At 19:48 3/14/00, Jim Adney wrote:
On 14 Mar 00, at 7:14, Erkson, Toby wrote:> Speakin' o' which, I need some recommendations for what to use. Needs to be> a good sound absorber, water-proof, and light-weight. Suggestions? Good sound absorption requires mass. There's no such thing as a good light sound absorber. Tar, or anything with tar in it, is pretty good.
============================>Multiple layers of thinner materials having differing densities will work well, also. Many times, a "thick" mass will just change the frequency of vibration sounds, and do little to lessen the dB level. Alternating layers of thin sheets of material which will have differing frequency resonances will often work quite well for sound deadening, without adding much in the way of shell thickness or weight addition to the overall structure. Noise is an erratic audio source, whereas "sound" has a pattern. Many times, what we are doing in VW buses and cars is trying to lessen vibration "noise" which is actually "sound", having a frequency and wave form pattern that can be attacked with proper material designs and application. Thickness and "mass" can often be the improper media for attacking "sound".
Bob Perring ===================================== "A Ras Mass is a High Mass" __________ (E[__][__]|[_]\ | __ | *|__||] =-/(O)\-----/(O)\= Home of: Casper, der Freundliche Bus & Otto, der Auto mailto:perring@pdq.net Home Page: http://freeweb.pdq.net/perring ------------------------------------------------------------------- Search old messages on the Web! Visit http://www.vwtype3.org/list/