Chirp

A chirp is a signal in which the frequency increases (up-chirp) or decreases (down-chirp) with time. In some sources, the term chirp is used interchangeably with sweep signal. It is commonly used in sonar and radar, but has other applications, such as in spread-spectrum communications. In spread-spectrum usage, surface acoustic wave (SAW) devices such as reflective array compressors (RACs) are often used to generate and demodulate the chirped signals. In optics, ultrashort laser pulses also exhibit chirp, which, in optical transmission systems, interacts with the dispersion properties of the materials, increasing or decreasing total pulse dispersion as the signal propagates. The name is a reference to the chirping sound made by birds; see bird vocalization.

Types

Linear

In a linear chirp, the instantaneous frequency varies linearly with time:

where is the starting frequency (at time ), and is the rate of frequency increase or chirp rate.

where is the final frequency and is the starting frequency. is the time it takes to sweep from to .

Chirp (magazine)

Chirp Magazine is a popular Canadian children’s magazine founded in 1997. Aimed at those between the ages of 3 and 6, it is published 10 times per year.

Chirp is the youngest member in a family of magazines that includes OWL and chickaDEE. Regular features include crafts, jokes, puzzles, fiction, and the comics "The Vole Brothers" and "Chirp and Friends," which features the adventures of the magazine's namesake, a large yellow bird.

Chirp, like OWL and chickaDEE, is published by Owlkids and owned by Bayard Canada. Bayard also owns a number of French children’s publications, including Les Débrouillards and Les Explorateurs.

Television

In January 2012, Toronto-based animation studio Yowza announced that it is collaborating with Owlkids and the Canadian Broadcasting Corporation to develop a preschool television series based on the magazine.

References

External links

Bird vocalization

Bird vocalization includes both bird calls and bird songs. In non-technical use, bird songs are the bird sounds that are melodious to the human ear. In ornithology and birding, (relatively complex) songs are distinguished by function from (relatively simple) calls.

Definition

The distinction between songs and calls is based upon complexity, length, and context. Songs are longer and more complex and are associated with courtship and mating, while calls tend to serve such functions as alarms or keeping members of a flock in contact. Other authorities such as Howell and Webb (1995) make the distinction based on function, so that short vocalizations, such as those of pigeons, and even non-vocal sounds, such as the drumming of woodpeckers and the "winnowing" of snipes' wings in display flight, are considered songs. Still others require song to have syllabic diversity and temporal regularity akin to the repetitive and transformative patterns that define music. It is generally agreed upon in birding and ornithology which sounds are songs and which are calls, and a good field guide will differentiate between the two.