TOA Corporation

In Japan, public address announcements for life-threatening evacuation guidance are regulated by legally binding standards, ensuring minimum quality. However, for general public address announcements, various speech intelligibility indices have been proposed and standardized, but their application in public spaces is optional. Moreover, in spaces such as stations, airports, and commercial facilities, few criteria for these indices have been defined. Thus, even if measured, it is difficult to objectively determine whether the sound quality is adequate. Consequently, the skills of manufacturers, designers, and installers involved in public address systems are not appropriately recognized in terms of acoustic quality. Similarly, owners of public spaces cannot assess whether the announcement quality in their facilities is sufficient. Although these indices can be predicted through simulations and designers propose systems based on these predictions, owners with limited acoustic knowledge may find it difficult to judge their reliability. This often results in hesitation to adopt costly systems, and many public spaces end up with low-quality announcements. While evaluation indices exist, their meaning is not widely understood socially and has not led to quality improvement. This presentation discusses the introduction of a certification framework and an independent third-party certifying body for general public address announcements to improve quality and contribute to creating more comfortable public spaces.

A continuous measurement method is proposed for room impulse responses using maximum length sequence (MLS) signals, allowing efficient estimation of frequency responses at multiple locations during motion. The proposed method extracts the averaged impulse response over the measurement trajectory within one period of the MLS signal. Experiments conducted in an anechoic chamber and an ordinary room at a walking speed of 0.5 m/s using a 15th-order, 48-kHz MLS confirmed that the transfer function obtained via this method closely matched that obtained from conventional measurements. The maximum deviation across the third-octave bands was less than 3 dB, and the standard deviation was approximately 1 dB. These results demonstrate that the proposed method can capture room acoustic characteristics effectively.

This study investigates effects of grass on hydro-thermal-mechanical properties and shallow stability of unsaturated soil slope. A field measurement consisted of two cut slopes, namely bare slope and grassed slope, was carried out. Field measurement results show that grass has effects on reducing the volumetric water content and increasing matric suction. There is a greater gap in matric suction between grassed soil slope and bare soil slope when the snow appears. Besides, the soil temperature in grassed slope is lower than bare slope in warm seasons. However, contrasted result of the soil temperature is recorded in winter. The triaxial tests were conducted for studying mechanical properties of grassed saturated soil with different grass ages. Experimental results reveal that there is an increase in peak shear strength and effective cohesion of grassed soil as the grass age increases, whereas a slightly higher effective angle of internal friction is observed. Furthermore, the volumetric strain decreased with the rise in grass root volume ratio. The approach of coupled nonisothermal-seepage numerical analysis for unsaturated soil slope considering impacts of grass is suggested. It is followed by slope stability analysis considering enhanced shear strength of soil due to grass roots. The good agreement regarding soil temperature and volumetric water content between simulation and field measurement indicates that the proposed approach is feasible to consider the influences of grass on the hydro-thermal behaviors of unsaturated soil slope. Furthermore, the higher values of factor of safety (FOS) of grassed slope present that the grass is effective in resisting the shallow landslide-prone area.