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Forum index » Science and Technology » Physics » Acoustics
Room acoustics for piano.
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Todd A. Anderson
science forum beginner


Joined: 12 Jun 2006
Posts: 2

PostPosted: Mon Jun 12, 2006 10:42 pm    Post subject: Room acoustics for piano. Reply with quote

Hi,

I'm looking for suggestions on how to cheaply improve the acoustics
of my living room to make it suitable for a piano. Below is a diagram
looking side-on at a portion of my house.

~ 40 ft.
-------------------------------------------------------------
8 |
|
f |
|
t | L O F T L I V I N G
|
.. |
|
------------------------------- R O O M |
20 ft. 9 |
|
f |
|
t |
|
. |
|
------------------------------
20 ft.

As you can see, the living room is open to the 2nd floot ceiling.
The loft has a railing to prevent you from falling into the living
room. The depth of this space that you can't see if this diagram
is around 16 feet.

I don't know how to exactly describe the problem but after a
hand clap, you'll hear a high-pitched ping for a short period of
time. Both rooms are carpeted except for a portion of the
living room which has laminate flooring. There are two curtain
panels downstairs in the living room and a couch. The space
is also bad for localization. Someone can shout to you from the
other side of the house and they can sound like they are coming
from a completely different direction.

From what I've read, the solution seems to be some degree of
foam on the walls but how do you know how much you need
and where to place it? Also, aesthetics are important so how
do you make the foam look attractive? I've seen ones covered
in fabric. How would one go about constructing fabric covered
panels on their own?

thanks,

Todd
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Ethan Winer
science forum beginner


Joined: 08 Jun 2005
Posts: 37

PostPosted: Tue Jun 13, 2006 4:51 pm    Post subject: Re: Room acoustics for piano. Reply with quote

Todd,

Quote:
I'm looking for suggestions on how to cheaply improve the acoustics of my
living room to make it suitable for a piano.


Your room is certainly large enough to get a good sound, so the main focus
should be on avoiding reflections from nearby surfaces and, assuming the
room is too live generally, adding absorption elsewhere around the room to
reduce the overall reverb time.

You can do this cheaply using two inch thick rigid fiberglass wrapped in
fabric. If you also use the room for playing music through a stereo you
might consider doing more than the minimum. For full range music you'll want
rigid fiberglass four inches thick, and some of it should be placed near the
room corners.

Quote:
Both rooms are carpeted except for a portion of the living room which has
laminate flooring.


Pianos generally sound best on a reflective floor, not carpet.

Quote:
aesthetics are important

There's a saying among acoustic treatment vendors: "You can have effective,
cheap, or attractive. Pick any two." :->)

Quote:
How would one go about constructing fabric covered panels on their own?

You buy a bunch of 2 by 4 foot rigid fiberglass panels, you buy fabric and
spray glue, and you wrap the panels with the fabric using the spray glue to
hold it in place. If you're not handy, there are a number of companies that
sell finished panels. Search Google for Acoustic Treatment and you'll get
many links. My Acoustics FAQ should pop up near the top of the list, and it
has a lot of advice for DIY'ers that's easy to read with no math. You'll
probably come across a link to my company RealTraps as well.

--Ethan
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Todd A. Anderson
science forum beginner


Joined: 12 Jun 2006
Posts: 2

PostPosted: Tue Jun 13, 2006 6:10 pm    Post subject: Re: Room acoustics for piano. Reply with quote

Quote:
There's a saying among acoustic treatment vendors: "You can have
effective,
cheap, or attractive. Pick any two." :->)

Cheap and attractive please. Smile Room doesn't have to be acoustically
perfect just significantly better than it is now.

Quote:
How would one go about constructing fabric covered panels on their own?

You buy a bunch of 2 by 4 foot rigid fiberglass panels, you buy fabric and
spray glue, and you wrap the panels with the fabric using the spray glue
to
hold it in place. If you're not handy, there are a number of companies
that
sell finished panels. Search Google for Acoustic Treatment and you'll get
many links. My Acoustics FAQ should pop up near the top of the list, and
it
has a lot of advice for DIY'ers that's easy to read with no math. You'll
probably come across a link to my company RealTraps as well.

Define "a bunch." Can you combine 3 or 4 of these panels together before
wrapping with fabric or does that significantly decrease their
effectiveness?

Thanks again for your help.

Todd
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Chris Whealy
science forum addict


Joined: 05 May 2005
Posts: 54

PostPosted: Tue Jun 13, 2006 9:09 pm    Post subject: Re: Room acoustics for piano. Reply with quote

Absorption will help in so much as it will attenuate the volume of
certain frequencies. However, any given depth of fibre glass or
Rockwool will absorb frequencies down to certain point, but below that,
the bass frequencies will still persist. Often what happens after
absorption is put up is that the echo you described is not completely
removed, it is just lowered in pitch. This is because the absorber is
very effective at removing frequencies over 1 KHz (typically), but much
less effective for frequencies below that point. The net result is that
you remove any high frequencies from the echoing sound, but retain the
low frequency components - hence the lowering in pitch of the echo.

