Figure 11. Amplification of sound for the resonator shown in Figure 2(e) at different Mach number.(a) M=0.025, (b) M=.05, (c) M=0.1, do=0.037 m

From

Experimental Assessment of Noise Generation from I.C. Engine Intake and Exhaust Systems Components

Sabry Allam

American Journal of Vehicle Design. 2015, 3(1), 6-15