I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

Thanks.

Fleemo wrote:
I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

Thanks.

If you want a vocal booth, the cheapest way I have ever heard of it
being done is with a simple wooden frame and a few thick blankets.

Ian

Fleemo,

I saw inexpensive foam mattress pads

Those are not useful because they're not made of real acoustic foam.

Ian's suggestion to use heavy blankets is good, and even better is to make
panels from rigid fiberglass. You can buy 5/8 inch ceiling tiles made of
rigid fiberglass at Home Depot.

--Ethan

On Sat, 11 Sep 2004 16:02:30 -0400, Fleemo wrote
(in article ) :

I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

Thanks.

If you like the sound of a small, dead space, yes.

Regards,

Ty Ford





-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

On 11 Sep 2004 13:02:30 -0700, (Fleemo) wrote:

I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?


It might make a small, dead space. Or you could take a microphone
under your duvet. Probably sound just the same, and be only slightly
less pleasant to sing in ;-)

i suggest you record vocals in the best-sounding space in your house,
not design a bad-sounding one.

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

Fleemo wrote
.... Would this make a decent soundbooth?

For what purpose?

Laurence Payne wrote:
On 11 Sep 2004 13:02:30 -0700, (Fleemo) wrote:


I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?



It might make a small, dead space. Or you could take a microphone
under your duvet. Probably sound just the same, and be only slightly
less pleasant to sing in ;-)

Depends when the duvet was last washed ;-)


i suggest you record vocals in the best-sounding space in your house,
not design a bad-sounding one.


For vocals you generaly want the deadest space you can achieve so that
you have a clean uncoloured sound before you add electronic reverb/FX
to it. Sticking a singer under a few blankets/duvets is surprisingly
common.

Ian

"Ethan Winer" ethanw at ethanwiner dot com wrote in
:

Fleemo,

I saw inexpensive foam mattress pads

Those are not useful because they're not made of real acoustic foam.

Ian's suggestion to use heavy blankets is good, and even better is to
make panels from rigid fiberglass. You can buy 5/8 inch ceiling tiles
made of rigid fiberglass at Home Depot.

--Ethan




You can also use the rigid fiberglass panels used in making Air Conditioner
Ducts.

-Bruce

On Sun, 12 Sep 2004 18:29:46 +0100, ruffrecords
wrote:

For vocals you generaly want the deadest space you can achieve so that
you have a clean uncoloured sound before you add electronic reverb/FX
to it. Sticking a singer under a few blankets/duvets is surprisingly
common.

If you say so :-)

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

Laurence Payne wrote:
On Sun, 12 Sep 2004 18:29:46 +0100, ruffrecords
wrote:


For vocals you generaly want the deadest space you can achieve so that
you have a clean uncoloured sound before you add electronic reverb/FX
to it. Sticking a singer under a few blankets/duvets is surprisingly
common.


If you say so :-)


I did use the word 'generaly' to allow for exceptions. For most home
recordists who use an untreated bedroom for recording vocals, the make
it dead with a blanket method is most appropriate. Of course there
are some people and pro studios who have spaces with wonderful
acoustics in which vocals (or anything acoustic) can sound stunning
with a stereo mic setup. Unnfortunately most of us don't have one.

I have just been reading an article in Sound On Sound where an album
was recorded on a single mic (in mono). The band was mostly acoustic
but did include a regular drum kit (placed way off in the corner of
the room). The only thing they had real trouble with was the bass
which they had to DI.

Ian

Ian

Thanks for the input here, folks. Sorry, I failed to be specific
about its intended use, which would be to record voice-overs.

I'm not clear on the duvet idea. What, do you drape a blanket over
your head like a Halloween ghost while recording the voice-over?

The fiberglass sounds interesting, but whatever approach I take must
be removable and easily reassembled, as I can't dedicate the space to
a permanent soundbooth.

-F

Thanks for the input here, folks. Sorry, I failed to be specific
about its intended use, which would be to record voice-overs.

