Acoustic dampening

[reedman]

Anyone out there well versed in noise dampening? Acoustic dampening?

I like my tank to be extremely quiet and although (by most visitors comments) my tank is quiet, I always strive to quiet it down more.

My major sources of noise are the pumps: one AM3K, one mag 9.5, and one mag 7. I have shut down both of the mags to check noise levels and it seems the AM3K is making the biggest racket. So here's the thing. It is not resonating through the stand (foam underneath the pump to isolate it), but the noise is bouncing off the walls (tank is in the corner) and pushing back into the living room.

Any ideas on materials that would help to isolate the sound from the living room? I've looked at Dynomat, as I have used this with great success in cars before, but I really don't want to "stick" anything to the painted wall.

Throw out the ideas people...Thanks!

 

[jlehigh]

I cant go into the whole long acoustics speal due to a mtg I have to run to BUT I will say this. Finding your primary deflection points on the wall and treating those will help quite a bit. You could use something like dynomat but there are plenty of DIY type solutions involving high-rated insulation and some burlap. The issue there though is unless the acoustic panels are a few inches from the wall you only get about 30% of their dampening capability.

It's a tight space so your deflection points will be easy enough to find otherwise its common practice to just use a mirror. You run the mirror along the wall until you and see your sound source. That is your first deflection point. I think treating the first two feet of your wall and the back of your cabinet will go a long way assuming it is a sound deflection issue.

 

[Scooterman]

lol I was goin gto say Dynomat but then you crossed that idea out, I was thinking of lining my stand with somethng like that in the upper regions but not in th elower sections that get wet.

 

[liveforphysics]

For things with a sustained frequency that rarely shifts, I could make you setup to actively cancel the sound. It would cost at least $40 in parts though, but I could design and build it in a day or so if you are interested.

 

[jlehigh]

For things with a sustained frequency that rarely shifts, I could make you setup to actively cancel the sound. It would cost at least $40 in parts though, but I could design and build it in a day or so if you are interested.

Tell us more Luke! I will be building panels pretty soon for my home theatre and would love to see your design.

 

[reedman]

Yes, please do expand...My only concern with active noise canceling is that my home theater is in the same room and I don't want to lose any of that audio.

But please expand a bit.

 

[Krish]

Dynamat is cool...We sell the extreme here at our shop for $225 per box which consistes of 9 sheets 3ft by 1 ft. Works great in cars, but never tried it in a home. It mostly cuts down on resonance and does cancel out road noise in cars, makes things more sturdy and rigid, and will increase your SPL quite a bit. We have a customer that I used 5 boxes on his Rodeo and the difference was a 2 db increase in SPL! But in any event, you can hardly hear any outside road noise like you use to and does work wonders in cars. I may need to try out a few sheets in my stand just to see what it does...

 

[dnjan]

dynomat mailorder

Anyone got a good link to mailorder dynomat?

 

[liveforphysics]

Well, if you are concerned about looseing audio or voice conversations, things that have constantly changeing Q dont get canceled. Its really pretty simple, you just find the offending freq on an osilicope useing a full range microphone for the input signal. Often there will be 2-3 differnt frequencys in a noise that stand out, sometimes all harmonics of eachother, sometimes random. Anyways, you then take some el-cheapo source for microphones, i like to break the ear pieces off a $1.99 pair of head phones and use them for microphones. So, you play a tone through the mircophone/speakers with a tone generator while monitering the output signal (useing a "ballenced"(dont get me started) mic) on a different channel of the scope. When you find the biggest returned amplitued, you know you found your resonate Q for the headphone speakers, once you know it, you look at what freqs you wana cancel and add weight (drops of epoxy, superglue, whatever) to the diaphram until you get as close as possible to the offending freqs. So, now you have a few microphones that are super senstive to detecting the main freq components of the noise that bothers you. So, you just play that signal inverted 180deg (out of phase, aka, cancelation wave) into little op-amps, and make a phase shift circut on the input signal. Play the output of each amp into a cheapo speaker that is well suited to playing the frequency you wana cancel. You could do it all with one little speaker, but it wouldnt work as nicely. Anyways, so you stick this little deal, perhaps half the size of a shoebox or so, as close as possible to the things generateing the offending sounds. Doesnt have to be really close becuase you have phase shifting control, but it does help. Anyways, make sure the speaker and mic are faceing the offending sound source(s), and listen. It shouldnt be doing much anything but makeing more noise at this point. So, this is where the phase shift knobs come in, listen, and adjust the knob, its basically compensateing for distance, along with the delay in the amp signal proc, etc. Anyways, you turn that knob and POOF, all of a sudden that part of the sound CHANGES, not dissapears, but distinctly changes. This is when you know you are dead nuts on being out of phase. So, now you simply adjust the gain signal with a little pot or whatever inline with the mic until the amplitudes are matching, and POOF, now that part of the sound is GONE! Its cool to hear(or rather, not hear) it working for the first time, it seems like magic. Anyways, you do the same deal with the other channels to stop the remaining offending freqs, and its done. It would likely draw <5watts, and not need any maintence or dorking with after initial setup (unless the sounds its trying to cancel change).

