Japan develops silencer

The Japanese NMRI (National Maritime Research Institute) and fire protecting door and noise-proof package manufacturer Taiko Sangyo have developed a new silencer system that dampens low frequency noise from diesel engines. This noise pollution emanates from ships berthed in port areas and is particularly noticeable at night when the humming produced by diesel generators becomes distinctly perceptible.

In 2002, the NMRI and Taiko Sangyo started a joint research project intended to develop a practical solution to the problem. Preliminary results from a prototype system have been very promising and the two organisations have applied for a patent and are now working on ways to commercialize the system.

The system comprises of a phase adjusting unit which equalizes the esound pressure propagation distancef in the exhaust pipes of a diesel engine, and the new type@ (expansion/absorptive type) silencer. In tests using a diesel generator, sound levels were reduced by 10 dB when fitted only with the phase adjusting unit, and by 15 dB when fitted as a full system, i.e. the phase adjusting unit and the new type silencer.