Additive Manufacturing of Silencers with Microperforates

Figure 3

Sound pressure distribution in a Cremer silencer duct (length 240 mm, diameter 34.8 mm) excited at left end using sound pressure level of 94 dB. Top: rigid duct wall. Bottom: locally reacting duct surface; tuning frequency 3500 Hz. Note that the scale is different, because the incident wave does not propagate well. It decays over 40 dB in the first 50 mm.