Figure 9. Amplification of sound for the resonator shown in Figure 2(d) at different Mach numbers. (a)M=0.05, (b) M=0.1, din=.034m

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