Pilot study on acceptable sound levels in scenic areas

Abstract

The intrusion of road traffic noise in scenic areas is one of the key issues in managing acoustic quality. Several studies focused on acceptable sound levels for road traffic noise in such areas; however, most of them estimated acceptable sound levels from the dose-response relationship between sound levels and annoyance or evaluation of acoustic comfort, and few studies investigated acceptable sound levels directly. We directly investigated the acceptable sound levels for road traffic noise in scenic areas in Japan by conducting psycho-acoustic experiments involving a group of participants. Two simulated road traffic noises were used as target sounds, and four audio and video recordings were used as background conditions. By a method of adjustment, the participants were required to adjust the playback level of each target to a maximum acceptable level while comparing the background sound levels. The results showed that the acceptable sound levels cannot be explained by a simple value or a simple signal-to-noise ratio (SNR). There is a clear tendency that a higher SNR, which means that road traffic noise can be heard more clearly, is acceptable in a quieter area. The acceptable sound levels of scenic areas are largely dependent on the evaluators and features of the areas.