Anyways, with the mics tuned to resonate at the Qs you are looking to cancel, its not going to cancel talking or music at other freqs hardly at all, but if you want it to be perfect, I could build in a narrow high slope crossover pretty easily inline with the signal to block out other noise from entering the amp, but it really wouldnt be needed.


If any of you guys are into high end audio, we should talk. I used to build custom super high end tube amps and normal amps in highschool for a little cash to experiment with. I have also built my own speakers, but they were for the totally retarded purpose of achieving max SPL in car... Man, the stupid things you do for money as a kid...

But yeah, I'm about 9/10th of an EE, and the 1/10th I'm missing is the digital programing BS that I hated, and isnt a part of proper audio, so if you want help picking equip and seeing through the 95% BS audio market, let me know.

 

[liveforphysics]

You guys should remember, dynomat works in cars because just like Krish said, it lowers the resonate freq of the vibrateing surface. This means dynomat is killer for sheet metal pannels and things that make annoying noises when shaken hard, sheet rock is generally a pretty quiet fellow when shaken hard. However, you will also notice that he said it increased the SPL in the car, which is very true, dynomat reflects sound really well. I'm not sure you would like the results of sticking it over your walls, however it might help to wrap your pumps in it, assumeing they dont have thermal issues.

Dynomat is asphault tar saturated tar-paper with thick aluminum foil on the back side (the foil degrades the functionality, but keeps carpets from soaking through with tar and makeing messes. There are some similarly overpriced tar and silicone sprays like V-block and other stuff you can use.

If you are looking to stop sound from reflecting off a wall, go to baskin-robbins ice cream shop, and ask them for the foam sheets that the icecream cones are packaged in. They generally always have about 6 on hand, and they just toss them in the garbage, so I've never had a problem geting them to give them away. Anyways, they are about 2ftx3ft rectangles of an open cell urathane foam with a nearly perfect surface shape for reflecting sound waves back into the foam (think high end acustic dampening foam pannels?).

I think that dingy yellow foam, generally complete with a few icecream cone crumbs would be your best shot at stoping the reflection. Now, personally I'm betting stopping the reflection wont make much of a difference, but hey, without seeing stuff in person I can just make blind guesses as to the layout.

 

[reedman]

Luke,

Thanks....sounds very interesting and might just do the trick for me. I'm going to have to think on that and check the tank for the tones coming out to see if it is one primary tone or multiple. Great info!!!

 

[reedman]

Assuming it isn't a reflection issue are there any other ways to mitigate the "noise" resulting from running big pumps? Is noise cancelation the only option or are there other choices to deaden the rooms ambient noise?

Thanks to everyone who has posted...I am learning a bunch

Man you leave the car stereo industry for 15 years and this is what happens...dynomat was the only game in town when I was trying to degrade my hearing.

 

[liveforphysics]

Reed, dont forget that with all those magnetic fields whirring about down there, you might need to sheild the mic's voicecoil from acting like an antena and trying to confuse you with electrical inductance noise appearing as sound noise. If you dont have a shielded full range mic to use, remember that you can make your own faraday cage with any old wire mesh wrapped around the mic to sheild it. Most all hand held vocal type mics do have sheilding allready though.

 

[liveforphysics]

There is always an infinate number of possible solutions to any problem, however, active sound cancelation is so cheap, easy, and not a visual eye-sore that its hard to beat.

