Definitions

• Noise is sound that’s unwanted by, or distracting to, the person receiving it.
• Decibels (dB) are a way to measure how loud a sound is, and we refer to them throughout this proposal. They accurately reflect how the human ear hears sound and help us talk about a wide range of sound levels, from very quiet to very loud, using numbers that are easier to manage. An increase of 10 dB means a sound seems roughly twice as loud to someone.
• An average measurement of decibels (LAeq) means that, instead of taking the noise measurement in one moment, the noise is measured over a time period, usually 15 minutes, and then averaged. This method is designed to better capture how we hear noise, allowing for changes in volume to be taken into account, such as the quiet moments between banging noises or the clanging of metalwork, or the way music tone and volume changes during a song.

Where we measure

Noise is measured at the boundary of the site receiving the noise. This is to best reflect how a person is experiencing the noise at their specific location. It also means that noise received at a home in a residential zone is measured against, and needs to comply with, the noise limits for that zone. Noise from a bar in a commercial zone, received by someone living in a residential zone, also needs to comply with the noise limits for the residential zone.

Decibels in the real world

The table below lists different kinds of noises we might experience day to day and their approximate measurements in decibels.

Environmental noise
Whisper in a library	30 dB
Normal conversation at 1 to 1.5 metres	60 to 70 dB
Phone dial tone	80 dB
City traffic (from inside a car)	85 dB
Level at which long-term exposure may result in hearing loss	90 to 95 dB
Riding a motorcycle	100 dB
Lawnmower at 1 metre	107 dB
Loud rock concert (measured inside a venue for an indoor concert)	115 dB
Pain can be experienced	125 dB
Level at which short-term exposure can cause permanent hearing damage (e.g. a gunshot)	140 dB

Noise in the central city

As a rule of thumb, the central city is louder than the suburbs. Many types of noise are present in the central city, including people and crowds, construction and traffic, rubbish collection, music in homes and at venues, and retail and industrial noise like extractor fans. These types of noise add up to form the background noise that isn’t attached to any one particular place or activity. In the central city, this background noise doesn’t generally fall below 50dB L_Aeq and is often 60dB L_Aeq or above during both the daytime and night-time.

More information about central-city noise, including noise-smart living and managing noise as a business, is available on our Sound in the Central City webpage.