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Removing echo from an old classroom
Old 18th September 2012
  #1
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🎧 5 years
Removing echo from an old classroom

I hope you don't mind my asking a non-recording question about room acoustics. I work as a tutor for students who have dyslexia. The classroom where we have been assigned to work has terrible echoes that make it difficult for the students to hear exactly what we are saying and fore us to hear if the student is making a mistake. Being able for everyone to hear speech clearly is very important to us. The room is 36x23x12 with smooth plaster walls and ceiling, windows along one wall, and a slate blackboard along another. There is a picture rail along the top of the walls. We tutor in small cubicles in two corners of the room (standard business cubicles). As you might guess, there is little money to do anything substantial, perhaps under $500, and I doubt I can get the school to allow us to make any changes to the walls or ceiling.

1. Would it be feasible to treat just our small cubicle areas, or do we need to treat the whole room?

2. I've read differing points of view regarding the effectiveness of moving blankets like those from from U-Haul -- are they a waste of money, or would they provide some help? Would we be better off by saving our money until we can afford acoustical blankets or panels of some kind?

3. What percentage of the walls would we need to cover to make a significant improvement?

4. Is it better to place the treatments up high or at face level?

Thanks so much for any help you can give me. I really appreciate it!
Pete
Old 18th September 2012
  #2
JWL
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🎧 15 years
Generally for a situation like this you will want high frequency absorption more or less evenly scattered throughout the room, with enough coverage area to reduce reverb times to the desired level. If you know the current reverb time, you can calculate the amount of absorption you need for the room to get it down to where you want it, but honestly just trial and error works well. Start with as many panels as you can afford and see where you are. Moving blankets will help soak up some highs, but won't give you even reverb at all frequencies (you will need real acoustic panels for this).
Old 18th September 2012
  #3
Gear Head
 
🎧 5 years
Ear level is optimum but in your case I think you need to cover a lot of area. Packing blankets are so ugly and really thin. I would recommend a carpet remnant and some foam. A good, thick shag carpet on the floor in the cubicles would absorb a lot of reflections - if that's allowed. (8) 82" x 36" Open Cell/ Urethane-Ether Foam panels ($225.00) could be covered with fabric secured by hot glue and hung from the picture rail with string or wire. If you put 12" between every panel you could cover the entire 36' wall horizontally and half of it vertically.
I'm not an acoustician but I think this would do the trick and keep you under your budget.
I googled these guys for reference.
High Density Foam, Custom Cushions, Upholstery Foam, Cushion Replacement, Mattress Pad
Good luck!
Old 18th September 2012 | Show parent
  #4
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HermanV's Avatar
 
🎧 10 years
Quote:
Originally Posted by jwl ➑️
Generally for a situation like this you will want high frequency absorption more or less evenly scattered throughout the room, with enough coverage area to reduce reverb times to the desired level. If you know the current reverb time, you can calculate the amount of absorption you need for the room to get it down to where you want it, but honestly just trial and error works well. Start with as many panels as you can afford and see where you are. Moving blankets will help soak up some highs, but won't give you even reverb at all frequencies (you will need real acoustic panels for this).
OP, Where are you located?
you might be able to make some DIY sound absorption panels for a good price if you are in the US. (I am not sure about prices in other countries). With your budget I would also, as mentioned, start treating the room with 2" thick 2x4 panels spaced out along the walls of the room and also, if possible, mounting some on the ceiling. Little things like hanging some thick curtains for the window areas and a couple of rugs on the floor will all help shorten the decay times of the echo and improve speech intelligibility in the classroom.
Old 19th September 2012 | Show parent
  #5
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🎧 5 years
Quote:
Originally Posted by HermanV ➑️
OP, Where are you located?
I'm in Wisconsin.

Would it be necessary to treat the entire room, or could we just treat the small cubicle areas where we work with the students? We are typically working right across a small table from them, so it would nice if we didn't have to treat the whole room.
Old 19th September 2012
  #6
Deleted 56021e5
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you need to find fire rated solutions. This is a public space ! Not your control room.


Check melanine foam. Cover at least half of the ceiling. You might have to treat also the walls if needed afterwards500 bucks wont be enough for this I am afraid.

I know what I am talking about since I do treat classrooms often
Old 19th September 2012
  #7
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🎧 10 years
depending on the type of cubicles, it may be better to extend them up then add some fire rated absorption over top - perhaps even a cubicle wall panel suspended down from the ceiling - depends on the lighting needed as well.

you could also look into acoustic ceiling tiles as a means of doing this.

also, as this is a classroom, you might check into the laws requiring certain acoustic properties for classrooms and see if the school can obtain proper services and work to improve the room. this may be easier also considering this may fall under special education funding.
Old 19th September 2012 | Show parent
  #8
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HermanV's Avatar
 
🎧 10 years
Quote:
Originally Posted by pduck ➑️
I'm in Wisconsin.