I hear you about the car audio thing, I dont know if open headers on my racecar or the 10K+watt stereo complete with 2 high output alternators and 6 deepcycle batteries I had in my car in highschool casued it, but something has done some permante hearing damage to me. Every couple years when I get my physical and they check my hearing.... it becomes worse and worse in the high frequency range. I love to appreciate a real 2 channel hi-fi setup now and then, and I hope the hearing doesnt screw with the enjoyment i get.

 

[Krish]

If any of you guys are into high end audio, we should talk. I used to build custom super high end tube amps and normal amps in highschool for a little cash to experiment with. I have also built my own speakers, but they were for the totally retarded purpose of achieving max SPL in car... Man, the stupid things you do for money as a kid...

Sounds good...We are the Authorized dealer for Directed Electronics in the Bahamas which means we carry everything from Orion, Precision Power, Ads, Viper, Rattler, Clifford, Avital etc. We have a truck we are working on that currenty has (8) 12 inch Orions subs and (2) 2500d amps (2500 watts rms 5000 max each) running it. We are waiting on the alternator to come in that will idle at 230 amps. We are running a 20 farad capacitor on it just to keep the amps running for half volume, but at 10 volts the amps shut out so we are only hitting 154 db on our Audio Control meter. When all is finished and I am happy with things, I will post photos of it because we have some molds to make for it

Sorry for the hijack Reed...That is my field

 

[reedman]

Krish, No worries...always enjoy hearing about overkilled stereos that can out dB a rock concert....all good!

Luke, open headers are great...nothing like a little flame throwing and that great sound you can't get any other way.

So long as we are talking about high quality sound and not just dB. nothing worse than a distorted stereo thundering down the road without any high end sound coming out....Hate that!

 

[liveforphysics]

When I was in the game, DEI just released 1100d's and if you didnt mind the laggy phaseing and chopping wave of a D class( I dont think any SPL'ers ever gave a damn), they were the cats meow.

I used 2 1987 Robert Zeff designed HiFonics Colosus amps (revision B's) for subs, and 2 zapco 600CL amps (no, i didnt sucker into the symba-link thing) for my mids. That worked out to be a 600CL per speaker for mids . If I could re-do it all, I would have gutted the interior, ripped out the dash, stereo, seats, door pannels/door braceing, PS, AC, sunroof, etc and focused my energy on the engine . But, with the judgement level I had in highschool, I would likely wouldnt have survived. Car audio was at least a very safe hobby, excludeing hearing damage.

I would love to see some pics of your work Krish, I will dig up some pics of some stuff I did.

 

[Krish]

Sounds good! I wish I could get more into custom installs but the car dealers have me tied up and we turn over approxiimately 120-150 cars a month for them alone. They bring them in without any players etc, and we supply them as well as alarms and install them. That's where all the money is so when I get my guys to the point where I can trust them with the dealers, then I'll get more into it custom installs. Quite possibly, Look out for something "RF" on one of our demo vehicles This one we are doing now is just a trial thing, but the real thing will be cool... Look up the Orion H2 subs

OK...Lets get Reed a quiet tank

 

[liveforphysics]

The passenger airbag was removed and a 9" LCD display is flushed into it to use with the playstation that is flushed in the center console. But I cant find a pic of the screan. I told the clowns I could remote mount the carosel for the PS2 into some place inconspicous, and the processor for the PS2 could be hidden up in the dash, but they didnt like that idea because appearently they wanted it obvous that it had a PS2 in the dash...

I cant take credit for the whole install, a guy named Barry from portland did a lot of the pod work, and did a good deal of the bondo sanding. The head liner was also farmed out to a local upholstery shop, after I just could NOT get that fabric to look natural on there. Upholstery is really a skill all to itself. Its all my wireing design, and equipment choice though.

You might think, why would anybody put such lame shiney speaker grills over such nice speakers (grills ruin SQ), well, John the owner picked up this dumb ***** who stuck the toe of her stupid shoe right through the cone of the speaker on the SECOND day of it being finished...

 

[Krish]

Very nice! I'll see if I can get the Rodeo around to get photos of the doors I did. It houses(2) Kicker 8's as well as a 6.5 Boston acoustic mid. Pretty neat! K...Sorry Reed again. It was Luke