After identifying a message to be linguistically encoded, a speaker must select the individual words-known as lexical items-to represent that message in a process called lexical selection. Language production consists of several interdependent processes which transform a non-linguistic message into a spoken or signed linguistic signal. 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. 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 (using the eyes). Languages with oral-aural modalities such as English produce speech orally (using the mouth) and perceive speech aurally (using the ears). The communicative modality of a language describes the method by which a language produces and perceives languages. Phonetics broadly deals with two aspects of human speech: production-the ways humans make sounds-and perception-the way speech is understood. 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 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 ( articulatory phonetics), how various movements affect the properties of the resulting sound ( acoustic phonetics), or how humans convert sound waves to linguistic information ( auditory phonetics). Phoneticians-linguists who specialize in phonetics-study the physical properties of speech. 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.

Praat sound to pitch