a wave-breaker, which i want to put in here
Here is a pictorial guide on posting images on HFV:
http://www.hifivision.com/announcements/1091-how-post-image-hifivision-com.html

You are right once again. Proper sound insulation has to be built into the architecture of the building structure. Once again, we really cannot do anything about the building structure, so we have to physically isolate the transmission of the low-frequency noise. Again, this would result in a compromise solution.
If I build a house again, the Home Theater will be in the basement. The problem (not really a pain point but would like to fix it) that I am facing is to do with structural vibrations being transmitted. The LFs can be felt in the room below.
 
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You would have the highest transmission of structure borne vibration if your HT were in the basement. ( I reaallysish noise engineering was simpler ). It would be something like shaking you from the foundation.
The noise source has to be physically isolated from the structure. Any physical contact would transmit the noise. And there has to be some physical contact. We have to endeavour to reduce the transmission of the noise/sound as much as possible.
 
Sridar,

please check post #35. This post contains the how safe the each of the material like rockwool, fibreglass and organic like cotton and Jute. Surprisingly Cotton and Jute when inhaled are more dangerous than the other two.

This post says the sceintific study on people who worked in those industries and experiments were conducted on rats.

I agree that continous contact with these materials is a problem, By making panels and closing them are we really in contact with them regularly.

thanks
Pandu
 
Hey Pandu,

I am into soundproofing.
Fiberglass, is best avoided !

You need not get into fibres at all, when there are foams and polymer blockers available.

I agree with you. Any kind of fibre, organic or inorganic, is harmful.

Warmest regards
Sridar
 
Sridar, there are products available in US where it is possible to de-couple the floor from the walls. Using those we can fully achieve a "room in a room" but are very expensive.

You would have the highest transmission of structure borne vibration if your HT were in the basement.
Sridar, my idea of a basement HT was also with a view to isolate the vibrations. Correct me if I am wrong....when the foundation is built, there is soil in between four walls (ie., before you cover it with flooring of some sort). So, it is easiest at this stage to isolate the floor from the foundation/walls.

I reaallysish noise engineering was simpler
Very True indeed. It is very interesting though.
 
Principles of sound-proofing are.
1. Seal the entire room -
2. Put the maximum number of absorber blockers.
3. kill the echo wave.
4. kill the standing wave.

Thassit
 
dear Santosh

Yes you have to use de-couplers. None the less, there would be some transmission of the vibration. I have samples of de-couplers with me.

You have to reduce the transmission of sound at every stage. Sub to floor, wave to floor/walls, speaker holders to the walls etc etc.

on the topic of putting the HT in the basement.
This would be like providing vibration to a cantilever(building) at its base. the base is wherein the vibrations would be pulled into the structure (max). the vibration has nowhere else to transmit or be damped.
soil is not the issue. When you are putting the HT into a room you are already transmitting the vibration to the structure. One would have to de-couple the grouting walls and the building structure.

Sridar
 
Fiberglass is not toxic, really. It poses a risk of long-term hazard, and is is an extremely undesirable product for home-use.
You should be using foams with a surface porosity, and with an uneven surface finish, preferably a pyramid surface-finish (about an inch-high pyramids).
These foams should have an acrylic backing as a sound blocker.
The ideal would be a foam-blocker-foam combination.

You could take a 2" polyurethane foam and gouge out pyramids 1 inch high. This would leave 1 inch of pyramids and 1 inch of foam. have a polymer backing behind it even 2 mm would be ok. and have a half inch denser foam behind it.
 
How do we get around flakes becomming airborne. Maybe I can cover the panels with non porous material like plastic sheet from all sides.

Result: Bass will not be an issue. Highs could get bright.
 
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