Validation case
Muffler with an extended-tube chamber
Against the same model in a commercial finite-element code, for the muffler with an extended-tube chamber, 20 °C, 20–1000 Hz, SpectraSim gives: transmission loss rms 0.12 dB, largest 1.3 dB; the 815 Hz notch at the same frequency.
0.12 dB TL rms difference, 20 Hz to 1 kHz
Results
How close is SpectraSim?
Transmission loss rms 0.12 dB, largest 1.3 dB; the 815 Hz notch at the same frequency.
Model and set-up
- Reference
- The same model in a commercial finite-element code
- Chamber 85.4 mm in diameter and 200 mm long; tubes of 25 mm reaching 100 mm (inlet) and 50 mm (outlet) into it.
- The tube walls inside the chamber are rigid walls of zero thickness.
- Air at 20 °C, anechoic ends, 197 frequencies in 5 Hz steps; SpectraSim’s default mesh.
How to read the result
- Both programs solve the same model: this shows that SpectraSim solves the equations as a commercial finite-element code does, not that the model describes a real muffler.
- The quarter-wave resonance of the extended tubes lands at the same frequency in both.
Selected cases
Other validation cases
-
Measured Concentric-tube resonators ≈ 2 dB peak levels against measured -
Measured Parallel-baffle (splitter) silencer 1.37 dB TL rms difference, 50 Hz to 4 kHz -
Analytical Pod silencer with absorbing pod and lining 1.3 dB TL rms difference below the 1.7 kHz cut-on -
Code-to-code Exhaust muffler with three absorbing packings 0.16 dB TL rms difference, 20 to 500 Hz -
Analytical Expansion chamber against the exact 1-D solution 0.36 dB below 0.4 of the first cross-mode cut-on
Check it on your own muffler.
Download SpectraSim and run your geometry, or let our engineers run the study and compare it with your test.