Would it be necessary to treat the entire room, or could we just treat the small cubicle areas where we work with the students? We are typically working right across a small table from them, so it would nice if we didn't have to treat the whole room.
The fabric I use is treated with fire proofing material as well as the mineral wool. If you choose to DIY just make sure you buy safe materials and that everything is nice and secure when mounted.

I would say for you treat the entire room but with more focus towards the walls and ceiling where the cubicles are and then whatever money is left over you can treat other areas. maybe add some rugs and curtains to those windows to reduce the flutter.
Old 19th September 2012
  #9
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🎧 10 years
you would be amazed at how much improvement can be made from using book shelves full of books.

acoustic ceiling tiles are well worth it. armstrong is a company that produces ceiling tiles. the tiles are specifically design for office/speech situations.

carpet on the floor is also a good thing.

you can also buy desk dividers that have an acoustic ratng
Old 19th September 2012 | Show parent
  #10
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HermanV's Avatar
 
🎧 10 years
Quote:
Originally Posted by gullfo ➑️
depending on the type of cubicles, it may be better to extend them up then add some fire rated absorption over top - perhaps even a cubicle wall panel suspended down from the ceiling - depends on the lighting needed as well.

you could also look into acoustic ceiling tiles as a means of doing this.

also, as this is a classroom, you might check into the laws requiring certain acoustic properties for classrooms and see if the school can obtain proper services and work to improve the room. this may be easier also considering this may fall under special education funding.
+1 That is an excellent solution. The school should find the means to fund such a project. I built a couple of panels for a school and they even had their own guy pick up the panels in a district van. he was going to install them as well.
Old 19th September 2012 | Show parent
  #11
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Carpet on a classroom means trouble... first because it is a pain in the ass to clean it ! :-))

The floor can be reflective as long as the ceiling and eventually the walls are treated !




Quote:
Originally Posted by gouge ➑️
you would be amazed at how much improvement can be made from using book shelves full of books.

acoustic ceiling tiles are well worth it. armstrong is a company that produces ceiling tiles. the tiles are specifically design for office/speech situations.

carpet on the floor is also a good thing.

you can also buy desk dividers that have an acoustic ratng
Old 19th September 2012 | Show parent
  #12
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🎧 10 years
Quote:
Originally Posted by andrebrito ➑️
Carpet on a classroom means trouble... first because it is a pain in the ass to clean it ! :-))

The floor can be reflective as long as the ceiling and eventually the walls are treated !
what the.

have you ever designed a classroom, library, lecture theatre.

getting back to the op's question,

just treating the cubicle should make a difference, depends on whether the echo is from your speech or noise sources within the room itself. moving the cubicles away from the corners/walls will also help.
Old 20th September 2012 | Show parent
  #13
Deleted 56021e5
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I am not kidding, yes I did... tons of them.. I work often in building acoustics. I have done dozens of schools where I live. The question is have YOU ever done this kind of work with architects ? Or with other engineers of other areas such as energy, HVAC etc?

Say to them you are going to use carpet in a classroom and they laugh in your face. ! Carpet on public spaces is a no-no where I live. The architects hate them, it deteriorates much more than other materials. It is a mess to clean it. Sure it works fine in an office. On a school there are way better solutions. It is much easier to use an hard floor and place absorption on the ceiling.

Here only industrial carpets are allowed on schools. It is rarely used in schools nowadays. It was maybe 20-30 years ago.


Quote:
Originally Posted by gouge ➑️
what the.

have you ever designed a classroom, library, lecture theatre.

getting back to the op's question,

just treating the cubicle should make a difference, depends on whether the echo is from your speech or noise sources within the room itself. moving the cubicles away from the corners/walls will also help.
Old 21st September 2012
  #14
Here for the gear
 
🎧 5 years
OP here.

I'm getting some great ideas! My director gave the go ahead on the project, provided that everything is removable. We are only renting the space, so ceiling tiles would be out of the question. But the idea of extending the cubicle upward was interesting. If I placed 4x8 sheets of plywood vertically against the cubicle walls, it would essentially make the cubicle 8' high (in a room with 12' ceilings) with an 8x8' floor space. If I hung sound blankets on the plywood walls and hung acoustical panels on the other walls of the cubicle, would that make enough of a difference to make speech intelligible? Or would the "roof" of the cubicle need to be closed off with absorbant material also?

Thanks
Old 21st September 2012 | Show parent
  #15
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🎧 10 years
yes mate, architecture is my day gig, has been for many years now.

plenty of educational projects under the belt and all involved acoustic engieers as well as carpet.

even a couple where carpet was added because the acoustic and comfort levels were woeful.

i guess different countries have different solutions though.

commercial grade capret is the only choice with that kind of work, a) it's fire rated, b. it's tuff. it's good for seveal years at which point it's stripped out and replaced. if high wear levels are expected then carpet tiles are specified.





