The adequate sound levels for acoustic signs for the visually impaired under the sound environment with advertising sounds on the street were measured through a psycoacoustic experiment to reveal the effect of the advertising sounds such as the ambient music from shop, advertising announcement, and so on. The participants were asked to adjust the playback level of the each acoustic sign to an adequate level by using the fader of the sound mixer while comparing to the background sound levels. The experimental results showed that the estimated adequate sound level for the acoustic traffic signal was approximately 21 dB higher than the environmental sound level, while that for the guidance chime was approximately 17 dB higher than the environmental sound level. The results also revealed that the difference between the estimated adequate level and the environmental sound level were higher in contrast to the sound environmental condition that was mainly comprised of road traffic noise. These results suggest that the consideration under the varied sound environment are required in time of designing the acoustic signs for the visually impaired.
In railway transport, it has been recently increasingly demanded to reduce the rolling noise that accounts for a great portion of the track wayside noise by a method easy to execute. Therefore, we have developed a new type device, called Rail Noise Isolating Material (RNIM). RNIM consists of two laminated layers, the inner one of which is made of viscoelastic sheet ; and the outer one of high modulus plate. In order to select the materials suitable for RNIM, the impact test was executed against several samples made by representative practical materials. As the test results, ethylene-propylene rubber (EPDM) foam was selected for the inner layer ; and damping or normal steel, for the outer layer. The noise reduction property of the selected sample (the damping steel for the outer layer), was examined by measurement of track wayside noise among train passage on a commercial line. As the result, it was found that the noise reduced by 2～3 dB with installation of RNIM.