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In one of the world’s densest cities, peace and quiet are hard to find. As a global hub, Singapore’s skies are always busy, while an extensive web of roads and a well-connected MRT network keep residents constantly on the move. But these conveniences come at a noisy price – the traffic never stops, and for those living nearby, the constant sound is often impossible to escape.
“Singapore’s land scarcity forces housing, schools and workplaces to be built immediately adjacent to expressways, arterial roads, viaducts and busy vehicle corridors,” explained Professor Gan Woon-Seng, who teaches audio engineering at National Technological University (NTU). Additionally, “most residential buildings are high-rise, creating multiple reflection canyons where noise bounces between buildings”.
Moreover, in the city’s hot climate, many residents prefer open-window living, allowing more noise into houses.
To understand how this never-ending noise invades homes, we collaborated with Prof Gan and senior research engineer Santi Peksi from NTU’s Smart Nation Translation Lab. With their help, we recorded sound levels inside 25 residences across the city. All the participants live near a source of steady traffic, such as an airport, a major road or the MRT .
The recordings captured the noise landscape in each home. To make sense of what we found, we first need to talk about decibels.
Decibels are used to measure the intensity of sound. Louder noises correspond to higher decibels. A quiet library is roughly 40dB, while drilling at a construction site is about 76dB. Hear for yourself.
The following clips won’t play at their actual decibel levels; that depends on your device and volume settings. What matters is the relative difference: Listen to how much louder one environment is compared to another.
60dB is 4x louder than 40dB
The tricky thing about decibels is that they increase not linearly, but on a logarithmic scale. That means when noise jumps from 20dB to 40dB, the sound is not twice as loud, but four times as loud. Because of this, little changes in decibels make a big impact.
According to the WHO, excessive noise can cause an array of unwanted health problems – from sleep disturbance and depression to hypertension and adverse birth outcomes – so the organisation has established safe levels of average exposure. For traffic noise, it recommends a daily average of less than 53dB, and less than 45dB for aircraft noise.
Singapore, too, has determined safe levels of noise. The National Environment Agency (NEA) suggests average indoor noise levels should be below 57dB.
“These benchmarks were established by referencing international standards,” said an NEA spokesperson.
The slightly lower WHO level can be tough to achieve in Singapore. “The WHO road traffic noise thresholds are derived largely from European exposure datasets,” Prof Gan explained. “When applied to dense Asian cities, structural, climatic and land-use realities make these thresholds systematically more difficult to achieve, even with strong governance and high-quality infrastructure.”
With the help of Ms Santi, ST analysed up to six hours of recorded noise in each of the 25 homes we visited. A true comparison with WHO and NEA standards would require a full day of recording. Nonetheless, during the hours we visited, the noise in many homes reached levels that, if sustained throughout the day, would exceed both the WHO and NEA safe noise thresholds.
These numbers tell one story. But to really understand what living with excessive noise means, you need to hear it for yourself.
The noise from road traffic and a waterfall can be the same volume, but one sounds peaceful, while the other is intrusive. The difference isn’t in the loudness, but in how our brains interpret the sound.
“Although noise metrics such as decibels provide standardised physical quantification of sound energy, human response to noise is fundamentally subjective,” explained Prof Gan. “Two sounds with identical sound pressure levels can evoke very different perceptions.”
Psychoacoustic researchers have identified several metrics, beyond just volume, that contribute to what makes a noise annoying. Two important ones are sharpness and roughness.
Roughness describes how grating or buzzing a sound feels. It is caused by rapid fluctuations that make a sound harsh or unpleasant. Sharpness, meanwhile, measures how piercing or shrill a sound is.
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