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.
For any PERIODIC wave the wavelength is the distance from a given point in the wave to the corresponding point in the next cycle of the wave, frequently represented by the Greek letter lambda. It may also be thought of as the distance the sound travels in one CYCLE or PERIOD.
In the perception of ACOUSTIC SPACE, projicience refers to the sense of depth of a sound in the space.
If two TONEs are about 15 Hertz or less apart, INTERFERENCE will result from their similar though not exactly identical frequencies. Gradually they will move out of PHASE until at 180