SIDLAB Simulation of a Small Engine Muffler
Schematic of Small Muffler Schematic and Cross Section
Examples of a Small Engine Muffler Simulation and Measurement

Schematic of Small Muffler with two chambers and perforated openings between the chambers.

Transmission loss Data from SIDLAB Simulation and SIDLAB Measurment

SIDLAB Simulation Transmission Loss vs Gas Temperature  By changing gas temperature the acoustic parameters such as speed of sound and wave length change.  The transmission loss shifts to higher frequency.  In the graphic the peak in the transmission loss shifts from 2 kHz @ 20C, to 3.1 kHz at 400 C to 3.6 kHz at 700C.