Sound Proofing
Sound Proofing
(OP)
My 10-year-old granddaughter had a school project to build a containment that will completely block the sound from an I-phone (V5). Her father said to take in a bucket full of water, drop the phone in and it won't be heard. I thought that there must be a less destructive way to do it.
The sound from the closest thing we had to an I-phone (Galaxy S3) was 75 dba (with a background of 30 dba). The steps I took were
I don't have instrumentation to evaluate sound frequency, just magnitude. I could not determine a specific part of the box that was leaking (the 5 dba over ambient was consistent wherever I held the meter (always about 6-inches from the box). Anyone have any ideas?
The sound from the closest thing we had to an I-phone (Galaxy S3) was 75 dba (with a background of 30 dba). The steps I took were
- Build a small box out of 3/4 inch particle board. Top and bottom were two layers (1.5 inch) thick (second layer fit inside the sides). Sides were 3/4 inch thick. Inside of the box was 8" X 8" X 3". That cut the sound to 68 dba
- Put high density foam pad on bottom and sides of box. Sound 65 dba.
- Got a 16" X 24" X 8" plastic box and put high density foam mat in the bottom. Then a layer of minimally expanding spray foam, then the wooden box, finally filled the plastic box with spray foam. Sound 55 dba with the lid off.
- Put a 10" X 10" high density foam mat on top of the wooden box then another mat over the inside of the plastic box and put the lid on. Sound 44 dba.
- Put 2-1/2 inches of minimally expanding spray foam on top of the plastic box lid. Sound 35 dba.
I don't have instrumentation to evaluate sound frequency, just magnitude. I could not determine a specific part of the box that was leaking (the 5 dba over ambient was consistent wherever I held the meter (always about 6-inches from the box). Anyone have any ideas?
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist





RE: Sound Proofing
Maui
RE: Sound Proofing
RE: Sound Proofing
Good luck.
RE: Sound Proofing
Weight is an issue, she has to be able to carry it on the bus to school. Size is also an issue, it can't be bigger than 30 inches in any dimension (so size pushes a vacuum chamber out of consideration.
I've always relied on changes in material to filter different frequencies, but it isn't working to get the last 5 dba here.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
http://en.wikipedia.org/wiki/Vacuum_flask
How much money do you want to spend Zdas? We use the opposite of what you're describing with our precision instruments - i.e. we put them in enclosures to keep sound out.
We've had some success with alternating layers of dampers and absorbers plus mass loaded vinyl or similar. However, we're concerned not just with audible noise but lower frequency vibration too.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sound Proofing
Or if you want to bend the rules, is the sound coming from the ringer? Completely shielded box, no reception, no ring, no sound.
RE: Sound Proofing
RE: Sound Proofing
Maui
RE: Sound Proofing
A.
RE: Sound Proofing
My wife and granddaughter are on the way to the store with my son's i-phone to buy a thermos. I can't believe I wasted $100 and 20 hours work if this works (it wasn't a waste I spent the time with my granddaughter and that was fun).
I'll let you know how that works.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
RE: Sound Proofing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
The commercial product usually comprises a ~1/8" thick sheet of PVC-ish plastic that is apparently compounded with lead dust or something similarly dense, bonded to 3/4" or more of polyurethane foam on both sides. It can be cut with a circular saw and bonded with contact cement. Soundown is one source. They don't usually give it away.
Foam/plywood/foam may work.
Foam/metal/foam may work better.
It isn't necessary that the mass layer be completely contiguous. A cardboard box, covered with a layer of flexible foam, with flat metal plates bonded to the faces, and with more flexible foam covering all, should work fairly well.
The self-expanding canned foam is probably too rigid when it sets up. Weatherstrip type foam is about right.
Mike Halloran
Pembroke Pines, FL, USA
RE: Sound Proofing
We were looking for a vacuum bottle, but everything in this town had a bottle mouth that the phone (or an ice cube) would not fit through. I still want to try that. We put the phone in a FoodSaver jar (used paper towels to keep the phone off the walls) and sucked the most vacuum our FoodSaver could do (probably 15 inHg. Sound went from 79 dba to 65 dba.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
RE: Sound Proofing
Mass is the best sound attenuator, not many applications where mass may increased without practical limits, but this project sounds like one of them.
Good Luck
www.SlideRuleEra.net
www.VacuumTubeEra.net
RE: Sound Proofing
1) leakproof enclosure
2) physical isolation of vibration source from external enclosure
3) some acoustic damping in the cavity (ie foam or rockwool
4) suppress any thin panel resonances with bitumen sheet or equivalent
5) increase surface density (kg m-2) of enclosure
6) frequency analysis
But frankly if you've pulled >30 dBA out then you might as well jump to (6)
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Sound Proofing
All of the sound work I've ever done has been to get big, low frequency point sources down to around 20 dba above ambient at 100 m. I never thought about exactly how difficult it is to get to zero dba at enclosure contact. That last 5 dba turns out to be a real challenge.
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
But showing that, with good engineering, you can meet a spec completely is a valuable lesson too.
So many teaching opportunities, so little time.......
Hope your grandaughter has had a good time with all this.
A.
RE: Sound Proofing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
Jay Maechtlen
http://www.laserpubs.com/techcomm
RE: Sound Proofing
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
RE: Sound Proofing
Food sealer bag/vac storage bag was much more practical than my thermos solution, nice one 1 gibson & Zdas.
As Gregs list points out, still need to isolate direct mechanical transference for the vacuum to work. Again working the other way round but one vibration isolation approach we used to do was put a small microscope on a big block on 'concrete' then suspend that from some long bungee chord. Replicate this inside a good partial vacuum and I'd be interested to see how it works.
(Greg, I may have to print off your list and post to my cube. Sound & Vibration is one area I feel grossly deficient in given what I work on. Then again it's not clear some of our acoustic enclosure vendors are much better.)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sound Proofing
For compressors we've found that mass and layers with changes in material are the key to getting to the sound down. In this project I've found that there is an enormous difference between "down" and "gone".
David Simpson, PE
MuleShoe Engineering
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist
RE: Sound Proofing
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Sound Proofing
RE: Sound Proofing
RE: Sound Proofing
Certainly throwing a particularly obnoxious phone someone kept leaving on their desk in a metal munition box didn't work back a few years ago.
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Sound Proofing
non-destructive, aside from a little pressure on buttons.
Jay Maechtlen
http://www.laserpubs.com/techcomm