In physics, resonance is a phenomenon that occurs when a given system is driven by another vibrating system or external force to oscillate with greater amplitude at a specific preferential frequency.
, the fundamental frequency is the lowest frequency sinusoidal in the sum. In some contexts, the fundamental is usually abbreviated as f0 (or FF), indicating the
overtone is any frequency higher than the fundamental frequency of a sound.
The Doppler effect (or Doppler shift) is the change in frequency of a wave (or other periodic event) for a
ultrasound machine makes images so that organs inside the body can be examined. The machine sends out high-frequency sound waves, which reflect off body structures. A computer receives the waves and uses them to create a picture.
Infrasound, sometimes referred to as low-frequency sound, is sound that is lower in frequency than 20 Hz (hertz) or cycles per second, the "normal" limit of human hearing. Hearing becomes gradually less sensitive as frequency decreases, so for humans to perceive infrasound, the sound pressure must be sufficiently high.
beat is an interference between two sounds of slightly different frequencies, perceived as periodic variations in volume whose rate is the difference between the two frequencies.