Perception of noise varies from person to person. Even the ticking of a wristwatch (20 dB) can split opinion. In general, sound at a level of 40 to 65 dB is perceived as quiet, normal and pleasant. For us, loud would mean from around 80 dB. Scientists refer to sound above this threshold as ‘loud’ or ‘noise’. In the case of a television set at normal volume (70 dB), this limit has not yet been exceeded, while a passing lorry (90 dB) or a car horn (110 dB) are well above it. And in the case of a jackhammer (120 dB) or a fighter jet (130 dB), the only thing to do is close your ears or reach for your earplugs. Road traffic is the largest source of noise, followed by aircraft noise and noise in the workplace. Around 15 to 20 per cent of the population are considered to be hearing-impaired, and this is increasingly affecting young people. However, this is just one of the conditions caused by noise.