IPA meaning in Radio Science ?

The International Phonetic Alphabet (IPA) is an alphabetic system of phonetic notation based primarily on the Latin script. It was devised by the International Phonetic Association in the late 19th century as a standardized representation of speech sounds in written form. The IPA is used by lexicographers, foreign language students and teachers, linguists, speech–language pathologists, singers, actors, constructed language creators and translators.

The IPA is designed to represent those qualities of speech that are part of lexical (and to a limited extent prosodic) sounds in oral language: phones, phonemes, intonation and the separation of words and syllables. To represent additional qualities of speech, such as tooth gnashing, lisping, and sounds made with a cleft lip and cleft palate, an extended set of symbols, the extensions to the International Phonetic Alphabet, may be used.

IPA symbols are composed of one or more elements of two basic types, letters and diacritics. For example, the sound of the English letter ⟨t⟩ may be transcribed in IPA with a single letter, [t], or with a letter plus diacritics, [t̺ʰ], depending on how precise one wishes to be. Slashes are used to signal phonemic transcription; thus /t/ is more abstract than either [t̺ʰ] or [t] and might refer to either, depending on the context and language.

Occasionally letters or diacritics are added, removed or modified by the International Phonetic Association. As of the most recent change in 2005, there are 107 segmental letters, an indefinitely large number of suprasegmental letters, 44 diacritics (not counting composites) and four extra-lexical prosodic marks in the IPA. Most of these are shown in the current IPA chart, posted below in this article and at the website of the IPA.