Use of Mobile Devices with Multifunctional Sound Level Measurement Applications: Some Experiences for Urban Acoustics Education in Primary and Secondary Schools

Abstract

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.

A note on the acoustic environment in a usually quiet residential area after the ‘state of emergency’ declaration due to COVID-19 pandemic in Japan was lifted: supplementary survey results in post-emergency situations

“…The technical information of the NoiseCapture app is available on its web site [9] and documented in [10]. Before the measurements, the app and the device were calibrated using a standardised sound level meter (SLM) (Class 1), and its validity, confirmed via the method in [11,12], was reported in [8]. The results of a sound map made via soundwalk with this app give the noise level range (dBA, L Aeq ) along the soundwalk course.…”

“…It was calibrated and checked for accuracy using a Class 1 sound level meter (SLM). For details of the accuracy check results, see [8], and for the method used for the accuracy check, see [11,12]. The overall noise level and characteristics of the surveyed area and how these changed after the declaration of the state of emergency was lifted were investigated by way of a soundwalk using NoiseCapture.…”

How did "state of emergency" declaration in Japan due to the COVID-19 pandemic affect the acoustic environment in a rather quiet residential area?

“…Thus, a possible effect can be observed and interpreted as the increased traffic volume observed and construction works in this area in May 2020: During the state of emergency, a certain number of people used a car or motorbike for commuting, shopping, and travelling for various purposes, which should have increased traffic volume in this area. For reference, previous survey in the same area (except for the point 6) in August-October 2019 [11] showed that: Instantaneous noise levels (dBA, slow, peak) were 44.8 dBA (minimum, Point 1) to 64.8 dBA (maximum, Point 5). This range roughly corresponds to the above results, which can be inferred that, though the variation due to the day is observed in Table 1, the noise levels fall into the range observed in those observed in usual state.…”

“…This area is occupied by mainly two-storey detached houses, but there is also a somewhat large number of small and large apartments of three to five storeys. In 2019, the noise levels of this area were surveyed as a follow-up to the author's previous study [11], and the results demonstrated that it was rather quiet except for occasional cars passing by. For other data sets in the same area, three sets of geo-referenced sound data taken in August-October 2019 using iPhone XS and three apps (dB Meter Pro, Decibel X and SoundLog) are available in reference [11] in which instantaneous SPL (dBA, slow, peak) taken by dB Meter Pro and Decibel X and LAeq taken by SoundLog.…”

“…After the survey a simple check of the accuracy of measured values by the system used in this work was carried out. Keeping the app and devices in the same setting and condition as was used in the measurement, a simple check was performed according to the following procedures [11]: a pink noise was emitted from a 10 cm full range loudspeaker enclosed in bass-ref cabinet. The noises emitted at various levels were measured by both the Noise Capture on the tablet and a Class 1 SLM (RION, NL-32) simultaneously.…”