(Greek: stereos = solid; phone = sound) Generally, a term used to refer to the spatial distribution of sound, normally using AUDIO technology. More specifically, a form of reproduction which records, transmits and reproduces the original sound with two CHANNELs, regardless of the number of loudspeakers used. Also abbreviated to stereo.
Sound at frequencies above the audible range, namely above 20 kHz, audible only to various non-human species. Because of its very short WAVELENGTH in the megahertz range, ultrasound is used as a safe alternative to X-ray photography in medical diagnosis. Ultrasound scanning is sometimes called sonography.
When sounds are conducted separately and independently to each ear via tubes or headphones, the sounds are said to be heard dichotically. In various psychoacoustic experiments, isolation of the function of each ear is desirable, such as in the testing or simulation of BINAURAL HEARING with the PRECEDENCE EFFECT, or in testing preferences for different sounds presented simultaneously to separate ears.
A form of STEREOPHONIC or multi-channel reproduction in which the sound source is spread around the listener by the use of four tracks or CHANNELs in recording or transmission and the use of four (or more) LOUDSPEAKERs. Conventional music or speech may be recorded in this way, in which case the speakers behind the listener add REVERBERATION to the original sound or are simply out of PHASE with respect to the front ones; or new works may be composed in which all tracks carry original material.