Quote:
Originally Posted by andrebrito ➑️
I am not kidding, yes I did... tons of them.. I work often in building acoustics. I have done dozens of schools where I live. The question is have YOU ever done this kind of work with architects ? Or with other engineers of other areas such as energy, HVAC etc?

Say to them you are going to use carpet in a classroom and they laugh in your face. ! Carpet on public spaces is a no-no where I live. The architects hate them, it deteriorates much more than other materials. It is a mess to clean it. Sure it works fine in an office. On a school there are way better solutions. It is much easier to use an hard floor and place absorption on the ceiling.

Here only industrial carpets are allowed on schools. It is rarely used in schools nowadays. It was maybe 20-30 years ago.
Old 21st September 2012 | Show parent
  #16
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HermanV's Avatar
 
🎧 10 years
Quote:
Originally Posted by pduck ➑️
OP here.

I'm getting some great ideas! My director gave the go ahead on the project, provided that everything is removable. We are only renting the space, so ceiling tiles would be out of the question. But the idea of extending the cubicle upward was interesting. If I placed 4x8 sheets of plywood vertically against the cubicle walls, it would essentially make the cubicle 8' high (in a room with 12' ceilings) with an 8x8' floor space. If I hung sound blankets on the plywood walls and hung acoustical panels on the other walls of the cubicle, would that make enough of a difference to make speech intelligible? Or would the "roof" of the cubicle need to be closed off with absorbant material also?

Thanks
How big is the gap between the cubicles? If you were to cut the 4x8 sheets into 3x8 you could built lightweight panels out of 1x2 that can rest on top of the plywood from both ends of the cubicles and then secure the panel with L brackets onto the plywood. I have built a couple of panels that rest on these types of frames. However, If you extend the cubicles that high and place absorbent material on the plywood then you will essentially break up the reflections of the room and there will be a lot of improvement this way so my idea of treatment on the ceiling might just be overkill.
Old 21st September 2012
  #17
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🎧 10 years
if they are commercial cubicle products, you should be able to get more panels and stack them. if not 8' then 6' easily. the plywood with blankets - besides aesthetics - may not be fire rated and you need to stabilize the panels. maybe another option is to add a frame and hang fire treated blankets/"baffles".
Attached Thumbnails
Removing echo from an old classroom-cubicle-extensions-1.jpg   Removing echo from an old classroom-cubicle-extensions-2.jpg  
Old 21st September 2012
  #18
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1 Review written
🎧 5 years
I think stacking the acoustical panels, if you can find more of them, is the best idea so far in this thread.

Schools get fire inspections. The inspectors could go ape over any DIY stuff and make you pull it out just because it doesn't have a bunch of labels on it saying it meets this standard or that standard.

I'd shop around for acoustical cubicle panels --at office supply stores, on line, CL, wherever. If the school is paying, then it probably makes sense to try to find out what office supply place they use.

There's probably a bunch of the same thing sitting unused in some other school in the district.....
Old 21st September 2012 | Show parent
  #19
Deleted 56021e5
Guest
If the acoustics confort is awful usually is because the ceilings and walls are not well treated.

Carpet introduces a "wrong" absorption in the room where highs are absorbed but mid high, mid and lows are not. Carpet is a very unbalanced and poor absorber.

This is one of the reasons we don't use carpet on tracking and control rooms.

Now in a class room the most important octaves to absorb are from 500 to 2000 Hz but it is still beneficial to have absorption at 125 and 250 Hz.

Therefore what makes sense is to use absorption on the ceiling, as thick as possible or with an air cavity behind, which is quite common in some solutions. Also treating the walls could be important if the room is too reflective.

Carpet is really an old fashion and "bad" acoustical solution that could only be approved to minimize costs or due to constructive limitations.

Quote:
Originally Posted by gouge ➑️
yes mate, architecture is my day gig, has been for many years now.

plenty of educational projects under the belt and all involved acoustic engieers as well as carpet.

even a couple where carpet was added because the acoustic and comfort levels were woeful.

i guess different countries have different solutions though.

commercial grade capret is the only choice with that kind of work, a) it's fire rated, b. it's tuff. it's good for seveal years at which point it's stripped out and replaced. if high wear levels are expected then carpet tiles are specified.
Old 21st September 2012
  #20
Deleted 56021e5
Guest
Check melanine foam, it is usually fire ********. 30 mm would be fine for the 500-2000 Hz range and usually it is white color
Old 22nd November 2014
  #21
Here for the gear
 
🎧 5 years
hello,
I am new here, I just want to ask if any of you knows about online diploma for related to acoustic or noise and vibration control distance learning. My current location is here in Abu Dhabi, United Arab Emirates I am looking forward to my career path to acoustic. Any recommendation a website.I appreciate you help..

thanks,
Andy
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