Soundscape

PWC are no louder than other motorboats, and in many instances are quieter. There are two components creating the sound heard from PWC: (1) the engines during normal operation of the PWC; (2) the water splashing against the hull and resonating.

The Society of Automotive Engineers (SAE) developed three methods of measuring watercraft sound, including that of PWC:

• SAE J34: The most precise measurement available, taken of a boat at a distance of 50ft with wide-open throttle (the near maximum noise of the boat). Although great for engineering standards, it is difficult for enforcement purposes in the field. The Coast Guard recommends 86 decibels (dBA), which most states have adopted as law.

• SAE J2005: This measures the engine sound at idle with the microphone 1.5 m away. SAE recommends a limit of 90dbA for this method, which does not account for the speed or power of the boat.

• SAE J1970: In realizing the enforcement difficulties of the previous methods, SAE designed this shoreline noise test enabling regulations keeping the boat under 75 dBA at 50 ft. by operation, not mechanics. The operator is responsible for controlling the noise of the boat.

The personal watercraft industry has reduced engine sound pressure levels up to 70 percent since 1998. These reductions have been achieved, in part, by lowering the sound made as well as the pitch of the engine. Loudness of sound is a quantifiable term, measured in decibels (dBA). Pitch is a measurement of the frequency that the sound wavelength vibrates. Methods employed by manufacturers to absorb or block the wavelengths of sound greatly lessen both the loudness and the pitch attributed to personal watercraft⁸.

To reduce sound levels, the newest models of personal watercraft utilize air intake resonators with multiple maze-like chambers. These chambers eliminate a direct path for the sound waves to escape⁹. The resonators employ several different length tubes attached to the exhaust pipe. As sound waves pass into these tunnels, they bounce back and cancel out incoming identical but opposite “crest” waves¹⁰. Baffles are also used for counter frequency and to quiet vibration.

Manufacturers also employ noise-absorbing materials between the liner and the hull, so the boat is quieter and more durable. Additionally, some manufacturers have increased the thickness of the crankcase wall to muffle noise and vibration. Rubber is also used as padding around the jet pump dampers to absorb the shock loads and quell driveline noise¹¹.

Critics of PWC claim that PWC repeatedly leave the water, leading to increased sound and annoyance levels. The majority of today’s PWC do not leave the water at all, let alone with any frequency. This is in large part due to the design: newer models are longer, wider, heavier, and have additional seating capacity. Because of these features, newer models leave the water much less regularly than older craft. Three-person PWC -- which account for more than 75 percent of new sales -- can weigh as much as three times more than first generation single-person, stand-up models and are much less apt to leave the water.

The sound created from water hitting the hull is a considerable portion of the overall sound of any running watercraft. In 1994, the International Council of Marine Industry Associations (ICOMIA) Marine Environment Committee (IMEC) tested the sound levels of boats without the engine running to quantify the level of sound generated by the water splashing against the hull of the boat as it moves through the water. The IMEC test results showed that a PWC towed by a 150 meter (492 feet) rope without the engine running measured 68 dBA when measured from 25 meters (82 feet) at a speed of 70 k/mh (44mph)¹². When tested with a running engine at full throttle, the sound of the engine plus the sound of water hitting the hull registered between 72 and 78 dBA, well below the SAE J34¹³ standard of 86 dBA, measured from 50 feet at full speed. The U.S. Coast Guard recommends states adopt 86 dBA as a maximum sound-level.

Objective, scientifically-based sound testing has always found PWC sound levels comparable to other motorboats. In sound level testing conducted on Lake Powell (Glen Canyon National Recreation Area on the Utah/Arizona border) the test data indicated that the maximum sound levels of PWC were actually lower than the maximum sound levels of other motorized vessels. In particular, the levels for PWC at 82 feet were approximately 68 to 76 dBA, whereas the levels for other motorized vessels at 82 feet were approximately 64 to 86 dBA. The National Park Service standard for sound levels is 82 dBA at 82 feet, and the NPS has correctly recognized that unaltered pre-1998 PWC and current PWC are capable of meeting that standard, as well as the more stringent standard of 75 dBA as measured from the shore, regardless of operation (SAE J1970)¹⁴, which is called for in the National Marine Manufacturers Association’s Model Noise Act¹⁵. Independent, unbiased sound testing conducted for the Tahoe Regional Planning Authority and the New Jersey State Police have found similar results.¹⁶, ¹⁷

Additional sound testing was conducted in France by the International Council of Marine Industry Associations in 2003. These tests were conducted to confirm that PWC could comply with recently enacted European Union regulations, and used the same PWC available for purchase in the U.S. The test results found PWC sound levels were between 70–73 dBA when measured from 82 feet with the PWC traveling at 44 mph. These latest test results are consistent with U.S. test results, and continue to confirm PWC manufacturers have made remarkable advances in sound reduction, making PWC among the quietest vessels on the water today.

For more information on PWC and Sound, click here.

⁸Personal Communication, Harry Klemm, Group K, Mohave, Arizona, 2001.
⁹Yamaha Watercraft. “The Yamaha Sound Suppression System and the Yamaha Platinum Plus System” Brochure, 1999.
¹⁰Bombardier Recreational Products, “Bombardier Announces Quieter Watercraft for 1999,” Press Release, 1997.
¹¹Kawasaki Motor Corporation. “Kawasaki Marine Engine New Technology for Year 2000 and Beyond,” Press Release, 2000.
¹²ICOMIA Marine Environment Committee. “Powered Recreational Craft Sound Level Test Report - Lake X, Florida, 1994.” May, 1995.
¹³SAE J34 establishes test procedures for the U.S. Coast Guard that measure sound levels from a non-shoreline location of boats operating full throttle at a distance of 82 feet (25 meters).
¹⁴SAE J1970 establishes the procedure for measuring the sound level of pleasure motorboats at a position on the shore under conditions other than stationary mode operation.
¹⁵NMMA Model Noise Act
¹⁶Tahoe Regional Planning Authority. “Environmental Noise Analysis, Lakeland Village Watercraft.” Brown-Buntin Associates, Inc. September 1992.
¹⁷New Jersey State Police. “Boat Noise Tests Using Static and Full Throttle Measurement Methods.” Noise Unlimited Inc. November 1995.