Urban Forest Acoustics

In general, trees are viewed as admired symbolic individuals, producing rec- ational, spiritual and emotional rejuvenation. Their lifespan can far exceed that of humans. Planting a tree is a singular act of faith in the future, c- ating a legacy for the community members who will follow. The presence of trees in an urban area has been a reality for several centuries. Beautiful trees in urban plazas are synonymous with a high sense of community and civic pride. Trees signi?cantly enhance the landscaping and appearance of the built environment. City trees improve several architectural and engineering functions, prov- ing a green infrastructure for communities. Trees create a friendlier envir- ment for walking, riding bikes and working, by reducing glare and softening harsh traf?c sounds and concrete views. Trees enhance the viewing in urban areas of a variety of birds and small animals, such as squirrels. They are of extreme importance to the functioning of many different ecosystems. Trees planted in the right place around buildings can improve air conditioning and heating costs by providing shade or by affecting wind speed or direction. Ev- green trees with dense, persistent needles can be used to provide a windbreak, while deciduous trees allow the sun to warm a house in winter. The more c- pact the branches and foliage of a group of trees, the greater their in?uence as a windbreak.

1 Introduction 2 Noise in Urban Forest 2.1 Sound Propagation 2.1.1 Definition and Theoretical Considerations 2.1.2 Factors Affecting Sound Propagation 2.2 Equipment for Noise Measurement 2.2.1 Instrumentation and Noise Sources 2.2.2 Measurement In Situ 2.2.2.1 Effects of Distance 2.2.2.2 Effect of Frequency 2.2.2.3 Effect of Visibility 2.3 Summary 3 Tree Characteristics and Acoustic Sensors 3.1 Morphological Characteristics 3.2 Mechanical Characteristics 3.2.1 Devices and Instrumentation 3.2.2 Mechanical Characteristics of Standing Trees 3.2.3 Detection of Internal Defects in Standing Trees 3.2.3.1Ultrasonic Velocity Method 3.2.3.2 Stress Wave Method 3.3 Genotypic Characteristics 3.4 Sylvicultural Practices 3.5 Summary 4 Noise Attenuation with Plant Material 4.1 Physical Aspects of Noise Attenuation with Plants 4.2 Ground Attenuation 4.3 Scattering by Trees 4.3.1 Scattering by Stems 4.3.2 Scattering by Canopy and Foliage 4.3.2.1 Measurements in Anechoic Room 4.3.2.2 Measurements in Reverberation Room 4.3.2.3 Outdoor Measurements 4.3.3 Reverberation in a Forest Stand 4.3.4 Atmospheric Conditions 4.4 Sound Scattering by Barriers 4.4.1 Psychological Effects 4.4.2 Solid Barriers without Vegetation 4.4.3 Solid Barriers with Vegetation 4.5 Summary 5 Traffic Noise Abatement 5.1 Road Traffic Noise 5.2 Railway Transportation Noise 5.3 Aircraft Noise 5.4 Summary 6 Noise Abatement and Dwellings 6.1 Urban Area 6.2 Suburban Area 6.3 Summary 7 Noise, Birds and Insects in Urban Forest 7.1 Bird Acoustic Communication in Forest Environment 7.2 Detection of Termite Infestation in Urban Trees 7.3 Summary 8 Acoustics for Fire Control in Forest 9 Economic Aspects Annex 1 Symbols Annex 2 Some Theoretical Considerations Annex 3 Frequency Weighting Annex 4 Standards Annex 5 Units References Subject Index