I'm not clear on the duvet idea. What, do you drape a blanket over
your head like a Halloween ghost while recording the voice-over?

The fiberglass sounds interesting, but whatever approach I take must
be removable and easily reassembled, as I can't dedicate the space to
a permanent soundbooth.

-F

"Fleemo" wrote in message
om...
I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

I assume you're wanting to create a dead space for recording without
coloration or resonances, but if you have a tiled bathroom, you might want
to try it (the reverbration characteristics of a tiled bathroom is a major
reason why folks sing in the shower :-)), the natural reverb is often quite
pleasing. You can even change the reverbration characteristics by hanging
blankets on the walls or parts of them. However, if you want dead, than do
as Ethan suggests and check his site, he has some very good info on room
acoustic treatment.

"Fleemo" wrote in message
m...
Thanks for the input here, folks. Sorry, I failed to be specific
about its intended use, which would be to record voice-overs.

I'm not clear on the duvet idea. What, do you drape a blanket over
your head like a Halloween ghost while recording the voice-over?

The fiberglass sounds interesting, but whatever approach I take must
be removable and easily reassembled, as I can't dedicate the space to
a permanent soundbooth.

Just build some lightweight wooden frames for the tiles and use screws or
hooks to put them together so that they can quickly be put together and
taken apart. You can stack them when not in use and thay won't take up much
space.

"Porky" wrote in message
...

Just build some lightweight wooden frames for the tiles and use screws or
hooks to put them together so that they can quickly be put together and
taken apart. You can stack them when not in use and thay won't take up
much
space.

I'd recommend velcro. The problem with hooks is that things can still move
and vibrate. Granted, you won't be that loud with voice overs, but you never
know what might start resonating on you.

Fleemo wrote:
Thanks for the input here, folks. Sorry, I failed to be specific
about its intended use, which would be to record voice-overs.

I'm not clear on the duvet idea. What, do you drape a blanket over
your head like a Halloween ghost while recording the voice-over?

Exactly

The fiberglass sounds interesting, but whatever approach I take must
be removable and easily reassembled, as I can't dedicate the space to
a permanent soundbooth.


You could make three panels, hooked or hinged together and just unhook
or fold them when not in use. I seem to remember someone used a
clothes horse for this once.

Ian

On 12 Sep 2004 22:29:13 -0700, (Fleemo) wrote:

Thanks for the input here, folks. Sorry, I failed to be specific
about its intended use, which would be to record voice-overs.

I'm not clear on the duvet idea. What, do you drape a blanket over
your head like a Halloween ghost while recording the voice-over?

The fiberglass sounds interesting, but whatever approach I take must
be removable and easily reassembled, as I can't dedicate the space to
a permanent soundbooth.


What is wrong with the vocals you are currently recording? Have you
tried recording in other spaces in your house? A long microphone
cable is very affordable :-)

You can record dry and then mess with it. Or you can set up
something that sounds good and put a mic in front of it. This isn't
necessarily impractical. And I see a welcome trend (back) to this way
of working.

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

"Jim Carr" wrote in message
news:1Ua1d.85739$yh.58345@fed1read05...
"Porky" wrote in message
...

Just build some lightweight wooden frames for the tiles and use screws
or
hooks to put them together so that they can quickly be put together and
taken apart. You can stack them when not in use and thay won't take up
much
space.

I'd recommend velcro. The problem with hooks is that things can still move
and vibrate. Granted, you won't be that loud with voice overs, but you
never
know what might start resonating on you.

Good idea, just be sure to get the extra strong variety, regular velcro may
not have enough grip strength.

On Sun, 12 Sep 2004 13:29:46 -0400, ruffrecords wrote
(in article ):

Laurence Payne wrote:
On 11 Sep 2004 13:02:30 -0700, (Fleemo) wrote:


I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?



