Box 10G Measuring noise in the urban environment

The decibel scale of sound measurement is logarithmic and ranges from 0 (the threshold of normal human audibility) to 130 (the threshold of pain). A 10 dB increase in acoustic power corresponds to an approximate twofold increase in apparent loudness. The A-weighted sound level, indicated with dB(A), is the sound level approximating the frequency sensitivity of the human ear.

One method of measuring sound quality uses a quantitative descriptor, the background noise level. In addition, Leq measures the average of different noise intensities over a defined period of time. The second method is based on a qualitative descriptor of the landuse designation of a specific area. While the use of a quantitative descriptor which can be objectively measured is preferable, it is not always practicable and is often substituted by a qualitative evaluation. Table 10.8 describes two assessment criteria in a sequence of degrading acoustic quality ranging from nature conservation areas to industrial areas.

For further details on the measurement of noise see Box 16B.

Source: von Meier, 1993


Table 10.8 - Two methods of assessing the acoustic environment

Source: A von Meier, 1993, and K M Müller (CEC DGXI)

  Quantitative methodQualitative method:
landuse designation
Acoustical quality
Typical noise levels
L95/dB(A) Leq/dB(A)
day 25 35 Areas designated for
nature conservation
Only natural sounds being heard,
like rustling of leaves
night 25 35
day 40 50 Areas designated for hospitals,
sanatoria, homes for the aged,
'soft' recreation
Very quiet rural environment
night 30 40
day 45 55 Purely residential areas Quiet suburban neighbourhood
night 30 40
day 55 65 Mixed residential areas with
some light industry and
civic centres
Typical urban noise situation
night 40 50
day 65 75 Predominantly industrial areas Very noisy, unfit for permanent
human habitation
night 65 75