Phonetics

Phonetics is the study of how speech sounds are made, how they travel as sound waves, and how they are heard. It is a part of linguistics, and its three main branches are articulatory phonetics (how sounds are produced), acoustic phonetics (the physical properties of the sound waves), and auditory phonetics (how sounds are perceived). Experts in this field are called phoneticians. The smallest unit in phonetics is the phone, which is a single speech sound. This is different from the phoneme, the smallest unit in phonology, which is an abstract, language-specific category of sounds that can change meaning.

The way a language is produced and perceived is its communicative modality. Spoken languages like English use an oral-aural modality, where sounds are made with the mouth and heard with the ears. Sign languages like Auslan and ASL use a manual-visual modality, where signs are made with the hands and seen with the eyes. Some sign languages also have a manual-manual dialect for tactile signing, used by deafblind people, where signs are both produced and felt with the hands. Phonetics also studies these aspects of sign languages, including tactile signing.

The first known study of phonetics was done by Sanskrit grammarians as early as the 6th century BCE. The scholar Pāṇini, around 350 BCE, wrote a four-part grammar that is still influential and is considered the most complete generative grammar of any language. His work described phonetic principles like voicing, explaining that resonance comes from tone when the vocal folds are closed, or noise when they are open. These principles are considered basic building blocks for his analysis. The Sanskrit study of phonetics is called Shiksha, defined in the Taittiriya Upanishad as covering sounds, accentuation, vowel quantity, consonant expression, balancing, and sound connection.

After Pāṇini, progress in phonetics was limited for a long time, apart from some work by Greek and Roman grammarians. The focus shifted from the difference between spoken and written language to the physical properties of speech alone. Interest revived around 1800, and the term "phonetics" was first used in its modern sense in 1841. New medical discoveries and recording devices allowed for more detailed data. This period saw Alexander Melville Bell develop a phonetic alphabet based on articulatory positions, called visible speech, which was used to teach deaf children to speak. Before audio recording, phoneticians relied on ear training and production training to ensure consistent transcriptions. They had to recognize and produce the sounds of the International Phonetic Alphabet. Bell also described vowels by height and backness, creating nine cardinal vowels. Phoneticians were trained to produce these vowels as anchors for fieldwork. In the 1960s, Peter Ladefoged challenged this, showing through experiments that cardinal vowels were auditory targets, not articulatory ones.

Language production turns a nonlinguistic message into a spoken or signed signal. It is debated whether this happens in stages or in parallel. First, a speaker selects words (lexical items) based on their meaning, activating a lemma with semantic and grammatical information. Then, in phonological encoding, the words are given their phonological content as a sequence of phonemes.