It might make a small, dead space. Or you could take a microphone
under your duvet. Probably sound just the same, and be only slightly
less pleasant to sing in ;-)

Depends when the duvet was last washed ;-)


i suggest you record vocals in the best-sounding space in your house,
not design a bad-sounding one.


For vocals you generaly want the deadest space you can achieve so that
you have a clean uncoloured sound before you add electronic reverb/FX
to it. Sticking a singer under a few blankets/duvets is surprisingly
common.

Ian

Ian,

I really have big problems with that statement. Dead space is seldom linear.
Small dead space, when excited by a loud enough vocal (or any sound) can
still become quite resonant, thus imparting the telltale signs of a small
dead space. In fact, small spaces covered with acoustic foam actually sound
sort of spongy when excited enough.

I prefer a larger space that has been treated with a combination of
diffusion and absorption. The larger and better treated the space, the less
likely it is to resonate.

Regards,

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com

Wow, you guys are great. I really appreciate the input here.

I'll try experimenting with existing spaces around my house first, and
then move on to constructing a booth from there. The reason I was
exploring the booth idea in the first place is that I read the two
essential elements for recording good voice-overs are a dead room and
a great mic. If anyone would care to chime in with suggestions for a
good mic for under $500, I'd love to hear your input on that as well.


Thanks so much.

Ty Ford wrote:
On Sun, 12 Sep 2004 13:29:46 -0400, ruffrecords wrote

snip

For vocals you generaly want the deadest space you can achieve so that
you have a clean uncoloured sound before you add electronic reverb/FX
to it. Sticking a singer under a few blankets/duvets is surprisingly
common.

Ian


Ian,

I really have big problems with that statement.

That's fine, it was only my opinion. You are welecome to disagree.

Dead space is seldom linear.

Not sure what you mean by that - are you saying it is non-linear?

Small dead space, when excited by a loud enough vocal (or any sound) can
still become quite resonant,

If it is still resonant then surely by definition it isn't dead?

thus imparting the telltale signs of a small
dead space. In fact, small spaces covered with acoustic foam actually sound
sort of spongy when excited enough.

That I can relate to. Small spaces covered just in acoustic foam can
can suffer from reflections and resonances just like a big one except
the resonant frequencies will be much higher because the dimensions
are much smaller. I did not advocate using acoustic foam - someone
else did.


I prefer a larger space that has been treated with a combination of
diffusion and absorption. The larger and better treated the space, the less
likely it is to resonate.

No problem so long you you have access to one. Most home recordists
are limited to dong the best they can in a small room. In such
circumstances my preference would be for a simple frame covered with
heavy blankets.

Ian

Fleemo wrote:
Wow, you guys are great. I really appreciate the input here.

I'll try experimenting with existing spaces around my house first, and
then move on to constructing a booth from there. The reason I was
exploring the booth idea in the first place is that I read the two
essential elements for recording good voice-overs are a dead room and
a great mic. If anyone would care to chime in with suggestions for a
good mic for under $500, I'd love to hear your input on that as well.


Thanks so much.

When you say voice-overs do you mean talking or singing and are we
talking male or female voice?

Ian

In article , ethanwatethanwinerdotcom
says...


Those are not useful because they're not made of real acoustic foam.

What's the difference between mattress foam and 'real acoustic foam'?
Is the mattress foam completely useless, or just less effective? TIA.
--------------
Alex

Alex Rodriguez wrote:
In article , ethanwatethanwinerdotcom
says...


Those are not useful because they're not made of real acoustic foam.


What's the difference between mattress foam and 'real acoustic foam'?
Is the mattress foam completely useless, or just less effective? TIA.
--------------
Alex


foam consists of bubbles inside the rubber. In regular foam the
bubbles are isolated from eachother to make it nice and bouncy.
Acoustic foam is special trayed to open up and interconnect the bubles
so they diffuse and absorb the sound. So mattress foam is completely
useless for sound purposes.

