Non Insulating Sound Proofing

What sort of a blower? Electric, gas..? portable, stationary...? Indoor, outdoor...?

It is an electric blower slightly louder but similar to a shopvac sound. It is portable so it can be used indoor or outdoor. It is relativily small; about the size of gallon of milk.

Well drawing from my own experience most of the noise comes from the intake....You can make a baffle tube to dampen this noise....remember negative pressure air needs no aerodynamic consideration....This should be mostly high frequency noise....

I would also isolate the motor from the housing with rubber mounts, with no transfer of vibration.....then possibly using sound proof cladding to enclose the blower ... any vents could be constructed as privacy type vents that have opposing angle slats on either side....

This looks like the inside of an automotive muffler, which might help the OP.

Noise on the intake is interesting, I never experienced that... , there are a mufflers that actually acts in bouncing the sound into its self to cancel out the sound, unlike your sketch which directs the sound to sound absorbing material.

but like all mufflers, you do lose flow.

What are you asking?

Sound is mechanical vibration.

Lead is the best sound dampener there is.

Adding insulation to the blower enclosure should have no effect on cooli, unless you are blowinging air through the walls.

More detail please.

It is an electric blower with a similar motor to a shopvac hence the noise. the whole blower assembly is about the size of a gallon of milk. It is squirrel cage style and is a brushed motor. Im not looking for prolonged use just something to quiet it down

The noise comes from the blower and the air movement it causes.

Move it away from your ears by using ductwork, or use hearing protection.

If it is a brushed motor, just reduce the input voltage until it sounds the way you want. You will, of course, get less air flow. One really easy way to do that is to insert a diode (of appropriate voltage and current rating) in the line. A better way would be to use a variable transformer to determine the voltage you prefer, and go from there.

This is in addition to whatever sound absorption you install.

'Lead is the best sound dampener there is.'

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.....to paraphrase someone who is likely to read this: ¿Do you expect us to assume that you are an expert in these matters?

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Such an unspecified/unlimited claim about the superiority of Pb as a sound dampener might be an ideal place to link a reference....for those who preach the necessity of such things.

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Sure, mass generally helps with dampening vibration, but wouldn't an equal mass of magnesium dampen far more effectively than lead over most frequencies?

Extraordinary claims require extraordinary support....and some people should demand of themselves no less than they do of others.

Re: "Such an unspecified/unlimited claim about the superiority of Pb as a sound dampener might be an ideal place to link a reference...."

Me thinkx Lyn was most certainly dating himself, somewhat, with that statement... resonating "quite easily" within this old skull.

I , myself , had previously posted both HERE and (post #16) HERE references to the Klipsch Audio Papers*, some fascinating reading for any-and-all individuals who consider themselves to be true audiophiles.

[*P.W. Klipsch, the "legend-in-his-own-time" for whom NM State U's School of Electrical and Computer Engineering was renamed].

The set of papers that -I- received included a collection of Klipsch's "Dope From Hope" periodicals. In paragraph 3 of this Road Tips blog, the link to those papers is now dead; BUT, if you act quickly enough (as of today) THIS link still delivers the "Dope From Hope" collection.

THEN, if you scroll to page 23-of-71 in that pdf (_{DOPE_from_HOPE}), you will see PWK's reference to the use of Acousti-Lead, a pliable/formable thin sheet of lead that nowadays, the EPA/OSHA and a dozen other "control-freak-agencies" would H_A_N_G anybody for using...!

In "Pound-of-performance-per-dollar", it would be hard to beat ["mini-kudos, Lyn"]~

However ... "time moves on", and now (another "legend-in-his-own-time") Peter D'Antonio [B.S. from St. John's / Ph.D. from the Polytechnic Institute, Brooklyn; 29 years of research in diffraction physics at the Naval Research Lab, and member of the internationally renowned Laboratory for the Structure of Matter], having established the current standard for the modern recording studio, now specializes in more aesthetic (and healthy) approaches to "sound control".

[[ er ... you wanted links , yes...]]

GA. Thanks for the Links!

I was able to download the Dope from your THIS link. I was more than trivially interested, Having purchased a pair of Klipsch speakers just this last Christmas.

I've only read a few paragraphs, but it certainly appears to be worth reading/studying.

Very much appreciated.

You might start by replacing any worn bearings, checking any vibration mounts, and tightening up all fasteners.

https://www.google.com.au/search?q=egg+crate+sound+insulation+images&ie=utf-8&oe=utf-8&client=firefox-b-ab&gfe_rd=cr&ei=5aCdV9CBO8_v8AfWv4PQBQ Cheap!

First make sure the blower is isolated from the floor or walls with vibration-absorbing pads or grommets. Any attempt to deaden the sound of the air will be useless if the blower is coupling its vibration into the walls or floor, making them carry the sound as well.

