Limited subjective assessments of synthesized turbine infrasound and low frequency sound comprising frequencies 0.8 to 53 Hz suggest that near-threshold audible cues play a primary role in perception. Infrasound pulses recorded in field environments exhibit peak pressures on the order 0.1 to 0.2 Pa (74 – 80 dB peak SPL) at 400 meters, the approximate minimum setback allowed by any known noise guideline for wind farms. Review of recent field measurements taken at 1,100 meters from a small array of industrial turbines under very steady conditions show peak infrasound amplitudes of approximately 0.04 Pa (66 dB peak SPL) and evidence of blade-pass frequency periodic short bursts of tonal energy just above normal threshold in the frequency range 25-53 Hz. Syntheses of infrasound pulses accompanied by these tone bursts produce adverse subjective reaction with or without the infrasound pulses present and no reaction if the tone burst peak pressure is below threshold. The work described here tests the response of two test subjects to synthesized test signals of five-minutes duration. It is possible that longer term exposure could result in some test subjects becoming either more sensitized or acclimated to the noise, resulting in different responses to those described in this paper.
|Publication status||Published - Apr 2015|
|Event||6th International Conference on Wind Turbine Noise - Glasgow, United Kingdom|
Duration: 20 Apr 2015 → 23 Apr 2015
|Conference||6th International Conference on Wind Turbine Noise|
|Period||20/04/15 → 23/04/15|