Abstract The present work discusses waves and impedances, the determination of sound power levels and directivity, outdoor sound propagation, sound in small enclosures, noise in rooms, soundabsorbing materials and sound absorbers, the interactions of sound waves Abstract The present work discusses waves and impedances, the determination of sound power levels and directivity, outdoor sound propagation, sound in small enclosures, noise in rooms, soundabsorbing materials and sound absorbers, the interactions of sound waves