acoustics

In general, the experimental and theoretical science of sound and its transmission; in particular, that branch of the science that has to do with the phenomena of sound in a particular space such as a room or theatre. In architecture, the sound-reflecting character of an internal space.

Acoustic engineering is concerned with the technical control of sound, and involves architecture and construction, studying control of vibration, soundproofing, and the elimination of noise. It also includes all forms of sound recording and reinforcement, the hearing and perception of sounds, and hearing aids.

Sound energy spreads as vibrations in the form of pressure waves that are absorbed by soft objects such as drapery and human bodies, and reflected by hard surfaces such as walls and ceilings. These reflections are known as echoes. In a well-designed auditorium the echoes bouncing around all hard surfaces arrive so frequently at the ear, finally dying down, that the listener registers them merely as a slight extension to the original sound. Echoes that are too distinct are undesired since they render the original sounds indistinct. Too much sound absorption by drapery makes for a dull, dead effect. Auditorium design must also allow the performer (or speaker or congregant, in a place of worship) to hear himself or herself and his or her neighbours if some sort of communication with others is desired; excessive ‘damping’ of sound is also unwanted for this reason. Special sound reflectors may be erected for orchestras or congregations to this end. Unwanted noise may be avoided by preventing floor vibration with carpeting, by soundproofing the building with the aid of double glazing or masking the outside of the building with planted trees, and by using sound ‘perfume’ in the form of piped music or ‘white noise’ such as waterfalls or fountains.