Ian

On Mon, 13 Sep 2004 10:07:23 -0400, Ty Ford
wrote:

I really have big problems with that statement. Dead space is seldom linear.
Small dead space, when excited by a loud enough vocal (or any sound) can
still become quite resonant, thus imparting the telltale signs of a small
dead space. In fact, small spaces covered with acoustic foam actually sound
sort of spongy when excited enough.

Are you just saying that dead space is unachievable?

When you say voice-overs do you mean talking or singing and are we
talking male or female voice?

Primarily talking, but occasional singing may take place.

Male voice.

-F

"Laurence Payne" wrote in message
...
On Mon, 13 Sep 2004 10:07:23 -0400, Ty Ford
wrote:

I really have big problems with that statement. Dead space is seldom
linear.
Small dead space, when excited by a loud enough vocal (or any sound) can
still become quite resonant, thus imparting the telltale signs of a small
dead space. In fact, small spaces covered with acoustic foam actually
sound
sort of spongy when excited enough.

Are you just saying that dead space is unachievable?

An anechoic chamber would be rather difficult to achieve
in the average house, I'd think.

Hal Laurent
Baltimore

"Hal Laurent" wrote in message
...

An anechoic chamber would be rather difficult to achieve
in the average house, I'd think.

If a picture falls off the wall in a house and nobody's there to hear it,
does it echo?

On Mon, 13 Sep 2004 20:01:46 -0700, "Jim Carr"
wrote:

If a picture falls off the wall in a house and nobody's there to hear it,
does it echo?

Not if suitable bass traps are installed :-)

CubaseFAQ www.laurencepayne.co.uk/CubaseFAQ.htm
"Possibly the world's least impressive web site": George Perfect

Alex,

What's the difference between mattress foam and 'real acoustic foam'?

Ian has the right idea. Acoustic foam has fissures that connect all the
cavities, so sound is absorbed as it travels deeper and deeper into the
material. The sound energy is converted to heat via friction. With
non-acoustic foam all the cavities are isolated so sound hits the first
pocket and bounces right out again.

Note that foam is not a diffusor - it absorbs only.

--Ethan

Ian,

Dead space is seldom linear.
Not sure what you mean by that

What Ty means is the absorption is not the same at all frequencies. This is
a big problem with thin materials like sculpted foam. They absorb only the
upper mid and high frequencies, but do little below 500 Hz where "chesty
sounding" resonances still develop due to the short room dimensions.

Often a recording beginner will put up a bunch of foam and claps his hands,
and it sounds dead, so he assumes the space is dead. But hand claps don't
excite the lower frequencies, which are still booming. The same issue
applies to much lower frequencies. The proper approach to acoustic treatment
is absorb to as low a frequency as possible.

--Ethan

Ethan Winer wrote:
Alex,


What's the difference between mattress foam and 'real acoustic foam'?


Ian has the right idea. Acoustic foam has fissures that connect all the
cavities, so sound is absorbed as it travels deeper and deeper into the
material. The sound energy is converted to heat via friction. With
non-acoustic foam all the cavities are isolated so sound hits the first
pocket and bounces right out again.

Note that foam is not a diffusor - it absorbs only.

It's funny, I wondered about that as i wrote it. i think I was
thinking of the profiled stuff that diffuese too.

IAn

There's a lot of half truths buried in all the above information. I'm not
always right, but let me at least jump in he

- There really isn't much difference from acoustic foam and many other
kinds. The big differences a Acoustic foam is colored to look nice,
acoustic foam is made of stuff with a low flammability so it's safe to put
on walls, acoustic foam is sculpted into wedges. That's what makes it work.
When sound hits flat foam, it might absorb 40% of it (randomly chosen
number). With properly sculpted wedges or pyramids, it'll bounce off into
another part of the foam (instead of back into the room) where another 40%
is absorbed, then it's bounced deeper into the groove for another 40%, etc.
The shape is the most important part.

