Seamanship: Unsafe and Sound

The not-so-silent killers: noise and vibration.

After a 40-mile run back from the offshore fishing grounds, my buddy let his concentration waver in the inlet and stuffed the bow of his center console. The water rushed in and nearly sank his boat. He chalked it up to letting his guard down close to home, which is partly true. What he ignored was the hidden disabler: noise-induced fatigue.

No matter what kind of boating you do-cruising, fishing, or poker runs-you're exposed to a high-noise environment. Sound, and its partner vibration, comes at you from the engines and the wind. It can sap your strength and impair your judgment. So it's wise to be aware of how noise affects you and how to handle it.

Underway, you're exposed to the low-frequency waves emitted from your boat's engine. These waves literally slam into and bounce off your body, wearing you down physically. They are one reason why, even after lounging on an airplane for two hours, you feel tired.

High-frequency sound waves from your engines and the wind have a psychological effect. The louder these noises are, the harder it is to concentrate. You exert more energy just to talk or listen to someone else. Studies show that exposure to sounds of 90 dB-A or higher can cause increased blood pressure and a raised heartbeat, as well as nausea and fatigue. Loud noises also make you irritable and decrease your attention span.

To put boat sounds into perspective, take a look at the reference chart from the National Institute for Occupational Safety and Health (NIOSH) at www.cdc.gov/niosh/01-104.html. Normal conversation falls in the 60 dB-A range whereas irritating lawnmowers and belt sanders reside in the low 90s. According to NIOSH, any continual noises over 85 dB-A must be regulated in the workplace. On a boat, hopefully far away from work, there are no such regulations. Keep in mind that the decibel scale is exponential-a jump of 1 dB-A produces three times the sound energy.

I took a sampling of sound readings measured at the helm during our Certified Boat Tests, averaging the numbers from 25' to 30' center consoles, 20' to 24' runabouts, 30' cruisers, and 40' to 50' motoryachts. At 3500 rpm, the low end of the cruising range, an average for center consoles is 87 dB-A. Throttle to 4500 rpm and the average jumps to 90. On a runabout, the average at cruising rpm is 88; for a cruiser, it's 85. A motoryacht with an enclosed helm sees a more comfortable cruising dB-A of 73.

So how does this affect you as you zip around for the day, take an extended cruise, or fish for a few hours? You can lose your concentration while navigating, entering an inlet, dealing with traffic, or doing a complex task such as docking. That loss of focus may cause something minor such as scuffing your rubrail at the fuel dock or something major such as missing a marker and running aground.

What can you do about noise? Create a system to prevent or reduce fatigue while onboard. If you're going to cruise for any length of time, take turns behind the helm. Common practice for standing watch on commercial and military vessels calls for four-hour shifts. But this system is intended for people with a lot of time at sea. You're better off limiting time at the helm to two to three hours at a crack. If no one else aboard can handle the boat, include breaks in your cruise plan. Earplugs can help, from 50-cent foam plugs to more expensive custom-molded ones, but they aren't a cure-all. The best can cut noise by 30 dB-A while allowing you to hear your crew, radio transmissions, and warning alarms. Whatever you do, try to keep it quiet-and don't space out in the inlet.

Boating Writers International 11th Annual Writing Contest - Peter McDonald's "Seamanship" won 1st place in the Boating Columns category.