In the world of generators, a silencer performs the same function for combustion engines as the muffler does for engines in automotive and construction applications. Both reduce noise and exhaust emissions produced during combustion.
There are three basic designs of silencers:
Reactive Silencer - Internal construction consists of up to three chambers connected by a tube. Exhaust noise bounces between the chambers reducing output noise. Used for low to mid-frequency noise reduction.
Absorptive Silencers - Internal construction consists of fiberglass or E glass insulation. Exhaust noise is dampened as it flows through the insulation. This method is used to reduce high frequency sound waves.
Combination Silencers - As implied, combines the construction of the reactive and absorptive silencers. Absorption material is fitted into the chamber design of the reactive silencer. This allows reduction of all frequency designs.
Cylindrical Silencers
Cylindrical silencers were among the first shapes developed. They can be constructed to all three basic designs and used both on inside and outside applications. The silencer can be mounted horizontally or vertically to satisfy any application requirement. It is considered one of the most economical silencers.
Sound Rating for Generator Silencers
The sound intensity emitted from an exhaust system is measured in Decibels (dB). The dB is a unit of measurement used to express the ratio of one physical property to another represented on a logarithmic scale. Decibel A Weighted (dBA) is measurement used to approximate the human ear response to sound.
In the early days of rating silencers, there were four basic grades. Industrial, commercial, residential, and hospital grades were considered the industry standard in silencer manufacturing. During this period, the amount of sound reduction for grade varied between manufacturers. The Electrical Generating Systems Association (EGSA) developed a rating guide that provided consistent silencer ratings for any manufacturer belonging to the association. This has become industry standard for manufacturing.
Common grades are:
Industrial Grade - Exhaust noise reduction of 15 to 20 dBA
Residential Grade - Exhaust noise reduction 20 to 25 dBA
Critical Grade - Exhaust noise reduction of 25 to 32 dBA
Super Critical Grade - Exhaust noise reduction 30 to 38 dBA
Hospital Grade - Exhaust noise reduction of 35 to 42 dBA
Hospital Plus Grade - Exhaust noise reduction of 35 to 50 dBA
Extreme Grade - Exhaust noise reduction of 40 to 55 dBA
Super Extreme Grade - Exhaust noise reduction of 45 to 60 dBA
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