Estimate silencer insertion loss by octave band for engine exhaust and inlet noise, per ISO 9613.
| Parameter | Formula |
|---|---|
| Geometric Divergence | Ldiv = 20 log10(r) + 10 log10(4π) |
| Silenced Lp | Lp = Lw - Ldiv + DI - αr |
| A-weighted Sum | LA = 10 log10(Σ 10(Li+Ai)/10) |
| Noise Reduction | ΔL = Lunsilenced - Lsilenced |
Understand silencer types, DIL testing standards, and octave-band noise analysis methodology
DIL is the reduction in sound level measured at a specific point when a silencer is installed in the system, expressed in decibels per octave band frequency.
It subtracts manufacturer DIL values per octave band from unsilenced sound levels, applies geometric divergence, atmospheric absorption per ISO 9613-1, and stack directivity corrections to predict noise at specified distances.
Octave-band analysis provides frequency-specific detail essential for proper silencer selection, as silencers have different insertion losses at different frequencies. Overall dBA alone can mask deficiencies in specific frequency ranges.