AFMG Network Forum

JM · Member

We have EASERA program and was wondering if it could be used to conduct a road tunnel measurement including:
1) Noise
2) RT
3) RaSTI

Traffic noise is expected to 85dBA and road cannot be completely closed for the measurement.

The question would be whether EASERA is capable of gathering accurate/repeatable RT and RaSTI results with the passing traffic. And what our source sound level should be at considering the background noise of 85dBA.

Would greatly appreciate any advice if there are other matters we might need to take note of for this application.

Thank you!

Bruce · Member

Yes, you should be able to gather these measurements.

Note first that EASERA will measure the full STI, not RASTI. That is a better way to do it anyway. See numerous papers from Peter Mapp on that subject.

You will need to have a microphone and preamp that are capable of making measurements in this high level environment without overload. With EASERA the goal is to first measure a "noiseless" STI, then combine it later with the measured Ambient Noise in order to consider Masking and Noise for the actual STI in situ. Do this by using a weighted sweep as the stimulus, and a high number of averages in order to get a noise-free Impulse Response. Then combine this with the noise to get the STI value. You can then also get the RT from this IR if it has adequate S/N (Noise floor more than 10dB below the Txx desired).

JM · Member

Hi Bruce, thank you so much for replying.

It is likely that we try to pick a quieter time for the RT/RaSTI (or STI) test however the tunnel cannot be completely closed from traffic; considering the random traffic noise that will be picked up at the time of measurement (constant or intermittent / vehicle type... etc). I'm not sure if masking is possible unless we are able to simultaneously measure the ambient noise without picking up the impulse...

I gather from your advice taht a high number of measurements is required, and we establish the RT/STI from there.