Better measures of turbine noise level needed

I have been reading about the anticipated noise impact of wind farms on the north country. One of the largest problems the public seems to have is understanding the acoustical issues.

Background noise levels are when all the traffic, airline, dogs barking and other intruding temporary extraneous sounds noises are not present. Typical north country background noise levels are in the range of 25dBA to 35dBA and are significantly lower than the noise in towns and cities.

If 55dBA average noise levels from wind turbine farms are permitted to intrude on your property, you will be permitting noise levels that are to be expected in very commercial areas.

All of us are familiar with hearing the whooshing and whistling wind affect the microphones of outdoor weather broadcasts. Unless the low-level background noises are recorded with special microphone wind screens and monitored to verify that wind induced measurement errors are not present the measurements become garbage in, garbage out.

I am a retired acoustical engineer and have spent most of my adult life working for Carrier Air Conditioning in the area of product noise control and after retirement, teaching acoustics at Syracuse University and at RPI.

I have reviewed the environmental impact statements of several local communities that are considering approval of large wind farms in their localities. The only acoustical measurement that I see in their analyses deals with measuring an averaged noise level over the affected area.

These draft environmental impact statements do not evaluate the annoying noises that rapidly change in noise level, such as the cyclic whooshing noises produced when the turbine blades pass by the support pedestal or the transient noises produced at turbine cut-in or cut-out or those periodic noises produced by the turbine gearboxes.

Nor do they document the presence or absence of significant annoyance potential of low-frequency noises or vibrations which are known to be a very significant problem if the noise levels are high enough.

Much of the area affected is located on very shallow limestone shelves which will be directly connected to the massive concrete bases of the wind turbine. This means that the rotor vibrations, blade slap induced vibration on the turbine pedestal and the gearbox vibrations can be telegraphed to houses whose foundations rest on the same slab.

I would hope that the planning boards in our area who are reviewing wind farm noise studies would insist on nothing less than comprehensive, accurate assessments that consider all the possible noise impacts associated with wind turbines.

Charles Ebbing

LaFargeville