Femke B. Gelderblom

How to measure community tolerance levels for noise

Relationships between noise exposure and transportation noise induced annoyance have been studied extensively for several decades. The annoyance due to aircraft noise exposure is in the present paper assumed to be influenced by the day-night yearly average sound level (DNL). It has long been recognized that the annoyance also depends on non-DNL factors, but this is complicated-resulting in a variety of different modeling strategies. Motivated by this, the community tolerance level (CTL) was introduced in 2011 for a loudness-based psychometric function. It is a single parameter that accounts for the aggregate influence of other factors. This paper suggests and investigates different methods for the measurement of the CTL. The methods are illustrated on data found in the literature, on recent surveys around two Norwegian airports, and on simulated data. The results from the presented methods differ significantly. An elementary method is shown to give a measurement of the CTL with smaller uncertainty, and is recommended as a replacement for the originally suggested least-squares method. Methods for evaluating the measurement uncertainty are also presented.

CTL—A useful tool for inter-survey comparisons

The concept of Community Tolerance Level was presented in 2011 and in subsequent analyses the CTL has proven to be a useful tool for comparing results from different surveys on noise annoyance. The CTL provides a robust single-number description of the prevalence of annoyance in a community noise survey. It has been shown that accurate predictions of the prevalence of highly annoyed residents can be achieved by relatively few survey interviews as the selection of respondents does not have to cover the whole range of exposure. A re-analysis of existing studies on aircraft noise annoyance has shown that there has been virtually no change in peoples response to this type of noise over the past 50 years, but there is a distinct difference in the response depending on the rate of which the noise situation has been changing. A similar analysis of results on road traffic noise from surveys conducted over a period of more than 50 years, will be presented.

Sound exposure during outdoor music festivals

Most countries have guidelines to regulate sound exposure at concerts and music festivals. These guidelines limit the allowed sound pressure levels and the concert/festival’s duration. In Norway, where there is such a guideline, it is up to the local authorities to impose the regulations. The need to prevent hearing-loss among festival participants is self-explanatory, but knowledge of the actual dose received by visitors is extremely scarce. This study looks at two Norwegian music festivals where only one was regulated by the Norwegian guideline for concert and music festivals. At each festival the sound exposure of four participants was monitored with noise dose meters. This study compared the exposures experienced at the two festivals, and tested them against the Norwegian guideline and the World Health Organization’s recommendations. Sound levels during the concerts were higher at the festival not regulated by any guideline, and levels there exceeded both the national and the Worlds Health Organization’s recommendations. The results also show that front-of-house measurements reliably predict participant exposure.