Measurement Method

The Sound Pressure Level (SPL) was measured with a Rion Sound Level Meter (SLM), using a statistical pass-by method. The measurements were made using A-weighting characteristic.

Microphone location was compliant with recommendations in Australian Standard AS2702:-

• Microphone height: 1.2m ±0.05 m above the ground surface
• Horizontal distance ofvehicles from microphone:
  The microphone was 6 m from the edge of the nearest lane on which vehicles were travelling.

For this investigation, the focus is to compare performance of different asphalt types, so the SPL produced as a single vehicle passed the microphone was measured and recorded. It was not necessary or relevant to undertake time-based statistical SPL measurements [e.g. Leq, L10(18hr), etc].

The SPL’s of both northbound and southbound vehicles were recorded, the results averaged and compared between Test Point sites. Only single-vehicle-passes were measured (i.e. if there was both a northbound and a southbound vehicle passing the measurement point at the same time, or more than one vehicle passing-by in either direction, these measurements were ignored. Again, this was done to ensure valid comparative results between sites).

Vehicle speed at each test site was substantially the same.

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© 2008

Above: Sound Level Meter