The COVID-19 pandemic caused lockdown in many countries. Acousticians made surveys to monitor how cities became quieter under the lockdown, mainly in the central areas of cities. However, there have been few studies on changes in the acoustic environment due to the pandemic in rather quieter residential areas. It may be expected to be different from the effect in originally noisy areas. Also, the effect could be different in Japan, because the "state of emergency" declaration there was different to lockdown. Considering these circumstances, this paper reports the results of noise monitoring and makes some observations on the acoustic environment in residential areas remote from city centres, to provide an example of how the acoustic environment was affected by the "state of emergency" declaration due to the COVID-19 pandemic in Japan. The results showed that the reduction of noise levels was somewhat smaller than that reported in large cities. Also, comparing the results after the cancellation of the "state of emergency", the noise level increased again. However, observations of noise sources imply that a possible change in human behaviour may have also affected the acoustic environment.
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY) 4.0 https://creativecommons.org/licenses/by/4.0/, which permits unrestricted use, distribution and reproduction in any medium, provided the original author and source are credited.
Dear Dr Almagro
Many thanks for your constructive comments on this version of the preprint. I have already submitted a revised version which is soon posted here.
I do understand your concerns on the accuracy, particularly at low levels. Since I could not bring out the Ckass 1 SLM from our lab, I did not have any other choice but a mobile devices.
The accuracy of the SLM apps on the devices depends on (1) the device (in many cases, so called noise floor or internal noise); (2) App's design. When the same app is used, the accuracy depends on the device; on the contrary if the device is the same different apps can show different accuracy. (Please see ref 11)
Regarding NoiseCapture, I also checked its measured value with that measured by SLA app on iPhome XS and obtained fairly good agreement. Also, by using the device and app used in this submission I had checked that noise levels around 35 dBA could be obtained. Considering that the measured results in this survey are all greater than 39dBA ca, at least, the relative difference which is required for qualitative discussions, which was rather important in this work, may be obtained even by these methods.
As mentioned above, even though the device is the same, the accuracy may vary with apps. Considering this fact, I shall add some data on the accuracy to address your comments. Please wait for a while until I can have a professional SLM at hand: I will make a further revision.
Once again, many thanks for your thoughtful comments, I appreciate it very much.
Kind regards
Kimihiro Sakagami