Sound surrounds and envelops us, whether we are indoors or out, at work or at play, in cities or in the country. We hear voices, vehicles, birds, wind in trees, machinery, footsteps, raindrops, telephones, the hum and beeps of our electronics, dogs barking, and sometimes the sound of blood moving through our bodies. Sound, through speech, is still the medium of much of our communication with others, despite the ubiquity of message texts and emails. Sound is always present, and our ears are always switched on, even when we are asleep. We share an acoustic environment with any who occupy the same indoor or outdoor space that we do. This book is primarily about the acoustic environments that we experience (when not cocooned in the private acoustic space of headphones and recorded sound) in all the places of our cities, suburbs and villages, countryside and natural areas. While much of the emphasis in this book is on sound in outdoor space, many of the observations, principles, and approaches will also apply to hybrid indoor-outdoor spaces-malls and markets, transport stations, sports stadia, museums, and the balconies of our own dwellings-and to indoor spaces in hospitals, educational institutions, restaurants, and even our dwellings. We have a particular focus in this book on the planning, design, and management of the environment of these areas, and human experience of them. Acoustic installations, and the recording of outdoor sound, as deliberate works of art, are not within the scope of this book.