FWIW: 3db is equal to a doubling of sound pressure. It is not a linear scale.
Quote from: FuzzyGrub on October 07, 2019, 03:37:45 PMFWIW: 3db is equal to a doubling of sound pressure. It is not a linear scale. What did you use to measure the db?
FuzzyThanks for all the great work you did. Always quite a subjective subject. Everyones ear is a little different (frequency response and amplitude etc). The best information I have ever read about moderators, was a post in AGN, by Sto who designed powder burner moderators for the industry. In a multi page comparison of airgun moderators titled "Moderator Design,Testing & Evaluation, he tests almost all of the commercially available moderators for air guns. Long, difficult to read and somewhat difficult to interpret, my take away was LEGNTH HELPS. If I'm reading your conclusion right, it's simmilar? Distance past the barrel improves sound attenuation. Therefore moderators become a compromise of legnth, diameter, weight, looks and expense. For me, cheap and easy to obtain 95 % effeciency is O. K..Again thanks for doing the comparison, it helps me accept the theory of diminishing returns.
MattI believe his designs are for sale via a PM, because he doesn't want his extensive work to be labled as a sales pitch. (just my thoughts). Keeping the thread separate from sales. FuzzyYes, his gas diode designs are totally different from a "K" baffle, and presumably a lot more scientific. After exhaustive testing and rambling, it was tough for me to draw any simple conclusions, due to the complexity of the subject. Total volume didn't correlate to % of reduction, etc. etc. TKO, slim design scored better than some larger diameter models. Washers, hair curlers & foam ran close to some of the top names in the business.Keep in mind that his research was about "add on moderators" and not on modifying an existing shroud. Although some of the principles should apply, I still found it hard to translate that information into something simple and usable. My biggest take away was length in front of the barrel for baffels matters, and a number of the moderators on the market are close in results.
EdwardMy conclusion was yes and yes. (depending on utilization of that space) Shroud with baffles better than no baffles. Shroud with baffles & moderator on the end was even better. Give that thread a read, I would be interested in your conclusions.My biggest suprise was that the better moderators produced a similar result, even with simple designs. For me, a cheap and effective way to quiet down the Libertys & Freedoms is to do exactly what we are doing. Modify the shroud (or not) and add baffles ( "k" style or cone). Sure, everyone wants a totally silent gun. But staying within the confines of the existing shroud, is cheap, easy and produces an acceptable result for me. Totally backyard friendly in my book, but I'm only shooting 18 gr @ about 920 fps. That will make a difference when you "jack things up a little" 😁.
JamesOrder by phone directly to Crosman. Look up parts number first, google NP2 TRAIL parts diagram. Crosman shipping is a flat $4.00 unless the part is big, or long like a barrel. Prices are very reasonable. Baffle needs the last ring enlarged a little, to slip over the end of barrel. Easy to do with a hand drill. I wrap each end of baffle with a peice of tape for snug fit.
NP214-001https://www.pyramydair.com/product/crosman-np214-001-trail-baffle?a=7784We experimented with these a fair amount at the beginning of the year, this can be found in the "Any importers carry this ..." thread. There is a lot of good info there.
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