Aspiration (phonetics)
From Freepedia
In phonetics, aspiration is the strong burst of air that accompanies the release of some obstruents. To feel or see the difference between aspirated and unaspirated sounds, put your hand or a lit candle in front of your mouth, and say top and then stop. You should either feel a puff of air or see a flicker of the candle flame with top that you do not get with stop. The t in top is aspirated; in stop it is unaspirated.
The diacritic for aspiration in the International Phonetic Alphabet is a superscript aitch, [ʰ]. Unaspirated consonants are not normally marked explicitly, but there is a diacritic for non-aspiraton in the Extended IPA, the superscript equal sign, [⁼].
English voiceless stops are aspirated when they begin a stressed syllable, as in pen, ten, Ken, but this is not distinctive. That is, these consonants have unaspirated variants in other positions, such as word-finally or after [s], as in spun, stun, skunk. In many languages, such as Cantonese, Hindi, Icelandic, Korean, Mandarin, Thai, and Ancient Greek, [p⁼ t⁼ k⁼] etc. and [pʰ tʰ kʰ] etc. are different phonemes altogether.
Alemannic German dialects have unaspirated [p⁼ t⁼ k⁼] as well as aspirated [pʰ tʰ kʰ]; the latter series are usually viewed as consonant clusters. In Danish and most southern varieties of German, the "lenis" consonants transcribed for historical reasons as <b d g> are distinguished them from their "fortis" counterparts <p t k> mainly in their lack of aspiration.
Icelandic has pre-aspirated [ʰp ʰt ʰk]; some scholars interpret these as consonant clusters as well.
The aspiration symbol is sometimes used with voiced stops, such as [dʰ]. However, such "voiced aspiration", also known as breathy voice or murmur, is less ambiguously transcribed with dedicated diacritics, either [d̤] or [dʱ]. (Some linguists restrict the subscript diacritic [ ̤] to sonorants, such as vowels and nasal consonants, which are murmured throughout their duration, and use the superscript [ʱ] for the murmured release of obstruents.)
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