Type 1 (class 1) sound level meter. This is a hand-held or tripod-mounted device to display and record instantaneous and/or short duration surveys. They will also integrate sound level readings (Leq) over a time period from 10 seconds to 200 hrs. Commonly perform Octave analysis to determine from which frequency bands the noise is detected. Results are stored to SD card and downloaded to Excel for reporting and analysis.
A portable logger worn by a worker (subject), pinned or clipped to their shoulder. The dose meter records sound levels (dB) against criteria established at the outset, as appropriate for the particular application. Results are stored internally, downloaded to a PC and automatically compiled into reports. Ideal model for OH&S surveys.
For often prolonged exposure to the elements, environmental loggers are built to be rugged and self contained. Housed in a weatherproof Pelican case and powered by one (or two) 12V batteries, supplied with locks and chains they can be left in the wild for up to a month, all the while recording data every 100ms. Common applications include baseline and post installation surveys of wind farms, traffic noise surveys, construction zone monitoring. Data is stored to USB flashdrives which are hot-swappable, allowing replacement without interruption to data collection.
While Excel can perform much of this analysis on small amounts of data, the sheer amount of data collected from an environmental survey makes this a daunting task. Firefly software enables analysis of split files and from SPL-A, SPL-A, LeqA, LeqC and .wav files, produce any number of time weighted Leq statistics, Ln indices, octave and 1/3 octave statistics, and may replay any portion of .wav files.
Glossary of terms
SPL – Sound Pressure Level, the basic measure of noise level, expressed in decibels.
Sound Level – Sound Pressure Level with a Frequency weighting, such as dB(A).
Integrating Averaging Sound Level Meter – A Sound Level Meter which accumulates the total sound energy over a measurement period and calculates an average.
Acoustic Calibrator – An instrument that provides a reference noise source that is used to calibrate and check the performance of a Sound Level Meter.
Type 1 – Laboratory & Field Grade for Sound Level Meters.
Type 2 – General Field Grade for Sound Level Meter.
A Weighting – dB(A) A-weighted noise measurements approximate to how the human ear perceives noise.
C Weighting – dB(C) Standard frequency weighting for sound level meters, commonly used for higher level measurements and Peak Sound Pressure levels
Peak – The maximum value reached by the sound pressure at any instant during a measurement period (in dB usually with C frequency weighting).
1:1 Octave Band Filters – A division of the frequency range into bands, the upper frequency limit of each band being twice the lower frequency limit.
1:3 Octave Band Filters – Single 1:1 Octave bands divided into three parts.
LA10 – The noise level exceeded for 10% of the measurement period with 'A' frequency weighting calculated by statistical analysis.
LA90 – The noise level exceeded for 90% of the measurement period with 'A' frequency weighting calculated by statistical analysis.
LAE – Sound Exposure Level (SEL) with 'A' frequency weighting.
LCE – Sound Exposure Level (SEL) with 'C' frequency weighting.
LCPEAK – Peak Sound pressure level with 'C' frequency weighting.
LEQ – Equivalent continuous sound pressure level. A measure of the average sound pressure level during a period of time, t, in dB.
LN – Statistical analysis of noise levels. The n denotes the percentage exceedence.
% Dose – The noise exposure expressed as a percentage (%) of a fixed level for 8 hours.