One of the provisions of the Recreational Craft Directive (RCD) requires marine crafts to comply with designated noise levels depending on the design category. Usually, this is done by conducting sound tests, as prescribed by the ISO 14509 directive. The sound test is required for fast water crafts that are 24 meters or below in length. Slower marine crafts need not undergo any sound test, as CE proofing procedures can simply compute for their output.
RCD sets the standard sound level for all marine crafts at a range between 67 and 75 decibels. Simply put, the boat subject for CE proofing must be as loud as a vacuum cleaner when one stands near it. The standard sound level for marine crafts depends on the power output of the engine. Considering that some places in Europe are usually quiet, the marine craft must not create too much noise.
The sound test itself is very simple: a microphone will record the sound of a boat traveling at a speed of 38 knots or 44 miles per hour. The microphone can either be fixed onto a buoy or on a second boat. The test is carried out in open waters for the boat, traveling one nautical mile or almost two kilometers for the test, to maneuver better. The test will find out the maximum sound level the boat can achieve.
To get an accurate result, the boat and microphone must at least be 25 meters from each other when the boat makes its pass. The information from the test is then evaluated by a Notified Body in which all 21 of them are based in Europe. The Notified Body is the assessor for certain products prior to giving them CE proofing, including marine crafts. Getting the approval from these bodies is tantamount to getting the CE marking for your boat.
Marine crafts with exhaust systems located below the water are quieter because the water is a natural muffler. However, for boats whose exhaust systems are above the water need to have mufflers installed to reduce their noise levels. Mufflers work by creating an opposite sound wave pattern to fit that of the exhaust noise. Following the concept of destructive interference, two opposing sound waves cancel each other; thus, reducing noise.
CE proofing is a lengthy process and the sound test for marine crafts alone takes up a lot of time. However, passing this test brings the boat significantly closer to being approved for travel within European waters. By keeping the engine noise down, you can have a safe and noise-free trip from shore to shore.