carpet and room dimensions

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hello,

moving along on my iso booth here.

i have a question: let's say there is 3/8" thick carpet padding and
then 3/8" pile carpet on top of that. would you count that in the
vertical height of the room dimension?

meaning, if the room height is 80 inches, would you subtract 3/4" inch
to consider the room height as 79 1/4"?

i'm trying to figure out how tall to make the walls to get a "golden
ratio". since the top coating of the floor will be carpet/padding, i'm
wondering if it's a factor or not.

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so maybe split the difference and consider 3/8" padding + 3/8" carpet
to be 3/8" total rather than 3/4" ?

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genericaudioperson@hotmail.com wrote:
> i have a question: let's say there is 3/8" thick carpet padding and
> then 3/8" pile carpet on top of that. would you count that in the
> vertical height of the room dimension?
>
> meaning, if the room height is 80 inches, would you subtract 3/4" inch
> to consider the room height as 79 1/4"?

From an acoustic prediction point of view, the thickness of the carpet
is not significant, however, its absorption coefficients are highly
significant.

If you are planning to use porous absorption in the walls, then their
thickness is significant. A porous absorber of a given thickness will
have a measurable impedance which will, in turn, affect its absorptive
properties. However, the hard wall behind the absorber (with or without
an air gap), is considered to have an infinite impedance.

The impedance of the porous absorber layer(s) on the walls can then be
modelled using a transfer matrix, and you can then arrive at the porous
absorber's absorption coefficients.

I have written a couple of spreadsheets that will predict:
1) The basic acoustic properties of a rectilinear control room
2) The absorption coefficients of a porous absorber

You can download these free of charge from
http://www.rmmpnet.org/members/ChrisW/index.html

Please read the instructions on the download pages carefully!

> i'm trying to figure out how tall to make the walls to get a "golden
> ratio". since the top coating of the floor will be carpet/padding, i'm
> wondering if it's a factor or not.

Don't get too hook up about these "golden" ratios. Recent research by
Trevor Cox et al from the University of Salford (Manchester, UK) has
redefined the meaning of an acoustically "suitable" room. This
completely alters the perceived benefit that many of these ratios are
supposed to provide.

This is because a room's modal frequencies will vary depending on not
only the ratios, but also the absolute dimensions. Therefore, Trevor
Cox has defined the suitability of a rooms dimensions on the basis of
the degree of bass resonance (The lower the better). In the spreadsheet
"Control Room Calculator", there is a diagram on sheet "Room Ratios"
taken from Trevor Cox's website that shows this.

Bolt produced a set of ratios that were considered good (these are often
incorrectly attributed to Sepmeyer)

H:W:L 1.0 : 1.14 : 1.39
1.0 : 1.28 : 1.54
1.0 : 1.60 : 2.33

Of these, the first (1.0:1.14:1.39) is the closest to being considered
good according to Cox's new definition.

Chris W

--
The voice of ignorance speaks loud and long,
but the words of the wise are quiet and few.
--

Archived from groups: rec.audio.pro (More info?)

wow, thanks Ethan.

at the likelihood of looking really stupid:

i should count neither the carpet nor the padding in my room dimension
calculations.... pretend the floor really "starts" at the hard stuff
under the carpet padding.

do i have that correct?