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. Phoneticians—linguists who specialize in studying Phonetics the physical properties of speech. The field of phonetics is traditionally divided into three sub-disciplines based on the research questions involved such as how humans plan and execute movements to produce speech, how various movements affect the properties of the resulting sound, or how humans convert sound waves to linguistic information. 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.
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. Sign languages, such as Australian Sign Language and American Sign Language, have a manual-visual modality, producing speech manually and perceiving speech visually.
Language perception is the process by which a linguistic signal is decoded and understood by a listener. In order to perceive speech the continuous acoustic signal must be converted into discrete linguistic units such as phonemes, morphemes, and words. In order to correctly identify and categorize sounds, listeners prioritize certain aspects of the signal that can reliably distinguish between linguistic categories. While certain cues are prioritized over others, many aspects of the signal can contribute to perception. For example, though oral languages prioritize acoustic information.
Modern phonetics has three branches:

• Articulatory phonetics, which addresses the way sounds are made with the articulators
• Acoustic phonetics, which addresses the acoustic results of different articulations
• Auditory phonetics, which addresses the way listeners perceive and understand linguistic signals