Sakae Yokoyama

Subjective experiment on suitable speech-rate of public address announcement in public spaces

In such public spaces as railway stations, airport terminal buildings, shopping arcades, etc., it is often the case that information provided through public address (P.A.) system is deteriorated by the influences of reverberation and background noise. This problem is serious especially for the case of providing various information and emergency evacuation alarms in the case of such disasters as earthquake and fire. Regarding this acoustic problem in public spaces, the authors performed field surveys in various public spaces, in which actual P.A. announcements were recorded and reproduced in an anechoic room by applying the 6-channel recording/reproduction technique to realize 3D aural impression. As a result of the subjective experiments on speech intelligibility (ease in listening) performed in the simulated sound field, it has been found that the speed of speech is an essential condition as well as reverberation and noise level. To investigate the way of improving speech intelligibility in such spaces, ...

Binaural simulation using six channel reproduction based on the finite difference time domain room acoustic analysis

For auralization of room acoustics, various simulation-reproduction systems, such as ray tracing, cone tracing, image source methods, and wave-based numerical analysis for sound field simulation, and transaural system, multi-channel loudspeaker system for sound field reproduction, have been developed. As a sound recording-reproduction system, the six channel system has been developed, in which a sound signal is recorded by orthogonally located six directional microphones having a cardioid characteristics and the recorded signals are reproduced by orthogonally arranged six loudspeakers. To obtain binaural signals for auralization with headphones, the six channel reproduction was combined with binaural recording using dummy head microphones. The proposed concept can be efficiently applied to room acoustic simulation. As a room acoustic calculation method, finite-difference time-domain method was employed in this study. The calculated room impulse responses were reproduced by six channel reproduction system,...

Auralization of municipal public address announcements by applying geometrical sound simulation and multi-channel reproduction techniques

Municipal public address system (M.P.A. system) for disaster prevention is an important system for supplying information outdoors. The speech intelligibility of the M.P.A. system, however, tends to be deteriorated by long-pass-echoes due to reflections from the surrounding buildings and the sounds from the loudspeakers covering other sub-areas. When designing such a M.P.A. system, effective tools for prediction of outdoor sound propagation are needed. For this aim, the authors have been investigating the application of the sound simulation technique based on geometrical acoustics. In addition, auralization is also desirable to subjectively assess the speech intelligibility of the M.P.A. system in acoustical design. Therefore, the authors are developing a simulation technique in which the sounds calculated by the geometrical simulation are reproduced through a 6-channel reproduction system, by which 3D information can be aurally realized. In this paper, the outline of this simulation method and some exampl...

Subjective experiment on preferable reverberation of a musical practice room by professional players

A musical practice room is very important space for players to improve their skills. However, no architectural design guideline of the musical practice room exists in Japan and the individual room is being designed based on architects intuition and experiences. For a basic investigation aiming to establish the guideline, we are now investigating appropriate acoustic conditions of musical practice rooms for players by subjective experiments. In this study, we focused on reverberation time of the room and subjective experiments using a three dimensional sound field simulation were conducted for professional players including woodwind instrument players, string players and singers. In the experiment, a room having 6 conditions of reverberation time was virtually simulated in the sound field simulation system established in an anechoic chamber. As a result, a clear tendency of preferable reverberation time dependent on the difference of types of the instruments was found and a range of preferred reverberatio...

Design of public address system for emergency evacuation in a tunnel

As a means to improve speech intelligibility of a public address PA system for emergency evacuation announcement in a tunnel, the authors have been investigating the application of the successive time‐delay technique and have performed the experiments in an actual tunnel. In the experiments, the effect of the technique has been examined by comparing the difference of speech intelligibility between the conditions with/without time delay. For the design of the PA system in a reverberant tunnel, four kinds of psycho‐acoustical experiments on speech intelligibility were performed in an anechoic room using the six‐channel recording/reproduction technique and the following results have been obtained: (1) the successive time‐delay technique is very effective to improve the speech intelligibility in a tunnel, (2) the system is considerably robust against the error in the delay time, (3) the speech intelligibility improves with the increase of the speech‐rate but it should be suitable for such a tense situation as...