Takatoshi Yokota

An aircraft noise prediction model considering meteorological effects on noise propagation developed for air traffic optimization

With the growing transportation demand, the volume of air traffic is already approaching and will soon exceed the capacity limit posed by current air traffic control. Japan Aerospace Exploration Agency (JAXA) has conducted a research project called DREAMS, aiming to develop technologies for future air traffic management system. One of the research topics examined by the project is noise abatement flight technology. It optimizes approach paths considering the meteorological effects on noise propagation. Its key element is an aircraft noise prediction model which can take into account the effect of meteorological conditions on noise propagation. The effect is computed by Green’s Function-Parabolic Equation method and verified by field experiment using an elevated sound source. Aircraft noise is measured around approach flight path for overall verification, and the results show the average and the standard deviations of the prediction error are -0.66 dB and 1.55 dB, respectively. The presentation provides an...

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,...

Noise Propagation Simulation

This chapter shows examples of numerical analyses on various noise propagation problems including outdoor noise propagation, noise barriers, depressed roads, building facades, building windows, and floor impact sound. In each section, considering the features of each problem, methodology of applying the simulation techniques presented in Part I to the practical problem is introduced and the calculated results are illustrated. Some of the calculated results are compared with measured ones and the applicability and efficiency of the analysis method are discussed.

Field experiments on the influences of wind speed and direction on outdoor sound propagation over flat ground

The influences of wind on outdoor sound propagation are investigated both by field experiments and numerical simulations. At first, measurements of sound propagation at a distance of 160 m were carried out under various wind speed and direction. The relationship between vector wind speed and the variation of sound pressure level has been examined not only for the up/down wind conditions but also for the cross wind conditions. Secondly, the short term sound fluctuations were investigated by the use of a high energy impulsive sound generator and a loud speaker as sound sources. Sound propagation up to 300 m was examined with frequency range from 16 Hz to 4 kHz octave band. Finally, the sound speed profiles in the measurement field were estimated by two methods; one was based on the time interval during the sound propagation from the source to the receivers, the other was based on the wind speed at height of 0.6 m, 1.2 m, 2.4 m and 4.8m, and the temperature. By using those sound speed profiles, the excess at...