This part of ISO 1996 defines the basic quantities to be used for the description of noise in community
environments and describes basic assessment procedures. It also specifies methods to assess
environmental noise and gives guidance on predicting the potential annoyance response of a community
to long-term exposure from various types of environmental noises. The sound sources can be separate
or in various combinations. Application of the method to predict annoyance response is limited to areas
where people reside and to related long-term land uses.
Community response to noise can vary differently among sound sources that are observed to have
the same acoustic levels. This part of ISO 1996 describes adjustments for sounds that have different
characteristics. The term “rating level” is used to describe physical sound predictions or measurements
to which one or more adjustments have been added. On the basis of these rating levels, the long-term
community response can be estimated.
The sounds are assessed either singly or in combination, allowing for consideration, when deemed
necessary by responsible authorities, of the special characteristics of their impulsiveness, tonality,
and low-frequency content, and for the different characteristics of road-traffic noise, other forms of
transportation noise (such as aircraft noise), and industrial noise.
This part of ISO 1996 does not specify limits for environmental noise.
NOTE 1 In acoustics, several different physical measures describing sound can have their level expressed in
decibels (e.g. sound pressure, maximum sound pressure, and equivalent continuous sound pressure). The levels
corresponding to these physical measures normally will differ for the same sound. This often leads to confusion.
Therefore, it is necessary to specify the underlying physical quantity (e.g. sound pressure level, maximum sound
pressure level, and equivalent continuous sound pressure level).
NOTE 2 In this part of ISO 1996, quantities are expressed as levels in decibels. However, some countries
validly express the underlying physical quantity, such as maximum sound pressure, in pascal or sound exposure
in pascal-squared seconds.
NOTE 3 ISO 1996-2 deals with the determination of sound pressure levels.