Sound Levels

Decibels (dB) are most commonly used as a measure of sound level, but they are also used in electronics, signals and communications.

Sound is a variation in pressure detectable by the ear, whereas noise is undesired sound, or any sound which causes disturbance or annoyance to the recipient. The unit used to describe sound wave intensity is the bel, named after the inventor Alexander Graham Bell. The human ear is sensitive enough to detect changes of as little as 1/10 of a bel, and so sound intensity levels are described in decibels.

A sound wave’s intensity is the average amount of energy transmitted per unit time through a unit area in a specified direction. The sound intensity level, I, in decibels is 10 times the logarithm of the ratio of the intensity of a sound wave to a reference intensity.

Noise Disturbance

Building acoustics can help to mitigate the effects of noise disturbance which can have negative effects on health, well-being and general quality of life.

The Noise Policy Statement for England (NPSE) defines noise pollution as:

- Environmental noise: which includes noise from transportation sources. - Neighbour noise: which includes noise from inside and outside buildings. - Neighbourhood noise: which includes noise arising from industrial and entertainment premises, trade and businesses, construction sites and noise in the street.

This can be an important consideration for the location, design and construction of new developments.

Point of Reference

Points of Reference *measured in dBA or decibels:

• 0 The softest sound a person can hear with normal hearing
• 10 normal breathing
• 20 whispering at 5 feet
• 30 soft whisper
• 50 rainfall
• 60 normal conversation
• 110 shouting in ear
• 120 thunder