3000W Chinese Gensets Info.
professor95 wrote: EDIT ADDED 45/5/2013- When this thread started in March of 2005, I never expected to see it survive this long or amass the quantity of information that has been shared here. In...
Forum Discussion
daytona7
What you are describing is a Hermholtz Acoustic Trap/Resonator. It's a very effective sound trap that is tuned to specific frequencies. There's lots of reading to be done on this concept on the web. A classic example of this is blowing across the mouth of a glass softdrink bottle. That tone it makes happens to be the freq. it will trap. Stack a grundle of those on a wall in a room and those bottle will take that freq. out of the room. Phone booths in airports (remember those?) had stainless metal with holes in it, backed by dense fiberglass isolation. Only 1" thick, they would absorb the freq. that were common in large spaces but not the voice range.
Soooo, what you need is to do a spectrum analysis of the generator IN it's environment. You're going to see a spike in a the overall spectrum. That's what you want to kill/absorb. You can't do much about low freqs. They are to long a wave to deal with in the confines of an RV. But you can mount the generator on iso-mounts and keep lots of that low freq. from transmitting to the frame of the RV, making the RV a speaker...essentially. I've long since lost my files and spread sheets on hole dia vs. hole spacing vs. depth of absorber space = target freq. range. But you can find that info./formula on the web and make a quick spread sheet to plug in numbers.
Off the top of my head... standard Peg board with 1/4" holes + 1" HVAC duct board will just about nail the bulk of the nasties put off by our generators.
It might seem counter intuitive, but put the hard side of the peg board out (facing the noise source). Use a good construction adheasive to bond the rough side of the board to the fiberglass side of the duct board. (FYI, you can buy damaged or seconds HVAC duct board cheaper. Look to your local HVAC contractor as a source.) Do not plug the holes with smooshed adhesive. IF you build it to fairly close tolerances, corners all match up squarely, you can use metalized HVAC duct tape to hold it all together. DON'T use Duct tape... it has to be the metal tape... about 4" wide.
I'm not sure heat paint will do much for you in protecting the peg board. It will make it more weather resistant which is a big plus. I would paint it with Hammerite paint. That stuff is really tuff and very weather resistant.
Just my 2 shilling worth. I use this construction method and materials all the time in acoustic sensitive room designs.... only there we cover the face of the absorber with fabric.
Oh, another cool thing about the 'sandwitch' construction... you can put it on the table saw or use a skill saw and cut a door in it. Just add 1x1" wood pieces where the hing screws in. If you can taper the door cut, the better it will work at keeping sound from escaping from the cut-out area.
What you are describing is a Hermholtz Acoustic Trap/Resonator. It's a very effective sound trap that is tuned to specific frequencies. There's lots of reading to be done on this concept on the web. A classic example of this is blowing across the mouth of a glass softdrink bottle. That tone it makes happens to be the freq. it will trap. Stack a grundle of those on a wall in a room and those bottle will take that freq. out of the room. Phone booths in airports (remember those?) had stainless metal with holes in it, backed by dense fiberglass isolation. Only 1" thick, they would absorb the freq. that were common in large spaces but not the voice range.
Soooo, what you need is to do a spectrum analysis of the generator IN it's environment. You're going to see a spike in a the overall spectrum. That's what you want to kill/absorb. You can't do much about low freqs. They are to long a wave to deal with in the confines of an RV. But you can mount the generator on iso-mounts and keep lots of that low freq. from transmitting to the frame of the RV, making the RV a speaker...essentially. I've long since lost my files and spread sheets on hole dia vs. hole spacing vs. depth of absorber space = target freq. range. But you can find that info./formula on the web and make a quick spread sheet to plug in numbers.
Off the top of my head... standard Peg board with 1/4" holes + 1" HVAC duct board will just about nail the bulk of the nasties put off by our generators.
It might seem counter intuitive, but put the hard side of the peg board out (facing the noise source). Use a good construction adheasive to bond the rough side of the board to the fiberglass side of the duct board. (FYI, you can buy damaged or seconds HVAC duct board cheaper. Look to your local HVAC contractor as a source.) Do not plug the holes with smooshed adhesive. IF you build it to fairly close tolerances, corners all match up squarely, you can use metalized HVAC duct tape to hold it all together. DON'T use Duct tape... it has to be the metal tape... about 4" wide.
I'm not sure heat paint will do much for you in protecting the peg board. It will make it more weather resistant which is a big plus. I would paint it with Hammerite paint. That stuff is really tuff and very weather resistant.
Just my 2 shilling worth. I use this construction method and materials all the time in acoustic sensitive room designs.... only there we cover the face of the absorber with fabric.
Oh, another cool thing about the 'sandwitch' construction... you can put it on the table saw or use a skill saw and cut a door in it. Just add 1x1" wood pieces where the hing screws in. If you can taper the door cut, the better it will work at keeping sound from escaping from the cut-out area.
