[Amps] Acoustic Noise Comparison

[Jim Brown]

On 6/22/2012 9:19 PM, Jim W7RY wrote:
> Felt works great for soundproofing.

In that application it is acting as vibration isolation -- that is, its 
softness minimizes the VIBRATION coupled to the desk below.  If you put 
a thick felt under the entire typewriter (rather than only under the 
feet), the softness of the felt would ALSO kill the REFLECTION of the 
sound of the typewriter off the desk.  Two different mechanisms.  In 
both cases, thick and soft works best, but in the first case, it must be 
firm enough that it's still a bit "springy" to absorb the vibration.

73, Jim K9YC