1. An Octave Band split the audible spectrum into smaller bands, identifying the frequency content of the noise.
2. DIL = Dynamic Insertion Loss
(difference of two Sound Power Levels)
e.g.
the unsilenced noise level of a valve is 150dB(A)
the silenced noise level (at the silencer) is 120dB(A)...
It is possible to feed different flows into one silencer, even at simultaneous flow and different inlet pressure.
This can be achieved with diffuser pipes.
diffuser pipe
collecting pipe
silencer with two inlet diffuser pipes
www.ventsilencer.com