Regardless of the content of the sound, it can be quantified using a meter that measures decibels (dB). The smallest difference in noise level that most humans can perceive is 2 dB, while 100 represents the threshold of pain.

The decibels are measured on a logarithmic scale, that is, the value of a dB is not a constant. Ten decibels equate to a tenfold change. In other words, 100 db is ten times louder than 90, and one hundred times louder than 80 (10 x 10). Keep that difference in mind when you compare boats – an apparently small difference, say 75 dB compared to 85, can make a huge difference.

As a point of reference, inside a car traveling at 70 miles per hour on a smooth road the sound level would be about 68 to 70 dB. Standing near the runway of an airplane taking off would produce about 115 dB. An exposed running boat engine would produce about 100 dB.

If you put a simple enclosure around the exposed boat engine, the dB level would drop from 100 to 90. All modern yachts have some level of sound insulation around the engine compartment. With a reasonable effort a boatbuilder can reduce the sound level to the mid 80’s. On the Zimmerman 36 we go well beyond the common practice, and the effectiveness of our approach can be seen in the results: 75 dB at seventeen knots. Compared to a boat with a sound level of 85 dB, your ear would perceive that boat to be twice as loud as a Zimmerman 36.

In addition, noise occurs at different frequency levels, and an acceptable dB level for one frequency might be unacceptable at another. Some low frequency sound, such as that emitted by a muffler, can be felt as well as heard. For this reason, we insulate such components from the hull, in order to minimize vibration.

A smoother quieter boat produces less fatigue. At 75 dB you can have a normal conversation in the main cabin while at cruising speed. With a trend toward quieter boats, the extra effort spent on building the Zimmerman 36 will payoff in helping with resale value. So, you get to enjoy the difference while you own the boat, and when you sell her.