A consultant and materials supplier had encountered a complex industrial environmental fan noise problem as multiple rooftop fans were potential noise sources. Whilst on-site, he recorded audio both at the complainant and close to each fan. Unfortunately, it was a very windy day and hence the audio was overloaded most of the time. However, we are able to extract very short samples between wind gusts - as in the sound sample above that also includes the "after the fan noise attenuation" recording during more clement weather...
This enabled us to identify the only fan that matched the frequency of the whine at the complainant - this was a fan that had been previously discounted as a potential problem as it was already fitted with the 2 conventional attenuators visible in the picture.
This analysis (taken from the sound samples above) illustrates that, despite the wind noise, we were able to extract enough information to diagnose which fan was the cause and to devise a solution that permanently eliminated the complaints. This whole process was accomplished within a couple of weeks without a site visit.
