chirp

Chirp is a term that refers to a short, high-pitched sound produced by many birds and insects, and it is also used in science to describe certain kinds of time-varying signals. The word imitates the rapid, bright tone of a small bird's call and has been in use in English since at least the 17th century.

In biology, chirps are common vocalizations used for communication. Birds such as sparrows, warblers, and finches emit chirp-like notes, while insects such as crickets and cicadas produce chirps through wing or body movements. Chirp patterns can convey species identity, mating readiness, or territorial presence, and chirp rate often correlates with temperature and activity.

In signal processing, a chirp is a signal in which the instantaneous frequency changes over time. A linear chirp is commonly described by f(t) = f0 + k t for t in [0, T], with instantaneous frequency ramping at rate k, and phase φ(t) = 2π (f0 t + 0.5 k t^2).

Chirped signals are widely used in radar, sonar, and communications because they provide large time–bandwidth products and enable pulse compression: a long, low-peak-power pulse can be compressed to high resolution at reception. Variants include exponential and logarithmic chirps, which alter the rate of frequency change and are chosen to match system requirements.

Beyond engineering, the term chirp remains a generic description of any short, sharp call resembling a birdlike trill, and its precise meaning depends on the context (biology, acoustics, or signal processing).