In phonetics, aspiration is the strong burst of breath that accompanies either the release or, in the case of preaspiration, the closure of some obstruents. In English, aspirated consonants are allophones in complementary distribution with their unaspirated counterparts, but in some other languages, notably most South Asian languages (including Indian ones) and East Asian languages, the difference is contrastive. In dialects with aspiration, to feel or see the difference between aspirated and unaspirated sounds, one can put a hand or a lit candle in front of one's mouth, and say spin and then pin . One should either feel a puff of air or see a flicker of the candle flame with pin that one does not get with spin. Transcription In the International Phonetic Alphabet (IPA), aspirated consonants are written using the symbols for voiceless consonants followed by the aspiration modifier letter , a superscript form of the symbol for the voiceless glottal fricative . For instance, represents the voiceless bilabial stop, and represents the aspirated bilabial stop. Voiced consonants are seldom actually aspirated. Symbols for voiced consonants followed by , such as , typically represent consonants with murmured voiced release (see below). In the grammatical tradition of Sanskrit, aspirated consonants are called voiceless aspirated, and breathy-voiced consonants are called voiced aspirated. There are no dedicated IPA symbols for degrees of aspiration and typically only two degrees are marked: unaspirated and aspirated . An old symbol for light aspiration was , but this is now obsolete. The aspiration modifier letter may be doubled to indicate especially strong or long aspiration. Hence, the two degrees of aspiration in Korean stops are sometimes transcribed or and , but they are usually transcribed and , with the details of voice onset time given numerically. Preaspirated consonants are marked by placing the aspiration modifier letter before the consonant symbol: represents the preaspirated bilabial stop. Unaspirated or tenuis consonants are occasionally marked with the modifier letter for unaspiration , a superscript equals sign: . Usually, however, unaspirated consonants are left unmarked: . Phonetics Voiceless consonants are produced with the vocal folds open (spread) and not vibrating, and voiced consonants are produced when the vocal folds are fractionally closed and vibrating (modal voice). Voiceless aspiration occurs when the vocal folds remain open after a consonant is released. An easy way to measure this is by noting the consonant's voice onset time, as the voicing of