Practical observations on evaluating frost fan noise

Thanks for having me back on the blog again Jack.

This has obviously been a busy time for frost fan users and people concerned with their noise. I had previously posted a description of a method for evaluating the noise from a frost fan by measuring its rotation and a reason that this is necessary. This is a follow up to that description to describe the practical aspects of the measurement system.

The recent frost events (6^th,7^th,11^th of October 2009) provided an opportunity to evaluate the method for testing frost fans for compliance with Council regulations.

The evaluation was very useful in that it highlighted some improvements, limitations and successes of the method. It also threw up an unexpected piece of data that will be relatively important in evaluating the current noise environment and potential improvements.

The testing has confirmed that the measurement of fan rotation at night is possible and practical. It can easily be carried out at a distance of over 200m, depending on the type of fan (the dark green of the typical Amarillo means that the practical recording distance of these machines is reduced).

Recording using infrared is possible at 100m, but unless there is a specialist requirement for it, visible light gives an easier result to work with.

Noting the direction that the fan is facing is important, and often it is easier to note that verbally when recording as a note for later analysis.

The use of GPS to track location is very useful when recording in some remoter areas when familiar geographic references are absent.

It was found that in spite of the success of recording fans at night, it was remarkably easy to record a large number of fans just before and after sunrise as the ‘nightshot’ capabilities of some cameras provide suitable illumination for recording.

As the results of the evaluation have the potential to cause a certain amount of interest from more that one side of the frost fan noise debate, they will be posted separately at the time that the Council is informed of the issue via the complaint process.

Regards Malcolm