Then do a google search for acoustic insulating foam. (I know amazon.com sells it.)

Check out "Quiet Rock", or a knock off--It is regular Drywall that has a layer or more of sheet Aluminum embedded. Comes with isolation caulk etc. Heavy, but easy to use and kills off a lot of frequencies. As imagined, multiple layers, with staggered framing improves the package. Let us know what works.

First of all a shop vac style blower is an axial fan not a squirrel cage.

Second, I would recommend you source any type of Squirrel cage fan/blower and use it as you spot cooler. I Drag one or two of these everywhere I go to cool off as well as to exhaust dirty air etc. I even made a box to draw air through 14x20 filters that holds one of these fans.

I replace them after I beat the hell out of them with a smile on my face because they are the best for the money that I know of. They make for a handy extension cord too.

However. If you want the most portable and cost effective way to deaden that noise... blow up balloons. Make a shroud out of connected balloons. I'm only saying so because I've done so. (I used to be a professional balloon "engineer") It's also the most festive way to conceal a generator.

Try this simple test. Place an inflated balloon between your ear and something really noisy. The balloon will vibrate and absorb a lot of frequencies.. You heard it here first and yes I had that job.

A dog works really well too....

Who's a sound deadening living art sculpture?

Hey he's really good, I can't hear a thing....

Here's a picture of a balloon engineer.

No no.. Not that type.

this type..

lots of corporate events and such.

Make sure it's well anchored. Or say hi to the 'Wizard of Oz' for me.

"Here's a picture of a balloon engineer.

"

"No no.. Not that type.

this type..

lots of corporate events and such."

Nothing says the two are mutually exclusive. Although that truck *IS* impressive, is it all balloons, or is there a rigid supporting frame underneath the latex?

You should really state your problem more completely, but generally speaking, carpet and carpet padding scraps hung in multiple layers around any loud device(generators, blowers, crying babies, etc.) make a good acoustic baffle.

What happens when you switch the blower off?

Yeah, I was going to say the same thing, just turn it off, and it's dead silence.

Lead is a still a great noisy deadener! Especially when projected out the muzzle of a shotgun!

A larger blower operating at a slower speed will reduce noise.

A great comment.

I do have to say, it appears the holes in successive boxes are closer to 180 degrees out than 90.

Well spotted sir! Top marks. I did realize that when i started to try and explain the obvious, it was going to be tedious, so I leave it up to discerning folk like you to tidy up the details. It does work though, and I was pleasantly surprised to find it worked better that I thought it would without modification. Still does after many years. Each layer takes about 26 db from the source, so 1 or 2 layers not really enough.

I like it, but might have to derate the cfm in this configuration...A larger blower(as someone suggested) might mitigate the noise further....

three hours of labor and material for a $1 motor that would fry if it were left on.

Please don't burn the mdf!

Great!

Actually a $500 + German motor from 1956, which runs all day without the slightest hint of overheating because its body is entirely cooled in the airflow it provides. Look at the plans.

I was speaking of the OP. I like your design.

I imagine a blower I might salvage from a vac or pick up at American Science ans surplus.

like this

You used MDF deliberately as it is heavy ( dense ) board. In my youth we built speaker boxes using the cheapest chip board as it was thought that the thick, less dense board was a better sound deadener. Is this not the case? Jim

No I think the denser the material the better the sound deadening characteristics....I know they sell thick plastic sheet for just this purpose...

Mass does generally correlate with better dampening....not sure density in and of itself does.

Magnesium is generally great at dampening sound/vibration, especially when compared on a per mass basis.

Adding_TO the above --- there are certainly a LOT more factors (as has already been pointed out) that come into play, insofar as reducing "noise".

The problem is ubiquitous. I have a rather worn-out book (first edition, from my father's collection) titled "The Effects of Noise on Man", which harkens back to studies done long ago, such as the perpetual clattering of sewing machinery in early London apparel factories, and its effect on many of the workers therein.

The solutions to the multitudinous noise-problems man has created are numerous indeed. And, too, many tables exist (think OSHA, etc) dictating what is "tolerable" and what is not.

Interestingly, what is PERCEIVED to be a problem is not always, necessarily, a problem.

In the "beginning", designing the first Sea Wolf (sub), there was a serious cry that the ventilation noise within the communications room was "too loud". Measurements were 'above-and-beyond' specification.

As it turned out, nothing needed to be done at all; the spec had been incorrectly written...!

In the case of the "blower noise" : perhaps the problem is that you aren't working or standing far enough away from it (), or, maybe you need a different type of music playing "in-harmony" with it...<wink>

I *do* hope you find happiness with the situation.... without having to invest in too many exotic / expensive materials, or spending too much time at it....

