Noise levels

[Helinut]

Noise is considered both in terms of absolute noise levels and the dose of noise received. Dose is level x duration of exposure.

A basic threshold for occupational noise levels is 80 dBa exposure on the basis of an 8 hour working day. It does not mean that this cannot be exceeded, but above this there is a risk of hearing loss, if someone was exposed over a long period (i.e. as someone would when working in a factory).

A level of 120 dBa is considered as a threshold at which hearing damage can be caused by a one-off short duration exposure.

Apart from damage to hearing, the other consideration is "noise nuisance". This is what is normally important in "neighbour disputes" like the one you have. It sounds to me like the local authority are trying to set (what they consider) a reasonable level that they can then measure to check for compliance. You don't say where the noise limit is to be measured, which is obviously pretty important.

From your very brief summary, it sounds to me like your neighbours have got hold of some fairly half-baked information about noise and are trying to use it to have their NIMBY way.

In responding to the points raised by your good neighbours:

1. The instantaneous noise level from an R44 will not exceed 120 dBa, even right next to the helicopter. If it did, anyone being near one without hearing protection would suffer hearing damage from a one-off exposure. It will probably exceed 80 dBa, but that is not significant, because the exposure time will be short (usually). Unless, of course you are the pilot and you don't wear a headset!!
2. The occupational requirement to consider hearing protection above 80 dBa is only when the exposure period approaches an 8 hour working day - It is not relevant to your situation because the exposure period from your operation will be short.

The number of take-offs and landings is not significant, in terms of the limit imposed by the LA, assuming that you don't squeeze all of them into a 15 minute period! As long as you separate each movement so that only one occurs in a 15 minute period, you only need to be able to show that the average noise level over any 15 minute period is less than 55 dBa. If you take a typical start-up and take-off, the noise levels would need to be measured from say engine start, warm-up, pre-flight checks, take-off and then departure through to the aircraft disappearing.

You can ease matters by keeping it as prompt as possible.

An approach and landing would be the same but in reverse. However, you would expect that to be quicker and less noisy.

There are meters that measure both the instantaneous and the dose/average levels over a period.

The best way to PROVE what is going on is to measure it with meters. It sounds like the LA might be wanting to do that anyway.


Hope that helps a bit. If you want you can PM me and discuss it some more..