Figure A. Comparison of sound pressure spectral densities between OP4 (red line) and OP5(blue line) in inlet side (a) and outlet side (b) [6]

From

Low Noise Intake System Development for Turbocharged I.C. Engines Using Compact High Frequency Side Branch Resonators

Sabry Allam

Advances in Powertrains and Automotives. 2015, 1(1), 12-23