*          For sizes 4” – 12” Nelson level “300”, use Maxim model M31

**        For sizes 14” and larger Nelson level “300”, use Maxim model M41

All silencer designs will perform differently depending upon the characteristics of the engine, the exhaust system layout, and the gas velocity and temperature within the silencer. This enables some tests to be performed in which an inferior silencer can be made to appear to out-perform a superior silencer.

The fundamental firing frequency of most stationary reciprocating engine and marine engine applications is in the 60 to 300 hertz range.  Maxim silencers are optimized in internal design geometry to provide the best overall attenuation possible in this frequency range to offer predictable, dependable attenuation of both high and low frequency noise.  For over 100 years, Maxim’s experience in this field enables us to confidently rate our indicated models as being equal to or better than the competitor's silencer models shown in the cross reference table.

Most silencer designs will be reactive (chamber) types in which no absorptive materials are used.  These can be made very effective in the low frequencies with effectiveness also extending into the mid and high frequencies by including more chambers or by incorporating special internal features. Reactive silencers are popular for the following reasons:

• The reactive silencer will not lose effectiveness with time due to internal fouling or loss of acoustical media.

• Most reciprocating engine exhaust noise has a fundamental frequency in the low frequency end of the spectrum where the reactive silencing design feature is most effective.

• The performance to cost ratio for reactive silencers used in reciprocating engine exhaust service is higher than for the other types of designs.

This chart compares other silencers with Maxim silencers of either chamber type silencer designs utilizing two or more chambers or straight through designed silencers utilizing acoustical packing material.

The volume occupied by a given silencer size (nominal pipe connection size) tells much about how effective that model can become if its internal design is optimized for a specific application.  The general rule is that a given silencer model can be made more effective if it can have its volume increased:

• Larger body diameters enable higher amounts of noise reduction at all frequencies.

• Longer silencer lengths can also enable more noise reduction, especially in low frequency bands, because chambers are made longer or because more chambers are added.

A decision as to whether to add more chambers or whether to make the chambers longer must be decided by analysis of the un-silenced exhaust noise spectrum of the engine. Simply adding more chambers or other internal features without increasing the volume occupied by a silencer will not increase the noise reduction.  In many cases, the performance will be decreased.  In some non-typical engines that have fundamental frequencies above 300 hertz or that have a higher than usual amount of high frequency noise, a smaller silencer that has more chambers or one that uses acoustical packing may be tested to compare favorably with a larger Maxim reactive silencer. However, it should be known that in the majority of typical reciprocating engine applications, the Maxim units will perform better than any smaller silencers or silencers of the same size that have been divided into more chambers.