Quefrency

Part of speech: noun

Definitions

1. A quantity in signal analysis that measures how rapidly a periodic component repeats in the spectrum of a spectrum, the reciprocal of frequency used in cepstral processing
2. The term for the time-like measure found by taking the spectrum of a logarithmic spectrum, used to identify periodicity in a signal
3. In acoustics and speech processing, the unit describing the rate of repetition within a frequency spectrum, obtained as the reciprocal of frequency

Etymology: Quefrency is a deliberate joke built on a sound swap. It comes from "frequency" with the consonant sounds of its first two syllables switched, so the "f" and "kw" trade places. The word belongs to signal processing, where it names the time-like variable of a cepstrum, a result of taking a spectrum's logarithm and transforming it again. The coinage follows the pattern of "cepstrum" itself, which was formed from "spectrum" by the same kind of letter-swap, with the first syllables reversed. Quefrency was made to match, so that the terms for the spectral and cepstral domains would mirror each other. In the source's view, the new word was probably modelled on that earlier joke rather than invented in isolation.