JA> Hello Terry,  Almost total soundproofing to me is finding someplace 
 JA> neither my wife can find me, nor anyone else who wants 
 JA> me to do something on my officially proclaimed "GOOF OFF DAYS".
"Space isolation" is a perfect example of that.  Let's say, skiing, fishing, 
hunting, walking the dog on a long hiking trail, etc. depending on your 
preferences and local conditions.  "Masking audio" could be useful too.  If 
you can talk a kid into mowing the lawn, with windows open, that greatly 
reduces the attenuation needs for your other activities to not be heard.  
(Bonnie will appreciate that humor more than others here, I'll guess, as 
she's likely the one here who most uses those professional audio terms to 
clients.)  
 JA>         No, I didn't mean "total sound proofing", or for that matter, 
There's no such thing, just as the idea of a "shatterproof" eyeglass lens is 
a misnomer.  
 JA> anything near that. I did mean to pass on a material 
 JA> that is available for about the same thing you would 
 JA> pay for the same surface area and batt insulation for 
 JA> a 2x6 exterior wall, yet is extraordinarily quiet. A 
You could build that 2x6 wall with 2x4's on 12" alternate centers, with 
slightly better thermal insulation than with 2x6's through, no holes in studs 
needed for wiring, and eliminate the tympanic effect of normal studs.  Few 
add on materials you can buy offer the low frequency isolation that isolated, 
sealed layers do.  Mass in that wall helps though, with heavy commercial fire 
rated sheet rock better than common unrated types.  Of course, a poured 
concrete outer layer and an isolated internal wall is nicer.    
 JA> good example is the D-9 Cat tractor operating about 50 
 JA> to 75 feet outside the structure and not being heard. 
It's easy to isolate the higher frequencies.  The low end that rumbles the 
ground several hundred feet away takes some serious work beyond the scope of 
what you appear to be considering.  At least our hearing is less sensitive to 
low end noise.  
 JA> While not soundproof, it is a lot more quiet than 
 JA> anything used in home construction out here in this 
 JA> part of the country. No,.....the remark was intended 
The things you can do cheaply if planned during building construction are 
isolated layers, such as the 2x4's in 2x6 outer walls above, or 2x3's on 2x4 
plates inside if you want to avoid thicker walls (also with insulation, even 
if for acoustic rather than thermal reasons), and to seal up leaks.  That 
means caulking sheet rock to floor decks, avoiding windows, air ducts, or 
recessed outlets in critical isolation walls, and weatherstripping solid core 
doors even for interior rooms you want isolated.  Good acoustic isolation 
windows and doors can be made or bought, but they run up costs fast.  
 JA> what we can about our listening/living areas and get 
 JA> the best bang (or least) for the buck, in a subject so 
 JA> complex as acoustics. I swear the more I read about 
 JA> it, the less I understand and the more contradictions I find!
Isolating areas always uses the same sets of simple principles, with surface 
treatments for high end, and space, mass, and isolation (uncoupled surfaces, 
no leaks) for low end.  Defining and producing acoustically pleasing spaces 
gets more complicated, with no single ideal, and different considerations 
based on area size and shape.  
 JA>         The sandwiched material I spoke of can be used 
 JA> as new construction or in building your "building 
 JA> within a building" without extraordinary expense. I am 
One of the simplest add on patches for limited space low end isoaltion is a 
set of steel furring channels with a layer of 5/8" FC rock.  For mid/high 
treatment, find a ceiling tile distributor who'll give you an Armstrong 
architectural acoustics catalog.  They make good wall treatments ($5-10/sq. 
ft., as they have to handle abrasion plus look pretty), and much cheaper 
ceiling materials (damaged if touched).  Note the midrange noninearities of 
thin (1/2") materials, while how 1.5" materials perform much better into the 
upper bass region, much less distorting vocal frequency acoustics.  A drop 
ceiling below a sheet rock ceiling should cost about $2/sq. ft. using decent 
materials.  (If you find some spec's on so called economy "acoustic" ceiling 
tiles, you'll note they are only 35% efficient over much of the voice range, 
while good materials are 96-99%+ efficient absorbers.)  
 JA>         Q>  I read somewhere that a perfectly quiet room would not be 
 JA> the best environment as a listening area. I would be 
You don't mean "perfectly quiet".  You mean acoustically dead.  A perfectly 
quiet area is ideal, as you can add sports crowd noise, insect, urban street, 
or other noises, but you can't take them away on command if not isolated out. 
 
Live and dead surfaces, and their placement, is a subject where you could 
want several different ideal rooms for various purposes.  A jazz studio 
ideally may be much liver than a concert hall.  A vocal studio may ideally be 
live front and dead rear.  Many recording studios prefer a similar LEDE 
concept.  
In a small room it's very difficult to control acoustic modes, and so my 
preference is to generally err on the dead side for as many surfaces as is 
practical, as loads of common bare sheet rock creates uncontrollable standing 
waves.  Thin fabric coverings (drapes, quilts, acoustic fabric) I dislike 
unless backed with something like 1" or 1.5" mineral wool board, as they 
absorb sibilance but not midrange equally.  You can electronically simulate a 
larger room or more reflective surfaces, but you can't undo problem 
reflections very easily.  
In larger rooms you can calculate resonances and reflection times, and work 
with resonator units and reflector or damping panels to control the area.  
Resonators to create uniformly reflective surfaces without single frequency 
quirks (high Q points) take space and are more costly than damping materials. 
 
The LEDE concept would place your primary speakers on a live wall, which may 
resonate low end somewhat, and use a dead (absorbtive) rear wall, which would 
prevent comb filter effects from strong first order reflections.  
A common measurement of room "liveliness" is the T-60 measurement, to 
quantify how quickly a signal decays or how long it bounces around first.  
Between cost of RTA test equipment, complexity of understanding relevent 
factors, and difficulty doing much with small rooms, such analysis is usually 
only done on larger studios and more often on performance auditoriums.  
That's a subject you might study to sort out some of the confusion you've 
apparently noted.  
 JA> very interested in your thoughts on that. Also, and 
 JA> and all ideas about "sound conditioning on the cheap" 
 JA> would be greatly appreciated. I cannot tell you what a 
 JA> formidable task it seems to a novice.
You need to separate the concepts of isolating an area from those of making 
it sound pleasant as the first step.  High frequency isolation and surface 
(reflection) treatment can be one and the same material retrofits, while low 
end isolation requires building design considerations, and low end room 
moding is a mix of design and a completely different set of physically more 
awkward tools, if you bother to pursue them.  
Some small room shapes (living/rec room size) can start with strange modes 
where at some frequencies you might actually think a tone from a right 
channel is coming from a left speaker.  Other times you get luckier without 
much work.  
Terry
--- Maximus 2.01wb
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