Effect of modulation depth, frequency, and intermittence on wind turbine noise annoyance

Abstract

Amplitude modulation (AM) may be an important factor for the perceived annoyance of wind turbine noise (WTN). Two AM types, typically referred to as "normal AM" (NAM) and "other AM" (OAM), characterize WTN AM, OAM corresponding to having intermittent periods with larger AM depth in lower frequency regions than NAM. The extent to which AM depth, frequency, and type affect WTN annoyance remains uncertain. Moreover, the temporal variations of WTN AM have often not been considered. Here, realistic stimuli accounting for such temporal variations were synthesized such that AM depth, frequency, and type, while determined from real on-site recordings, could be varied systematically. Listening tests with both original and synthesized stimuli showed that a reduction in mean AM depth across the spectrum led to a significant decrease in annoyance. When the spectrotemporal characteristics of the original far-field stimuli and the temporal AM variations were taken into account, the effect of AM frequency remained limited and the presence of intermittent OAM periods did not affect annoyance. These findings suggest that, at a given overall level, the AM depth of NAM periods is the most crucial AM parameter for WTN annoyance.

Short-term annoyance reactions to stationary and time-varying wind turbine and road traffic noise: A laboratory study

“…In addition, also AM (partly) determines annoyance. The increased annoyance reactions to WTN with periodic AM are in agreement with previous studies (Lee et al, 2011;RenewableUK, 2013;Ioannidou et al, 2016). The limited influence of AM in the case of RTN (Figs.…”

Health Effects Related to Wind Turbine Sound, Including Low-Frequency Sound and Infrasound

“…These are 10 on field studies [36,[61][62][63][64][65][66][67][68][69], 7 on experiments [12,[70][71][72][73][74][75], 3 on a prospective cohort study [76][77][78], 1 panel study [79] and 1 qualitative analysis of interviews and discourse [80]. After the systematic literature search, two relevant papers from the most recent International Wind Turbine Noise Conference (Rotterdam 2017) were included [43,81].…”

“…Ionannidou et al [72] report on a study among 19 volunteers in which the effect of changes over time in the amplitude modulation of wind turbine sound on annoyance was investigated. The changes could either be the frequency of the modulation, the depth (or strength) of the modulation or a change in depth over time.…”

“…Residential wind turbine sound levels themselves are modest when compared to those from other sources such as road or industrial sound. However, recent laboratory studies [12,71,72] are inconclusive regarding the effect of amplitude modulation on annoyance. One conclusion is that 'there is a strong possibility that amplitude modulation is the main cause of the properties of wind turbine noise', in which properties refer to sounds that are easily detectable and highly annoying at relatively low sound levels [12].…”

“…One conclusion is that 'there is a strong possibility that amplitude modulation is the main cause of the properties of wind turbine noise', in which properties refer to sounds that are easily detectable and highly annoying at relatively low sound levels [12]. Another dismisses amplitude modulation as a negative factor per se because it is highly related to attitude [72]. A common factor is that AM appears to aggravate existing annoyance, but does not lead to annoyance for persons positive about or benefiting from wind turbines.…”