Silencers

Silencer types and their frequency- range

Absorption silencers
The acoustical energy is transferred into heat in the absorption material. Often used as absorption material is rock- or glasswool. Silencers work a little in mid- and best in high frequencies.

Reflection/reactive silencers
Based on the principles of reflecting, expansion and flattening pulsations. Mostly diameters and internal pipelengths determine the attenuation. Silencers work in low frequencies. No absorption material is used.

Combined silencers
Both above mentioned principles combined in one silencer. First part often reactive, to reduce pulsations in the absorption part. Silencers work in low, mid and high frequencies.

For a wide range of attenuation a two silencer system is advisable. Often used is a SDHC reflection silencer with a HD or HDD absorption silencer. All above mentioned silencers can be combined with a sparkarrester, built-in or loose.

Global (standard)silencer selection

Reference is a 4-stroke engine up to app. 300 kW with a noiselevel of app.
115 dB(A) / 1m. The list below is a guideline, no guarantees can be given.

Backpressure
Often a point of discussion, therefore mentioned:
1000mm H2O ≈ 10.000 N/m2 ≈ 10.000 Pa ≈ 10 kPa ≈ 0.1 bar ≈ 100 mbar