Additive Manufacturing of Silencers with Microperforates

Table 1

Three MPP-gap options tuned to 3500 Hz.

	MPP parameters				Cavity/Gap
Option	Perforation ratio	MPP thickness t	Hole diameter d	Perforate constant in air at 3500 Hz	Backing cavity depth D
A	5.0	1.0	0.3	5.8	8.0
B	7.0	1.5	0.4	7.7	8.0
C	10	1.5	1.0	19	9.7

Note that option C is, strictly speaking, not MPP because hole diameter is 1 mm.