Silencers continued...

Resonator Silencers
Halyard developed and patented the resonator silencer in 2006, using technology developed in the Helmholtz resonator and adapting this to function in a water cooled exhaust system.  This was achieved over a two year period working with Southampton University.  The silencer is designed to suit the engine configuration (straight four cylinder, straight six, V8 etc) and the cruising rpm involved.  The technology establishes the peak frequency noise output and designs an acoustic “spring” to deal with this.  The result is that the noise peak is effectively cancelled and the overall noise level reduces dramatically.  A recent independent test conducted on a twin engine 65’ powerboat, working to the EC noise test standard ISO14509, showed an average noise level of 74.6 dB(a) – less than half the noise level maximum at 25 metres required by the European Recreational Craft Directive.
cont......