What I have found to be very effective (and very cheap to implement) is
the use of diffusion. The simplest way to implement diffusion is to go
to your local carpet or textile supplier, and ask them if you can
have/buy any old cardboard tubes that the fabric or carpet was wrapped
around. These will be about 8' long and as long as they are 8" or more
in diameter, they will work fine.

Get about 10 or 15 of these tubes (a range of diameters up to 16" would
also be good) and cut them in half along their length, and then simply
stand them up against the walls with the convex side facing outwards.
You should notice an immediate removal of any obtrusive echoes, and an
overall smoothing out of the sound in your room(s).

This is such a simple way of scattering sound, that many people dismiss
it as being too simple - but try it, it works! The cardboard tubes are
simply a cheap and effective way of proving to yourself that diffusion
helps the overall sound. Once you have proven the concept, you can
create the diffusion using any means you like that will fit with the
aesthetics of your room.

The point here is not that you need to use cardboard tubes, but that
sound reflections are broken up by objects protruding into the room.
This is why many concert halls built in the 19th century have such good
acoustics - just look at the number of ornate plaster mouldings they
contain. These objects provide a high degree of diffusion.

You could use any shape you like really, as long as it breaks up the
reflection and scatters the sound. The cardboard tubes are cheap and
easy to come by; so demonstrate to yourself that what I'm saying
actually works, then implement the principle in whatever way is
appropriate for your room.

Regards

Chris W

--
The voice of ignorance speaks loud and long,
But the words of the wise are quiet and few.
---
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Ethan Winer
science forum beginner


Joined: 08 Jun 2005
Posts: 37

PostPosted: Wed Jun 14, 2006 6:03 pm    Post subject: Re: Room acoustics for piano. Reply with quote

Todd,

Quote:
Cheap and attractive please. Smile

It's all in my acoustics FAQ:

www.ethanwiner.com/acoustics.html

Part of "cheap" also means you must be willing to do a little leg-work on
your own. In this case, willing to read up a little.

Quote:
Define "a bunch."

How many you need depends entirely on the size of the room. A room like
yours that's 40 feet long will need a fair number of panels. At least 10 I'd
say. You could focus more around where the piano is, but if you treat ONLY
that place you'll still have audible echoes bouncing around the rest of the
room.

Quote:
Can you combine 3 or 4 of these panels together before wrapping with
fabric or does that significantly decrease their effectiveness?


As Chris explained, when the panels are thicker (more layers), they absorb
to a lower frequency. But that increases their surface coverage only
slightly. So to do the full range you need thick panels - four inches is
good - AND you need a "bunch" of them.

--Ethan
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Angelo Campanella
science forum Guru Wannabe


Joined: 08 May 2005
Posts: 226

PostPosted: Wed Jun 21, 2006 6:27 am    Post subject: Re: Room acoustics for piano. Reply with quote

Todd A. Anderson wrote:
Quote:
I don't know how to exactly describe the problem but after a
hand clap, you'll hear a high-pitched ping for a short period of
time. Both rooms are carpeted except for a portion of the
living room which has laminate flooring.

I have heard room rings in the past. They are indeed weird. They are,
in my opinion, a trapped wave between two fairly close parallel
surfaces, or combination of surfaces. The only way to hunt them down is
to apply a small panel, e.g. a 4'x4' piece of rigid fiberglass ("Duct
liner board") temporarily on various wall surfaces, perhaps high; in the
vicinity of the loft. Eventually you will find a location where the
panel that will suppress the ring. Then you install just enough panel
area to suit your taste (degree of ring suppression).

Quote:
There are two curtain
panels downstairs in the living room and a couch. The space
is also bad for localization. Someone can shout to you from the
other side of the house and they can sound like they are coming
from a completely different direction.

That means that high reflections dominate the reverberation. I once had
a client with such a loft that, while sitting in the living room, was
annoyed by conversations in the entrance foyer, or in the kitchen. I
recommended he hang baffles or short drapes from the loft ceiling to
intercept the central ceiling reflection.

Such geometric reflections are treated in commercial spaces by always
having an acoustical tile ceiling. But that would result in too dead a
speace for piano music.

Quote:
From what I've read, the solution seems to be some degree of
foam on the walls but how do you know how much you need
and where to place it? Also, aesthetics are important so how
do you make the foam look attractive? I've seen ones covered
in fabric. How would one go about constructing fabric covered
panels on their own?

Another method is to stretch any desired fabric over a frame. The frame
is just wood sticks that are arranged into a rectangle, fastened to the
wall. The depth of the cavity behind the fabric, determined by the
frame material thickness, should be 1" to 2" (25-50mm). The fill behind
the fabric may be duct liner board. It's tricky to make a neat job (to
keep the fabric taut without lumps of absorber showing). You could also
use a heavier upholstery cloth, and leave the cavity bare.

You made no mention of the reverberation time of your space. Sabine
determined early on that the ideal reverberation time for piano music is
1.25 seconds (for his ear). This is relatively long for home spaces.

It implies that you should use no more treatment than is necessary to
alleviate the "bad" effects you noted. This also means that you have to
do a lot of testing with one or two (or three) such 4'x4' panels and
then just install the panels where the best suppression is achieved
without any more absorption. It also implies that you may want to remove
some absorption, like use thinner curtains, or remove a carpet, once the
"bad" effects are quenched with strategically placed absorber panels.

Angelo Campanella
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