Guidance on the Control of Odour and Noise from ... - Defra

Table 2.4 Results of CIEH survey of noise complaints attributed to
commercial/leisure activities in England and Wales (CIEH, 2003 [6] ).
Category of noise nuisance Commercial/leisure
Complaints received 40,602
Complaints per million population 1,014
Sources complained of 32,302
Sources confirmed as a nuisance 4,771
Nuisances remedied without notices being served 3,140
Notices served 1,310
Prosecutions 95
Convictions 48
Nuisances remedied by Local Authority in default 125
2.2.2 Properties of noise
Noise is any unwanted, unpleasant or harmful sound created by human activities.
Different people perceive it in different ways. Human hearing detects frequencies
from 20Hz to 20kHz with sound pressure levels ranging typically from 0 dB (normal
threshold of hearing) up to 140 dB (i.e. near a military aircraft taking off).
Sound arises as a result of the vibration-excitation of an elastic medium and resultant
propagation of energy through the medium in the form of waves. It results in the
excitation of the eardrum, and hence its perception. The sound waves in the medium
can propagate several shapes including spherical and cylindrical forms depending on
the nature of the source.
Frequency content: Noise is considered tonal if there only one frequency is
predominant in the spectrum (and its harmonics) or broadband, where there is a
contribution over many frequencies.
Decibels and levels: The response of the human being to sound is approximately
proportional to the logarithm of energy. Therefore a change of energy from 2-8 units
is perceived as being similar to a change from 8-32 units. To represent this
proportional characteristic decibels are used. As the energy levels are proportional to
the pressure it is usually represented in relation to a reference pressure level in the
following form:
= 20 log
SPL 10
Where
⎛
⎜
p
⎜
⎝ pref
⎞
⎟
⎠
−5
pref = 2 × 10 Pa.
To add decibels (e.g. Levels L1 and L2) the following equation is used:
20