51 Examination on Measured Equivalent Sound Pressure Level and Sensory Evaluation for PWC Operating Sound 2002-32-1820

When evaluating the sound generated by PWC (personal water craft), it is essential to study the measurement method for the PWC sound itself. However, it is equally important to identify the influence on the people in the neighbor of shoreline by being exposed to the sound from a group of PWC running around on waters. Such influence can be grasped in relation to the results of sensory evaluation.

LAeq (equivalent continuous A-weighted sound level) was measured on PWC's running in various patterns and different numbers, while sensory evaluation was performed to obtain the data for the feelings the exposed persons would have about the sound. In this way the correlation between the sound pressure level and its perception by the people were analyzed.

LAeq is the mixture of natural sound at the test site and the sound from the PWC(s) running in the predetermined patterns. We analyzed how the measured sound pressure level changes by the distances from the shoreline and the numbers of PWC's in operation.

SD method (Semantic Differential Method) was applied for the sensory evaluation, in which the persons subjected to the test described the impression of the sound and vibration without his or her visual perception. Twenty six (26) persons took part in the test, and they made an assessment using twenty (20) pairs of adjectives of opposite meanings. Then, the gathered data was processed by varimax rotation in regard to two (2) factors, and the separated factors were named “noisy factor” and “musical factor”. Cluster analysis was performed for twelve (12) running patters, and they were grouped into three (3) clusters. The results of sound pressure measurements and the factor analysis verified the correlation between LAeq and “noisy factor” in person's perception. As expected, LAeq is also related to the distance from the PWC to the shoreline, as well as the number of PWC's in operation.

The finings from these testing will make the good reference material in establishing the requirements to assure the good environmental conditions.