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Sound Intensity
Sound intensity is measured in Decibels (dB). This is a logarithmic scale in which an increase of 10 dB gives an apparent doubling of loudness.
Sound pitch is measured in Hertz (Hz), the standard unit for the measurement for frequency. The audible range of sound for humans is typically from 20 Hz to 20,000 Hz, although, through ageing and exposure to loud sounds the upper limit will generally decrease.
Environmental Noise Levels
According to the National Institute for Occupational Safety and Health, the maximum exposure time at 85 dBA is eight hours.
At 110 dBA, the maximum exposure time is one minute and 29 seconds. If you must be exposed to noise, it is recommended that you limit the exposure time and/or wear hearing protection.
A three dBA increase doubles the amount of noise, and halves the recommended amount of exposure time.
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.
Sound Insulation
Two parameters are used to describe the sound insulation of a partition, Dw and Rw. Dw represents the sound insulation between rooms on-site. Since these figures describe the fnal site requirements, Dw levels are specified by clients and Building Regulations. Rw represents the lab tested sound insulation of an element making up a partition wall/floor type. Due to flanking and other factors, lab rated sound reduction levels will not be achieved on-site. Conventionally, there is a 5 to 10 dB reduction between a Rw lab tested figure and an on-site Dw figure. The conversion between Dw and Rw is relatively complex and takes into consideration receiver room volume, receiver room reverberation times and the area of the separating partition. The conversion between Rw and Dw should always be calculated.
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