- The great thing about pro-quality acoustic treatments is that the
frequency response affected is a known quantity. The thicker the foam, the
lower the note it will absorb, and flat frequency response is the goal.
Putting up blankets and carpet starts working on the high end (which will
make the room sound dead) but doesn't affect the low end much, leaving a
boomy, thumpy room.

- In fact, almost all small rooms have way too much bass reverberation. In
music studios, great care and expense is focused on diffusing sound at full
frequency, to make the room sound nice. A wall of bookshelves filled with
books makes an excellent diffusor. In a small voice studio, better to make
it flat and dead; there's tons of technology that can add some sparkle or
environment to the recording later. That means you need a lot of
absorption, or bass traps, or probably both.

If you really want absorbent, and you don't want to spend any money, press
record and take your script and mic and walk into a stuffed closet. That's
about how much fabric you'll need to really make it dead, full-frequency
dead. If you have a large, walk-in closet, filled with clothes, that might
already be a surprisingly good voice booth.

You need to treat at least three of the six surfaces in a rectangular room,
to keep it from looking like parallel mirrors to the sound. My room sounds
pretty good, with rug on the floor (ceiling untreated), west and north walls
covered with drapes, east and south untreated (except for shelves of books
and LPs). However, it still needs bass control, and I plan on building some
traps of my own. As it stands, it's a textbook example of why egg crates or
a couple quilts won't do it. Even for a female voice artist, there are
upper bass nodes in a small room which will really smear a recording.

The better your room, the farther you can get from the mic. In a really
good room, you ought to be able to move from six inches to three feet from
the mic, and the main change will be the volume. If you can record, say, 18
inches from the mic, and it doesn't sound like an Amoco bathroom, and the
noise level is still below -55 or -60, you've got a pretty good room.

Goodwill sells the best and most soundproof stuff I have ever tried.
Forget those expensive acoustic foam pads and mattresses. I have
discovered recycled polyesther filled retangular sleeping bags and
bedspreads. Big King Sized ones for $5.00 each in some cases. And it
comes in colors.I just finished a walk in closet with a 1/2" (remember
its sound not R value) layer of Dow Corning Foamular 250 (about $7.00 a
sheet for 24x96) velcroed to the walls and door for the first layer.
Then overlaid with 4 layers of Goodwill acoustic padding (sleeping
bags) cut to size and pinned with 1.5" or 2" T pins from the fabric
store. I did use acoustic foam pinned to the velcroed Foamular on the
ceiling. I did it all for about $75.00. It's completely dead (i thought
I heard a knat fart the other day) in my new voiceover booth.


In article , Fleemo
wrote:

I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

Thanks.

P.S. And if you can afford it, replace the closet door with one with a
window in it.


In article , zz zzzz
wrote:

Goodwill sells the best and most soundproof stuff I have ever tried.
Forget those expensive acoustic foam pads and mattresses. I have
discovered recycled polyesther filled retangular sleeping bags and
bedspreads. Big King Sized ones for $5.00 each in some cases. And it
comes in colors.I just finished a walk in closet with a 1/2" (remember
its sound not R value) layer of Dow Corning Foamular 250 (about $7.00 a
sheet for 24x96) velcroed to the walls and door for the first layer.
Then overlaid with 4 layers of Goodwill acoustic padding (sleeping
bags) cut to size and pinned with 1.5" or 2" T pins from the fabric
store. I did use acoustic foam pinned to the velcroed Foamular on the
ceiling. I did it all for about $75.00. It's completely dead (i thought
I heard a knat fart the other day) in my new voiceover booth.


In article , Fleemo
wrote:

I'd like to create a makeshift soundbooth in my home. In one entryway,
the walls amount to a three-sided, 3 & 1/2 foot booth. At Target I
saw inexpensive foam mattress pads which I might be able to attach to
each wall. Should I seal off the fourth side of the booth, or is that
unnecessary? The ceiling is acoustical (cottage cheese). Should I add
foam up there too? Would this make a decent soundbooth?

Thanks.

Ethan Winer wrote:

Alex,


What's the difference between mattress foam and 'real acoustic foam'?


