Results form noise surveys around airports demonstrate a large spread in annoyance response data. The noise dose such as L_(eq), L_(DEN), etc., is typically used as the acoustic indicator, and the large spread is often attributed to "non-acoustical factors", or more accurately "non-dose factors" (non-DENL factors). The CTL-method uses a pre-defined dose-response function (the duration-adjusted loudness function) and expresses the annoyance response differences between airport communities in terms of the Community Tolerance Level. The CTL value, in decibels, is an indicator that combines all other non-dose factors in a single number. In a noise survey the respondents are typically asked to assess the annoyance on a scale with pre-defined end points. The scale can either be numerical, e.g. "0 - 10" or it can consist of categories with verbal labels such as "not annoyed", "moderately annoyed", etc. For data analysis purposes the responses are usually transformed into a quantity annoyance score, AS. The annoyance score denotes the magnitude of annoyance on a scale "0 - 100". In this paper we will show that the functions describing the annoyance caused by aircraft noise, either in terms of the annoyance score, AS, or in terms of the community tolerance level, CTL are non-airport specific, and the response differences between different airports or airport communities can be expressed by a single number.
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