Room help: measuring and treating a vaulted ceiling room

[sarumbear]

if you can fill the entire space above the bars in the ceiling with (acoustic) insulation material and then cover it with acoustically transparent fabric your room would be so good that your transition frequency would be around 100Hz or less.

What is “transition frequency”?

 

[abdo123]

What is “transition frequency”?

Roughly it's the room’s reverberation time in seconds by the volume of your room in cubic meters, then multiplying the square root of that sum by 2000.

 

[pozz]

Feel free to share more info on what you mean by isolation and how is it achieved.

I'm sure you've seen STC ratings for walls in acoustics guides. They say how much attenuation you can expect for a certain form of construction. But in practice those ratings are hard to achieve.

Mostly it's planning how much you need given what's on the other side of each wall. Plumbing for kitchen or bathroom, HVAC, noisy highway on one side, airway above. Controlling for leakage from doors, windows, vents, outlets. All stuff that's under the hood. Most difficult part seems to be preventing accidental coupling and reradiation back into the room.

What is “transition frequency”?

Schroeder frequency. A rough divide between modal and statistical regions of the room, the latter where speakers dominate sound, the former with the room. Where the acoustic wavelengths start to equal the room dimensions.

 

[sarumbear]

Roughly it's the room’s reverberation time in seconds by the volume of your room in cubic meters, then multiplying the square root of that sum by 2000.

May I have a reference to that please, if you have? Do you know any real world figures of example room/halls?

Could it be that you meant the Schroeder Frequency?

 

[abdo123]

I'm sure you've seen STC ratings for walls in acoustics guides. They say how much attenuation you can expect for a certain form of construction. But in practice those ratings are hard to achieve.

Mostly it's planning how much you need given what's on the other side of each wall. Plumbing for kitchen or bathroom, HVAC, noisy highway on one side, airway above. Controlling for leakage from doors, windows, vents, outlets. All stuff that's under the hood. Most difficult part seems to be preventing accidental coupling and reradiation back into the room.

Schroeder frequency. A rough divide between modal and statistical regions of the room, the latter where speakers dominate sound, the former with the room. Where the acoustic wavelengths start to equal the room dimensions.

I found the link where the absorption co-coefficients of most popular insulation material is calculated based on their densities. In case you're interested.

https://www.bobgolds.com/AbsorptionCoefficients.htm

 

[sarumbear]

Why are there discussions on insulation? The request is about acoustically treating the room.

 

[abdo123]

Why are there discussions on insulation? The request is about acoustically treating the room.

insulation material works as great cheap broadband absorbers (which is what you want instead of cheap foam).

 

[sarumbear]

insulation material works as great cheap broadband absorbers (which is what you want instead of cheap foam).

Not necessarily and often not. For instance standard fiberglass sheet is a bad absorber. I agree that cheap foam is not good but thick foam is better than most insulation materials.

 

[sarumbear]

The subject room needs diffusion then absorption, especially the rear wall.

 

[abdo123]

Not necessarily and often not. For instance standard fiberglass sheet is a bad absorber. I agree that cheap foam is not good but thick foam is better than most insulation materials.

Which is why i shared the link so people would know which material to buy

 

[sarumbear]

You are not getting my point. Neither of those absorbers in your table are suitable. Until you get to 4" mineral wool they are useless and very frequency dependant. By the time you somehow created a frame for the wool and cover it you are spending more money than a decent foam costs.

 

[abdo123]

You are not getting my point. Neither of those absorbers in your table are suitable. Until you get to 4" mineral wool they are useless and very frequency dependant. By the time you somehow created a frame for the wool and cover it you are spending more money than a decent foam costs.

Which foam do you suggest to treat the area between 200Hz to 2000Hz that is not useless until you hit 4"?

I'm genuinely interested because the only foam i know of that can work as a broadband absorber ( dense enough) is basotect, and that's a patented melamin foam that is ridiculously expensive.

 

[sarumbear]

Which foam do you suggest to treat the area between 200Hz to 2000Hz that is not useless until you hit 4"?

I'm genuinely interested because the only foam i know of that can work as a broadband absorber ( dense enough) is basotect, and that's a patented melamin foam that is ridiculously expensive.

As I said above. The subject room does not require wideband absorption. It is far too large to do that. You can only diffuse the reflections. The rear of the room is cavernous and we do not now how large it is. Unless you spend a lot of money you cannot reduce the reverberation time of that part of the room. There will always be reflections from there. You can however diffuse them.

I have outlined above what is the best course of action.

 

[abdo123]

As I said above. The subject room does not require wideband absorption. It is far too large to do that. You can only diffuse the reflections. The rear of the room is cavernous and we do not now how large it is. Unless you spend a lot of money you cannot reduce the reverberation time of that part of the room. There will always be reflections from there. You can however diffuse them.

I have outlined above what is the best course of action.

Forget about OP's room for a second, which type of foam would work better as broadband absorbers than fibrous insulation material?

 

[sarumbear]

Forget about OP's room for a second, which type of foam would work better as broadband absorbers than fibrous insulation material?

Any open-cell foam or porous fibre-based material works but the mechanical properties of the absorber panel is very important. You cannot simply stick foam to wall like you do with insulation and hope for the best. Foam works best because the mechanical properties are already in its shape.

 

[abdo123]

but the mechanical properties of the absorber panel is very important.

Please elaborate on what you mean by this.

 

[sarumbear]

Please elaborate on what you mean by this.

You cannot stick the insulation on a wall. You need to frame it somehow so that the edges are defined. You also need to cover it with something so that the fibres do not pollute the air. Now imagine if you covered it with a velvet cloth (as an extreme example). You have altered the absorption properties of the panel and not all frequencies will be absorbed the same. This will make the room sound odd as such enclosure properties do not normally exist in modern architecture.

 

[abdo123]

You cannot stick the insulation on a wall. You need to frame it somehow so that the edges are defined. You also need to cover it with something so that the fibres do not pollute the air. Now imagine if you covered it with a velvet cloth (as an extreme example). You have altered the absorption properties of the panel and not all properties will be absorbed the same. This will make the room sound odd as such enclosure properties do not normally exist in modern architecture.

So foam is better because it's idiot proof?

 

[sarumbear]

So foam is better because it's idiot proof?

Not really. a) not able to do DIY is not being an idiot b) you most likely will have a much better looking absorber

 

[tuga]

I have marked over your image and attached below.

Your main issue is the reverberation caused by ceiling, the rear wall and to a smaller extend by the floor. I can’t see the right wall (while sitting on the sofa) but the left slanting wall is perfect. You don’t need to do anything to that.

1- Trapezoidal hard partitions (marked yellow) that will split the ceiling will have the most effect to the sound.

2- Diffusion (not reflection) on the rear wall (marked red) will help to tighten the sound further.

3- Finally and much more simply, a thick carpet on the floor (marked green) will help.

As a side note, it seems you have tilted the centre speaker up a bit too much. You will be better of if you left it straight. You don’t want to excite the ceiling area.

In my opinion, filling the inside of the wooden trusses is a bad idea from an architectural point of view because it'll make the ceiling perceptually lower and the living space smaller, darker and somewhat oppresive.

Since the room is open to the lower floor there shouldn't be any serious issues with the bass.

Personally I would treat the sloped ceiling with light mid- and high-frequency absorption at least in the early reflection zones, add a thick long-haired carpet to tame the reflectiveness.

Diffusion on the staircase wall behind the sofa is a good ideia.