If acoustic impedance correlates to electrical impedance, as I presume/suspect, then there will be a frequency dependence. I didn't see any reference to frequency.

Also, I'm accustomed to working with (electrical) impedance due to discrete devices, and have no experience with the impedance inside a single device/object. What is the relationship between impedance and attenuation over ≈10 octaves?

You are absolutely correct --- and I'm pretty sure that at least one of the *links* that I provided delves into that relationship.

There are very few instances where I, myself, have had to work with the formulae that incorporate (carbon steel/zinc/aluminum/water) "Z" factors... but it is one of those subjects, about which, "familiarity" is mandated, here.

I have doubts about being able to see even general trends for damping looking at acoustic impedance alone.

Check out the Z values for iron, steel, brass and copper as compared to lead. They all show higher impedance than lead, yet no one has come forth with stories of sound proofing with steel merely because it is cheap and has a high Z.

I suspect that much like the electrical analog a large impedance mismatch may lead to significant reflection, but doesn't indicate much about absorption.

Perhaps, if the electrical analogy remains useful a little deeper, knowing more about the reactive vs. resistive components of impedance for specific materials would provide insight into effectiveness at sound absorption.

"I have doubts about being able to see even general trends for damping looking at acoustic impedance alone."

So do I <wink>... {{ That's why I did the "Adding_TO" post (49) immediately-below the contribution of 48...}}

You are "spot-on" regarding "significant reflection"... (the quotient of the differences between 2 materials' Z's, divided by their sums yields the "Reflected Pressure", while squaring both the dividend and the divisor yields the "Reflected Energy")

In addition to "Acoustic Impedance", there is that ol' "Attenuation Factor" with which to deal.

If you are ever afforded the opportunity to hold (alternately) a 3-inch cube of carbon steel and a similar cube of lead snugly against your ear, and tap lightly with a hammer... DON'T DO IT...(!)

While you might survive the "thud" from the lead, words alone cannot describe the *shriek* that will explode from the depths of your lungs, when that "tap" on the steel drills a veritable hole through your skull.

Noise reduction is a science unto itself... much akin-to the study of corrosion control.

The less you know, the less important things seem (and thus, the less "complicated" they seem).

And ... In the immortal words of one of the greatest poets of all (Henry Wadsworth Longfellow)

"things are not what they seem"

Its all about the integrity of the board and in this case the ability to easily fabricate airtight chambers. Its true chipboard would also do the job. Here MDF is cheaper.

Also the separated masses work well together, as the vibrations dont travel well through the widely differing media.

Is the size of the separation important? Would the final composition be improved if the spaces were different widths to prevent the second wall finding harmony with the first at a specific frequency? Jim

Good thinking but yes and no because each wall is a different size

I should have added that the boxes are not cubes, typically ratios of 1 :1.26 :etc

They are de-coupled by the air vents from low-f and decoupled from mid hi-f by size differences. So when you have two parallel resonant surfaces, making holes in ONE of them decreases the STC.

That's plainly not intuitive but then - think of two drum skins. Then make holes in one of them . . And if you are thinking of parallel resonance, the frequency is way up there, 12K with a 25mm air gap. Such HF doesn't hang about for long.

And again you are right as well : in reality it is quite hard to get the boxes to stay precisely aligned because of the springs, which is a GOOD thing, as the gap is randomized. The stuffing in between stops them swinging into direct contact which would be a BAD thing. Interesting topic. Its a serendipitous idea as it has at least three unexpected advantages. When I hit three i usually stop and dont worry any more!

The sound deadening drywall is better.

.used both in sound studio construction.. sheet lead , layered , is the best

GA.

I'm going to have to add a few more terabytes of storage, just for all the links I get from CR4!

I think I brought this up here at CR4. is to have a section of handy links.

that's broken down into

• Programs
• data
• information

it'll be like a engineering depository

Or maybe I just dreamed it...

Excellent idea. I didn't see it previously...

To be really useful, each link should have a fairly extensive set of keywords, so different people thinking from different points of view can still find them. Perhaps an inverted "tree" search to start with relatively general concept, then narrow it down bit by bit...

yes, were thinking alike and broken down so it can be drill down to specifics.... as to the sections here, chemical and mat'l science, manufacturing, software and mechanical and then drill down farther to more specifics

like mechanical

HVAC, Utility, Power, Stress

There may be cross over. but just a thought.

I recall a number of links I know was on CR4, but I can find them. One specifically, was a link for an excel sheet for lifting lugs, from I believe compress (ASME software). it was a little off topic. I spent hours looking for it, but couldn't find it.

I think I brought it up when CR4 was asking for suggestions...

Yep, I brought it up as well: http://cr4.globalspec.com/thread/83526/The-Ideal-Site-for-Engineers

A library would be a very handy tool.