Why are some sounds more annoying than others?
Decibels (dB) are a well-known measurement that can tell us about the intensity – or volume – of a sound. But the impact of this noise can’t be measured in dB alone. For example, during the COVID-19 lockdown in spring 2020, London’s roads were almost clear of traffic, and overall noise levels dropped significantly. Yet complaints about noise rose significantly in the same period. This means we need to consider the overall sound environment, says Jian Kang from University College London. “Our study(opens in new window) in urban open public spaces indicated that when the sound level is higher than 65-70 dB, the higher the decibel level is, the less comfortable people feel,” Kang explains. “But below this level, other factors play an important role.” Kang and his colleagues interviewed over 9 000 people in 14 public city spaces across Europe to assess how annoyed they got by certain sounds. They found cultural background, age, gender, education level, residential status and even a person’s behaviour when perceiving a sound all affect annoyance levels. Subjective evaluations of sound levels even differ between cities(opens in new window), potentially reflecting cultural differences. “On the acoustic side, in addition to dB, the frequency characteristics, including tonal side, and time domain variation, also play important roles,” Kang adds. Both the source and the meaning of a sound play a role. While almost half found hearing music played on the street favourable, only 4 % enjoyed it coming from passing cars. And if a baby is crying, annoyance levels can vary depending on whose baby it is, Kang says. In the SSID project, which was funded by the European Research Council(opens in new window), Kang and his colleagues from multiple scientific fields worked to measure the impact of sounds on human comfort. The work involved defining descriptors, indicators and indices for soundscapes, which will help policymakers and other interested parties more easily access the information. Intriguingly, increasing noise levels can lower acoustic discomfort. Introducing a pleasant sound such as running water also seemed to improve people’s experience(opens in new window), even if the resulting general sound levels were higher. Such findings could help with the design of urban spaces, to reduce the adverse health effects(opens in new window) associated with unwanted environmental noise such as traffic or construction – and perhaps make cities a little less annoying to live in. Click here to find out more about Jian Kang’s research: Measuring how humans experience acoustic environments