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Tuesday, July 9 • 15:30 - 15:50
UNCERTAINTY ANALYSIS OF ENVIRONMENTAL SOUND: A STATISTICAL ANALYSIS OF 100 SITES WITH MEASUREMENT OVER SEVERAL DAYS.

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In the course of environmental monitoring, instruments are sometimes left at secure locations for more than 24 hours. We have identified approximately 100 sites where road traffic is dominant, with two or more days' worth of data. The sites have an average of four entries (range 2 – 12 days), with about two-thirds sampled on weekdays and the remainder at weekends. Each entry will typically have 288 5-minute samples covering a 24-hour period, comprising equivalent sound pressure levels, together with corresponding percentile data. Such data allow us to examine the variation between 16h (day) 8h (night) and 24h means. In examining these historical data it is clear that the simple arithmetic mean of a 24-hour sample and its standard deviation are very useful indicators of a site's stability. For example, where an arithmetic mean has a low s.d. (measured over 16 or 24 hours) it simply indicates that the data do not fluctuate much, and therefore the 'equalised' or Log average mean will be quite close to the arithmetic mean. A higher s.d. tends to indicate a 'spiky' response, which results in a separation of arithmetic and log averaged means because of the weighting afforded to larger values. In this paper we show that statistical analysis of variance provides a useful general estimate of uncertainty, as it is estimated over replicated mean records at multiple sites. Differentiating between weekdays and weekends gives a lower uncertainty value for weekdays with an overall uncertainty of c. ± 1.5 dB(A).

Moderators
LH

Lars Håkansson

professor, Linnaeus University

Authors

Tuesday July 9, 2019 15:30 - 15:50 EDT
Westmount 2
  T01 Ac. meas. & instrum., RS03 Measur uncert in acoust