Noise Measurement Protocols
Three different approaches to boat noise measurement are currently used in the United States. All are published by the Society of Automotive Engineers (SAE). The NMMA and the Personal Watercraft Industry Association, however, strongly endorse the SAE J1970 method because it better enables enforcement officers to regulate the impact of boating noise on shoreline recreationists and property owners.
The first boat noise measurement method, SAE J34, is intended as an engineering test method that a manufacturer can use to evaluate the effects of design changes, or to determine compliance with state boating noise laws that are often based on this test method. The SAE J34 test method requires the boat to be operated at wide-open throttle (WOT) on a path 50 feet from, and perpendicular to, a sound level meter.
While SAE J34 is an excellent engineering test method, it has limitations when used as an enforcement test method to identify noisy boats in actual real-world use. Many parameters must be rigidly controlled in order for the test results to be valid and defensible in court. To address these difficulties, two other enforcement test methods have been adopted and are placing SAE J34 in state legislation. These tests are SAE J2005 and SAE J1970.
SAE J2005 is also known as the stationary test. It is performed while the vessel engine or engines are at idle, with a measurement distance of no less than 1.5 meters. This eliminates many of the test site variables that make the J34 test difficult. Unfortunately, because this test measures sound at idle, it gives only an indirect indication of the noise level a boat will produce under power. The J2005 test has a recommended limit of 90 dB (A).
SAE J1970 is a completely different approach to measuring boat noise. This test measures the noise received on-shore from operation of any vessel. It involves making measurements at the shoreline and comparing the noise measured to a recommended limit of 75 dB (A). If any individual boat is identified as exceeding this limit, enforcement action can be taken. Under this method, it is up to the boat operator to control the amount of noise from his or her boat. If a boat is quite loud under power, it may be able to meet this limit by operating at low engine RPM and low speed near shore. The theory behind SAE J1970 is to regulate the impact that noise will have on listeners on shore; it does not try to control loud boats, except by pushing their operation farther from shore.
