In this paper, we revisit the acoustics education program using mobile devices to better understand urban environments. We begin with a summary of our past projects to demonstrate a model case of the concept. In these projects, the output was mainly supposed to be a noise map with measured sound pressure levels (SPLs) and sound spectra. This methodology can obviously be applied to larger-scale urban studies. Including measured sound spectra can be another advantage. Next, current problems in measurement accuracy due to recent device developments are explained and the required examinations are stated. Finally, the accuracy of the current versions of the applications as well as recently available devices are discussed. The results of this study provide information regarding the measurement accuracy of mobile devices, and some suggestions for their practical use are given, which are also useful for additional studies pertaining to the urban acoustic environment.

In an introductory course for environmental/architectural acoustics in universities, it is often used the teaching method based on soundscape, in which students are asked to make a sound map with listening their surrounding acoustic environment. However, if objective measurement of sound pressure level or frequency spectrum can be introduced in such a course, it will interest students in environmental acoustics, and enable them to discuss the acoustic environment more profoundly. Measurement apparatuses are usually expensive and difficult to be used in such a course. Therefore, we consider to use a smartphone: using a smartphone with acoustic measurement applications, it can be possible to introduce an objective measurement in such an introductory course for beginners. In this study, first some applications for acoustic measurement are examined to confirm their accuracy as well as the effect of a simple handmade windscreen. Secondly, using suitable applications, as a possible work in the course, sound maps with measurement results by a smartphone are made and their examples are shown. Finally, some issues to introduce this method in actual courses are discussed.

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Geo-referenced sound data are often used in the field of acoustics education to learn about the urban acoustic environment. Simple soundwalks and sound collections are also employed, in which acquiring additional information such as visual data, recorded sound data, and GPS location data are helpful to produce a map with sound data and sound collection and to carry out more profound discussions in educational activities. In order to enrich these acoustic educational and environmental survey activities with a simple tool, the use of multifunctional sound-pressure level (SPL) measurement applications with mobile devices are proposed. Some experiences of combined activities of the above methods using the applications and mobile devices are reported in this paper. In this study, applications for SPL measurements, which record GPS location data, sound, photo, and video during measurements, were used to produce geo-referenced sound data. First, the accuracy of the applications was checked and we found them to have reasonable accuracy when used with iOS devices; for example, the averaged error was less than 1.5 dB(A) with iPhone XS. Next, they were actually used in a simple soundwalk-like field survey and the resulting geo-referenced sound data were presented to discuss the merits and demerits of each application. Overall, the applications used in this work were found to be useful; for example, recorded sound allowed us to check the main sound source and to carry out discussions using collected sound samples later, and photos and videos allowed us to grasp the impressions and situations around the measuring points. Therefore, these multifunctional sound level meter (SLM) applications can be effectively used for various purposes, including acoustics education for learning about urban acoustic environments.

The municipal public address (M.P.A.) system for disaster prevention is an important information facility in communities. The speech intelligibility of such a system, however, tends to be deteriorated by multipass echoes with long time delay owing to reflections from nearby buildings and by the sounds from loudspeakers covering other subareas. When designing such an M.P.A. system, a tool effective for the prediction of outdoor sound propagation should be developed. For this purpose, the authors have been investigating the applicability of a computer modeling technique based on geometrical acoustics. To elucidate the effectiveness of the modeling technique, two case studies were examined by comparing impulse responses (echo diagrams) calculated by computer modeling and those obtained by field measurements. As a result, it was found that this modeling technique can be effectively applied to the prediction of outdoor sound propagation and the basic design of M.P.A. systems.