Last update: May 22, 2017

Bob Thorne, PhD May 2014 AustraliaAustralia

Wind Farm Noise and Human Perception - A Review

Peer-reviewed document by Dr. Bob Thorne of Noise Measurement Services.

Introduction

The design and placement of wind farms cause problems for wind farm developers and residents directly from:

  • Inappropriate land-use planning;
  • lack of understanding of the problems involved with inadequate acoustical and human perception analysis; and
  • ineffective compliance approvals.

Inappropriate Land-use Planning

The general theme appears to be that if a wind farm is in a rural environment it can do no harm. Following this logic it is far better that the wind farm be located within the urban area that requires the power. The cost of development is lower, access to a large pool of labour is assured, access to materials and roading is no problem, and there are no adverse environmental effects from wind turbine noise. Turbine efficiency is not an issue as the wind farm and turbine choice can be designed for the relevant air and building environments. It is, therefore, a matter of land-use choice and associated planning instruments that brings turbines into rural areas rather that the urban areas where the power is needed.

The Problems with Wind Farm Noise and Its Perception

The sound from a wind farm is unique. It is not similar to air conditioning fan noise although it shares some of the low frequency characteristics of fan noise. It is not the same as noise from transportation sources (road, rail, aircraft) although it does share some of the ‘movement’ characteristics of these sources. The sound is of low amplitude and varies in space (as the blades turn), in location (as the blades turn with the different wind directions), in time (sound levels vary due to turbine activity over time), and in complexity (when the blades interact with disturbed air from other turbines). Turbines are large industrial noise sources. The height from ground to the centre of the hub can often be 80 to 85 metres and the blades themselves can be 46 to 50+ metres in length. The blades move and interact with a huge volume of air to draw energy from air movement to generate electricity.

The sounds from a wind farm are often of low amplitude (volume or loudness) and are constantly shifting in character (“waves on beach”, “rumble-thump”, “plane never landing”). People who are not exposed to the sounds of a wind farm find it very difficult to understand the problems of people who do live near to wind farms. Some people who live near wind farms are disturbed by the sounds of the farms, others are not. In some cases adverse health effects are reported, in other cases such effects do not appear evident. The sound from a wind farm is intermittent in that it is not constant all day every day at approximately the same level. The sound fluctuates with the wind. It changes as the turbines turn into the wind. Many people living near turbines do not become used to the variations or character of the sound - unlike traffic noise, for example, where people do become used to the relatively consistent character of the sound. The sound becomes unsustainable and in affected individuals can result in serious adverse health effects. Unfortunately, unlike with fan or transportation noise, there are no long established noise exposure models that will give any certainty of prediction as to the effect of wind turbines noise on people. There is an international standard that explains how to measure the sound from a turbine but the standard is limited in its application to noise assessment near the turbine; not at a distance. The standard does not address the core issue of the effect of such noise on people.

Ineffective Compliance Approvals

An effective compliance approval is one that applies conditions to specifically avoid adverse environmental outcomes. A partly effective compliance approval is one that mitigates adverse environmental outcomes. An ineffective compliance approval is one that permits or encourages adverse environmental outcomes. Professional experiences have been with wind farm compliance conditions that fall into this latter category as they have been so drafted that specific conditions cannot be measured with certainty. In particular, this applies to penalties imposed if a sound is tonal or has some special characteristic that must be identified. There are two situations that involve compliance monitoring: on an audit basis to identify compliance with noise conditions; or, on complaint. The only possible way to prove compliance is to turn the turbines off, measure the ambient levels, turn the turbines on, measure the wind farm and ambient sound levels together, assess the variation and then come to some decision as to compliance. This procedure only applies to an audit process and fails, of course, if noise complaints are being investigated when the wind farm noise and the ambient sound are completely mixed together and the wind farm sound is not clearly dominant. Secondly, and most importantly, the conditions giving rise to the complaint or complaints have gone and cannot be measured or assessed unless recorded.

When noise compliance is referenced to wind speed at the wind farm in practice only the wind farm operator has access to the wind and turbine data necessary to assess compliance. Thus it is virtually impossible for the “other side” be they regulatory authorities or complainants to prove non-compliance. There needs, therefore, to be a regulatory mechanism that is fair and practical to both the wind farm operator and to an individual affected by wind farm noise.

All of these issues are addressed further in this Review.

Wind Farm Noise and Human Perception
A Review

Contents

PART I - INTRODUCTION 6

Inappropriate Land-use Planning 6

The Problems with Wind Farm Noise and Its Perception 6

Ineffective Compliance Approvals 7

PART II - A CASE STUDY 8

A Rural Wind Farm 8

Prediction of Wind Farm Sound Levels 9

Case study with a Waubra residence 9

Background sound levels 11

The Effects of Weather 13

Audible sound character 13

Sound character at residence and near locale 15

Conclusions from Waubra Case Study 25

PART III - WIND FARMS AND HEALTH EFFECTS 26

PART IV - WIND TURBINE SOUND 36

Basic Measures 36

Wind Farm Noise 37

Low frequency sound and Infrasound 44

Heightened Noise Zones 47

PART V - PREDICTION OF SOUND LEVELS – APPROACHES AND LIMITATIONS 52

Consideration of Variable Wind Conditions 55

Wind Farm Noise` Standards 57

PART VI - RESPONSES OF RESIDENTS NEAR WIND FARMS 60

Community and Individual Noise Exposure 60

The Effects on People near the Waubra Wind Farm, Victoria 61

Conclusion 62

The Effects on People near the “West Wind’ wind farm, New Zealand 66

The Effects on People near the ‘Te Rere Hau’ Wind Farm, New Zealand 73

Real-world noise compliance problem at a wind farm 77

The Effects on People near the proposed Turitea Wind Farm, New Zealand 78

The Effects on People near the Waterloo wind farm, South Australia 80

INDIVIDUALS’ PERCEPTION O PART VII - F WIND FARM SOUNDS 83

Introduction 83

The Manawatu – Brisbane Pilot Study 83

A Study of Noise Sensitivity vs. Specific Sounds 86

Noise Annoyance 87

Makara and Waubra studies into adverse health effects 89

Community perception and acceptance of wind farms 89

PART VIII - ANNOYANCE, AUDIBILITY, LOW AND INFRASOUND PERCEPTION 91

Amenity and costs imposed by rural wind farms 93

Sound Perception 93

Annoyance 96

Audibility – Low frequency - Infrasound 99

PART IX - MEASUREMENT SYSTEMS 104

Character of sound 106

PART X - NOISE MANAGEMENT 110

PART XI - WIND FARM GENERATED NOISE AND ADVERSE HEALTH EFFECTS 114

PART XII - GLOSSARY 146

RECOMMENDED READING 152

Wind Farm Noise and Human Perception
A Review
Bob Thorne, PhD — Wind Farm Noise and Human Perception - A Review