Effects of wind farm noise characteristics on subjective human responses

Author: Mahmoud Ahmed Alamir

Alamir, Mahmoud Ahmed, 2022 Effects of wind farm noise characteristics on subjective human responses, Flinders University, College of Science and Engineering

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Wind energy is a clean, economically viable and environmentally friendly renewable energy source. However, questions have been raised concerning potential adverse health effects of wind farm noise (WFN). This thesis sought to determine the extent to which subjective responses to WFN are judged differently from road traffic noise (RTN) responses. It also investigated whether WFN characteristics such as tonal and broadband amplitude modulation (i.e., WFN level variability) and masking background noise (i.e., noise added to WFN), including long- and short-range RTN, pink noise and room criteria curve noise, affect sleep acceptability threshold levels (SATs). Relative SATs to a baseline stimulus representing the general spectrum of WFN for tonal and broadband amplitude-modulated (AM) WFN were also presented. This study included groups of participants of different ages and localities. Each group also had different self-reported noise sensitivity, allowing, for the first time, a comparison between group responses to WFN through listening tests. Participant groups were WFN-sensitive, WFN-insensitive, quiet rural area and RTN-sensitive participants defined on the basis of residential location and self-reported sensitivity to WFN or RTN.

WFN and RTN with different characteristics, including tonal AM WFN, were presented at six levels to examine dose-response relationships with annoyance, loudness and potential to disturb sleep. WFN with tonal amplitude modulation was perceived as more annoying and yet less loud than RTN.

Tonal AM WFN affected absolute and relative SATs. Increasing modulation depth decreased absolute and relative SATs (i.e., the noise was less acceptable for sleep). The older group and WFN-highly sensitive participants had the lowest SATs with no difference in relative SATs. Interestingly, the road-traffic-noise-sensitive group simultaneously showed the lowest relative SATs and the highest absolute SATs. Low relative SATs of 7.5 ± 2.1 dBA (mean ± CIs) were obtained for less sleepy participants at a modulation depth and tonal audibility of 15 dBA and a modulated frequency of 110 Hz.

Absolute and relative SATs with broadband AM WFN were also examined. The increase of modulation depth of broadband AM WFN decreased absolute and relative SATs. Relative SATs started at 0 for a modulation depth of 2 dBA and increased gradually and reached relative SATs of 6.8 ± 1.8 dBA (mean ± CIs) at a modulation depth of 10 dBA and a baseline SAT range below 30 dBA.

Different types of masking background noise also affected absolute SATs of WFN (F (3, 422) = 21.5, p < 0.001). Short-range RTN masking increased WFN sleep acceptability by (mean ± CIs) 3.0 ± 1.5 dBA for noise-sensitive groups. Unlike other groups, RTN-sensitive participants found WFN more acceptable for sleep when mixed with short-range RTN at 47 ± 1.5 dBA.

The effects of WFN acoustic characteristics and related human factors on sleep acceptability are important considerations for future WFN guideline developments. The outcomes of this thesis work provide important new data towards guiding evidence-based improvements to noise guidelines and penalties for WFN characteristics and choosing suitable sites for wind farms based on pre-existing ambient noise.

Keywords: wind energy, wind farm noise, wind turbine noise, psychoacoustics, annoyance, sleep acceptability

Subject: Science, Technology and Enterprise thesis

Thesis type: Doctor of Philosophy
Completed: 2022
School: College of Science and Engineering
Supervisor: Mark Taylor