Ian has the right idea. Acoustic foam has fissures that connect all the
cavities, so sound is absorbed as it travels deeper and deeper into the
material. The sound energy is converted to heat via friction. With
non-acoustic foam all the cavities are isolated so sound hits the first
pocket and bounces right out again.

Note that foam is not a diffusor - it absorbs only.

Ethan, I think I've asked you this before but got diverted
in mid discussion so I hope you don't mind if I ask it again.

What kind of plug or sandwich would you recommend if one
wanted to, as closely as possible, terminate a tube with the
characteristic impedence of air? An active LF element
beyond the passive termination is an acceptable part of the
desired setup.


Bob
--

"Things should be described as simply as possible, but no
simpler."

A. Einstein

"Laurence Payne" wrote in message
...
On Mon, 13 Sep 2004 10:07:23 -0400, Ty Ford
wrote:

I really have big problems with that statement. Dead space is seldom
linear.
Small dead space, when excited by a loud enough vocal (or any sound) can
still become quite resonant, thus imparting the telltale signs of a small
dead space. In fact, small spaces covered with acoustic foam actually
sound
sort of spongy when excited enough.

Are you just saying that dead space is unachievable?

Ever priced an anechoic chamber that was spec'ed for below 40 Hz? I would
say that space that is truly dead at all audio frequencies is not acheivable
in any practical home studio, unless the studioist is a multi-millionaire.
:-) However, one can do pretty darn well for practical purposes with some
absorbant material and some creative thinking, especially if one is close
miking the vocalist. It isn't necessary to create a truly dead space, a
space that is fairly dead with no big peaks and dips in response at vocal
frequencies can make vocals sound very good.

"Laurence Payne" wrote in message
...
On Mon, 13 Sep 2004 20:01:46 -0700, "Jim Carr"
wrote:

If a picture falls off the wall in a house and nobody's there to hear it,
does it echo?

Not if suitable bass traps are installed :-)

Ok, if your "Billy the Singing Bass" Plaque falls off the wall, will it hit
the floor and make a noise to echo, or will it get caught by one of your
bass traps before it hits the floor? Isn't that what bass traps are for?
*ROFL*

"Bob Cain" wrote in message

Ethan Winer wrote:

Alex,


What's the difference between mattress foam and 'real acoustic
foam'?


Ian has the right idea. Acoustic foam has fissures that connect all
the cavities, so sound is absorbed as it travels deeper and deeper
into the material. The sound energy is converted to heat via
friction. With non-acoustic foam all the cavities are isolated so
sound hits the first pocket and bounces right out again.

Note that foam is not a diffusor - it absorbs only.

Ethan, I think I've asked you this before but got diverted
in mid discussion so I hope you don't mind if I ask it again.

What kind of plug or sandwich would you recommend if one
wanted to, as closely as possible, terminate a tube with the
characteristic impedence of air?

Air.

Plugs don't work on the principle of matched impedances. The trick is to
implement a mismatched impedance in such a way that you don't create too
many standing waves.

On Tue, 14 Sep 2004 11:04:26 -0400, Ethan Winer wrote
(in article ):

Ian,

Dead space is seldom linear.
Not sure what you mean by that

What Ty means is the absorption is not the same at all frequencies. This is
a big problem with thin materials like sculpted foam. They absorb only the
upper mid and high frequencies, but do little below 500 Hz where "chesty
sounding" resonances still develop due to the short room dimensions.

Often a recording beginner will put up a bunch of foam and claps his hands,
and it sounds dead, so he assumes the space is dead. But hand claps don't
excite the lower frequencies, which are still booming. The same issue
applies to much lower frequencies. The proper approach to acoustic treatment
is absorb to as low a frequency as possible.

--Ethan



Persactly!

Thank you Ethan.

Regards,

Ty Ford



-- Ty Ford's equipment reviews, audio samples, rates and other audiocentric
stuff are at www.tyford.com