ABSTRACT: In measuring the environmental noise level for such purposes as compliance monitoring and nuisance noise assess- ment, the most often used statistic is the A-weighted sound pressure level (SPL), often reported as a percent ex- ceedance level (e.g. L10 or L90) averaged over a time interval such as 10 minutes or 24 hours. This statistic can not be relied upon in situations where noise has ‘special audible characteristics,’ such as modulation or tonality, since increases in the sound pressure level (SPL) of the loudest n% of sound will be ignored. Furthermore, the use of A- weighting underestimates the lower-frequency sounds, which have recently been shown to be perceived by humans through alternative mechanisms, therefore different measures are required. The analysis of large amounts of data for compliance monitoring can be a time-consuming process. Errors can occur due to inappropriate analysis methods or flawed understanding of the noise under investigation. This paper reports on: (1) some of the current issues with us- ing the A-weighting and exceedance statistics as measures of loudness; (2) the development of several alternative measures to analyse environmental sounds from various sources that exhibit ‘special audible characteristics’ (includ- ing wind farms and impulsive noise); (3) the requirements of automated, standardised methods of data reporting, analysis and assessment for large and complex data sets and (4) the development of a new sound measurement tool that implements the proposed analysis techniques while extending the acoustic spectrum down to less than 1 Hz: the Spectro-Acoustic Meter (SAM).
School of Engineering and Advanced Technology, Massey University, Palmerston North, New Zealand
Atkinson and Rapley Consulting, Palmerston North, New Zealand
Elliott Sound Products, Thornleigh, Australia
Presented at the annual convention of the Australian Acoustics Society, 2nd-4th November 2011, Queensland, Australia
Download original document: “Environmental Noise: Better Measures and Reporting Needed”
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