Noise Mapp. 2021; 8:236–248 Research Article Huey Ting Diong*, Richard Neitzel, and William Hal Martin Spatial evaluation of environmental noise with the use of participatory sensing system in Singapore https://doi.org/10.1515/noise-2021-0019 Received Apr 05, 2021; accepted Jun 14, 2021 List of abbreviations Abstract: Existing studies in Singapore on environmen- LAeq,24h Equivalent continuous 24-hour average sound tal noise are scarce and limited in scale due to the need level for expensive equipment and sophisticated modelling ex- LAeq,30sec Equivalent continuous 30-second average pertise. This study presents the approach of using partic- sound exposure ipatory sensing and mobile phones to monitor environ- Lden Day-evening-night level. It is the equivalent mental sound levels around Singapore. iPhones running continuous average noise exposure over a the AmbiCiti application was adopted to sample equiva- day, with penalty of 5dB and 10dB applied lent continuous 30-second average outdoor sound levels to evening (19:00 – 23:00) and night-time (LAeq,30sec). The aggregated mean of each region was eval- (23:00 – 07:00) noise respectively uated and the spatial distribution of environmental noise CBD Central business district was analysed using noise maps generated from the mea- dBA A-weighted decibels surement data. A total of 18,768 LAeq,30sec measurements GIS Geographic information systems were collected over ten weeks. About 93.6% of the daytime IDW Inverse distance weighted interpolation measurements (07:00 – 19:00) exceeded the WHO recom- WHO World Health Organisation mended level of 55 dBA to minimise negative non-auditory health effects due to noise. The results of this study sug- gest that the population of Singapore is potentially at risk of adverse non-auditory health effects and, to a lesser ex- 1 Introduction tent, hearing loss due to community noise levels. How- ever, the measurements exceeding 70 dBA were frequent Environmental noise is an issue commonly faced by the enough to warrant concern about contributions to the cu- denizens of urbanised and urbanising areas worldwide. It mulative lifetime sound exposure contributing to hearing is defined as noise generated from all sources, excluding loss. The work also demonstrates that sound maps of an sources of occupational noise exposure in workplaces [1]. area can be efficiently generated using calibrated applica- Studies in many large cities over several continents have tions running on smart phones. reported their populations are exposed to high level of en- Keywords: environmental noise, noise exposure, partici- vironmental noise with traffic and transportation noise as patory sensing, noise mapping main contributors [2–5]. There is growing evidence regarding the negative im- pact of noise on health. Non-auditory effects of noise like cardiovascular and metabolic effects [6, 7], sleep distur- bance and interference [8], cognitive impairment [9, 23], annoyance [10] and mental health impacts [11, 12] have been described. Lifelong exposure to sound level of more *Corresponding Author: Huey Ting Diong: Department of Oto- than 70 A-weighted decibels (dBA) equivalent continuous laryngology, National University of Singapore, Singapore; Ng Teng 24-hour average sound level (LAeq,24h) increases the risk Fong General Hospital, Singapore, of noise-induced hearing loss, especially for vulnerable E-mail: [email protected] groups with increased susceptibility to the harmful effects Richard Neitzel: Department of Environmental Health Sciences, of noise [13]. University of Michigan, Michigan, USA, E-mail: [email protected] William Hal Martin: Department of Otolaryngology, National Uni- An evaluation by the World Health Organisation versity of Singapore, Singapore, E-mail: [email protected] (WHO) on the burden of disease due to environmen- Open Access. © 2021 Diong et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution 4.0 License Spatial evaluation of environmental noise Ë 237 tal noise concluded that at least one million disability- 3. To facilitate urban planning, especially in land- adjusted life years were lost annually in western Europe scarce countries like Singapore. due to the undesirable health impacts caused by traffic re- 4. To improve public knowledge and awareness, and to lated noise. A major part of the burden was contributed shape opinion about noise pollution. by sleep disturbance and annoyance, which accounts for There is growing interest in the use of participatory 903,000 years and 654,000 years respectively [14]. This sensing for monitoring environmental noise levels due to level of burden places environmental noise as the second the relatively low cost and increasing worldwide pene- most pressing environmental issue after