Kleiner M., Tichy J. Acoustics of Small Rooms

CRC Press, 2014. — 478 p.In this book, we focus on sound in small rooms that have interior volumes in the range from a few cubic meters to a few hundred cubic meters. Thus, rooms as diverse as car cabins and small lecture rooms, reverberation and anechoic chambers might fit the description. Better and acoustic definitions of small rooms could be rooms in which the individual resonances of the room must be considered at low frequencies, or rooms in which the early reflections by walls, ceiling, and room objects arrive within milliseconds of the direct sound.
The sound reproduction in a room is determined by the room’s resonances (often called modes). The resonances are damped by sound absorption in the room, and their decay is noted as reverberation. With many resonances per unit frequency, the subjective response of the room is heard as smooth. In a small room, such as a car compartment, there are only about 10 resonances below 200 Hz, but in a concert hall there will be many more resonances. We can still play back the concert hall recording in the car, but the reproduced sound of the low frequencies of the instruments will sound tainted or colored.
Also, the way the room affects the time history of voice and music is important subjectively. When the resonances are well damped, the time history for the reflections arriving at the listener will make the difference between a well-sounding room and one in which there is coloration or even flutter echo. The way that the room directs the sound from the source, musical instrument, voice, or loudspeaker is essentially determined by the reflecting surfaces of the room and its in-room objects, and their acoustical characteristics. A person, the listener, for example, will absorb and scatter sound, so it is never possible to measure or reproduce exactly the sound simply for the reason that humans move around.
Surround sound, stereo, Hi-Fi systems are all attempts at producing what one audio equipment manufacturer called … the closest approach to the original sound. As humans, we are multisensory receptors. We hear, but unavoidable tactile and visual information is added to our listening experience. In addition, we use cognition when judging the quality and characteristics of audio and acoustics. The closest approach to the original sound may not be enough for emotionally equivalent small room reproduction of the sound recorded in a concert hall.Physics of small room sound fields
Sound fields in enclosures
Geometrical acoustics
Sound absorption in rooms
Diffusion
The ear
Psychoacoustics
Spatial hearing
Sound reproduction in small rooms
Low-frequency sound field optimization
Rooms for sound reproduction
Small rooms for voice and music practice
Modeling of room acoustics
Measurement