Acoustic phonetics in the context of "The Sounds of the World's Languages"

Phonetics is a branch of linguistics that studies how humans produce and perceive sounds or, in the case of sign languages, the equivalent aspects of sign. Linguists who specialize in studying the physical properties of speech are phoneticians. The field of phonetics is traditionally divided into three sub-disciplines: articulatory phonetics, acoustic phonetics, and auditory phonetics. Traditionally, the minimal linguistic unit of phonetics is the phone—a speech sound in a language which differs from the phonological unit of phoneme; the phoneme is an abstract categorization of phones and it is also defined as the smallest unit that discerns meaning between sounds in any given language.

Phonetics deals with two aspects of human speech: production (the ways humans make sounds) and perception (the way speech is understood). The communicative modality of a language describes the method by which a language produces and perceives languages. Languages with oral-aural modalities such as English produce speech orally and perceive speech aurally (using the ears). Sign languages, such as Australian Sign Language (Auslan) and American Sign Language (ASL), have a manual-visual modality, producing speech manually (using the hands) and perceiving speech visually. ASL and some other sign languages have in addition a manual-manual dialect for use in tactile signing by deafblind speakers where signs are produced with the hands and perceived with the hands as well.

Auditory feedback (AF) is an aid used by humans to control speech production and singing by helping the individual verify whether the current production of speech or singing is in accordance with his acoustic-auditory intention. This process is possible through what is known as the auditory feedback loop, a three-part cycle that allows individuals to first speak, then listen to what they have said, and lastly, correct it when necessary. From the viewpoint of movement sciences and neurosciences, the acoustic-auditory speech signal can be interpreted as the result of movements (skilled actions) of speech articulators (the lower jaw, lips, tongue, etc.). Auditory feedback can hence be inferred as a feedback mechanism controlling skilled actions in the same way that visual feedback controls limb movements (e.g. reaching movements).

Auditory phonetics is the branch of phonetics concerned with the hearing of speech sounds and with speech perception. It thus entails the study of the relationships between speech stimuli and a listener's responses to such stimuli as mediated by mechanisms of the peripheral and central auditory systems, including certain areas of the brain. It is said to compose one of the three main branches of phonetics along with acoustic and articulatory phonetics, though with overlapping methods and questions.

Ludimar Hermann (October 31, 1838 – June 5, 1914) was a German physiologist and speech scientist who used the Edison phonograph to test theories of vowel production, particularly those of Robert Willis and Charles Wheatstone. He coined the word formant, a term of importance in modern acoustic phonetics. The Hermann grid is named after him; he was the first to report the illusion in scientific literature.