air pollution. Sig- tration of smartphones capable of measuring sound lev- nificant economic savings and gains with the reduction of els [20–22, 24–26]. This strategy is based on a person- environmental noise by 5 dB have been reported in one re- centric collection of environmental data. NoiseSPY, Ear- cent study [15]. The negative health effects due to environ- Phone and NoiseTube were the first few functional out- mental noise have prompted WHO to introduce guidelines door environmental noise sensing systems relying on mo- on the recommended sound levels to mitigate effects due bile phones to facilitate mass participation environmen- to environmental noise [1, 14, 16]. tal monitoring and assist in environmental data collection Studies in Singapore on environmental noise are on a large scale [25, 27, 28]. Multiple short sound mea- scarce, limited in scale, and have focused mainly on traf- surements were recorded by volunteers with their smart fic noise in the daytime and evening time [17, 18].Sy et al. phones at different locations. Other data captured by these conducted a two-phase study, conducting 10-minute mea- sensing systems includes username, journey ID, the last surements from 16:00 to 19:00 at over 300 sites in the first valid GPS location and time collection. Studies have been phase and 3-minute measurements at fixed half-hourly in- carried out on the accuracy of smartphone sound sensors tervals at 20 selected sites from 09:00 to 19:00 [17]. Bhanap for noise study. When properly calibrated, these smart- did continuous sampling at 1-minute intervals from 08:30 phone sound sensors could achieve performance similar to 22:00. The reported sound levels from traffic from these to professional sound level meters [20]. However, the accu- studies ranged from 60 to 74 dBA depending on the traffic racy of measurements is affected by factors like the types conditions [18]. of phones (iOS/ Android), the condition of the phones, To investigate the impact of localised community the way the users carry their phones and the geographical noise in high-rise residential environments, Alam, Eang, topology and meteorological factors (altitude, vibration, Tan, & Tiong conducted sound level measurements at wind, air pressure, etc.) [20, 29–31]. Comparison with offi- 10-minute intervals at building façades and investigated cial simulated noise maps is challenging due to the differ- upward noise propagation from five identified sources ence in approach and data representation. However, noise of community noise. They also interviewed residents maps generated from these data have generally shown from five residential estates that included food centres, similar overall sound level distribution when compared children’s playgrounds, soccer fields, basketball courts, to official simulated noise map [20]. More recent partici- and waste disposal trucks to investigate their subjective patory sensing initiatives have included soundscape sens- responses to community noise. The measured daytime ing, which investigated the subjective assessment of sound LAeq h from different scenarios near ground level ranged ,16 levels, sound comfort levels and sound harmoniousness between 51 and 79 dBA, with increases in elevation lead- levels. The inclusion of a large network of participants in ing to reduced LAeq h values. The study also found that ,16 data collection enhanced data collection efficiency and en- 78% of the respondents felt slightly, quite, or very dis- abled accumulation of large data sets for soundscape re- turbed by these community noises, with a significant pro- search, design and planning [32, 33]. portion (33%) of the respondents experiencing sleep dis- The present study utilized participatory sensing and turbance [19]. mobile phones to measure outdoor environmental sound Extensive sound mapping has been challenging due to levels in Singapore. The study also compared measured the need for expensive equipment and sophisticated mod- sound levels to recommended guidelines for environmen- elling expertise. The need for extensive data on local out- tal noise and assessed the associated potential risk of door noise conditions persists for several reasons: negative non-auditory and auditory effects. Through the 1. To monitor the levels of environmental noise around utilization of geographic information systems (GIS), this the country so as to set a reference for policy makers. study provided an overview of general trend of the spa- 2. To enable the development and enforcement of poli- tial sound distribution and local variations in sound levels cies for local noise regulation. across Singapore. 238 Ë Diong et al. Figure 1: Demarcated regions of Singapore 2 Methodology orative effort of mainly French and other European