Vehicle horn horn. Bicycles often have a classic "bulb horn", operated by squeezing a rubber bulb attached to a metal horn. Squeezing the bulb forces air through a steel reed located in the throat of the horn, making it vibrate, producing a single note. The flaring horn matches the acoustic impedance of the reed to the open air, radiating the sound waves efficiently, making the sound louder. Other types of horns used on bicycles include battery-operated horns (sometimes even car horns on 12-volt circuits are incorporated) and small air horns powered by a small can of compressed gas. Oliver Lucas of Birmingham,
Archaic Greek alphabets , and was probably an intermediate sound during the phonetic change from the earlier plosive clusters towards the later sound, possibly an affricate similar to . In one attested document, the Arcadocypriot Greek of Mantineia used an innovative letter similar to И (), probably derived from a variant of san, to denote what was probably a -like sound in environments reflecting etymological Proto-Greek . In the highly-divergent Pamphylian Greek, the letter digamma () existed side by side with another distinctive form . It has been surmised that in this dialect the sound may have changed to labiodental in some environments.