Wind Horse is exceptionally quiet under way. She is easier on the ears, in fact, than was Beowulf at the same average speed under sail. Still, in spite of a minuscule 57dB at cruising speed we have been slowly fine tuning the sound levels.

Machinery noise from our little John Deere diesel engines is almost nonexistent in the salon. But we do pick up a bit of exhaust noise from the outside. This has gradually been reduced to a low frequency ambient, just above our sense threshold.

We guessed that this was a tuning issue between the two exhausts and we have been experimenting with various methods of altering the frequency. This past summer we tested changing orientation of the exhaust elbows. What you see above is the third try.

The resonance that used to occur in the exhaust is now 95% gone, and we are even quieter now than the originally measured 57dB.

We suspect that some sailboats will benefit from tuning exhaust frequency with extensions or elbows. The cost of the fittings is low, and they are easy to fit, as log as you have an exhaust extension off the transom.