Phonetics is the study of speech sounds. It investigates the physical properties of speech sounds, how they are produced by the vocal tract, and how people perceive these sounds. The field is typically divided into three areas: acoustic phonetics, auditory phonetics, and articulatory phonetics. Speech therapists are particularly concerned with articulatory phonetics.
There are many stuttering problems for people who stutter. People with an established stutter are aware of the negative effect of repetitions, prolongations, hesitations and blocks on their speech. Their stutter (stammer) may be accompanied by facial tics and uncontrolled body movements. Stuttering can lead to the avoidance of certain activities and to social isolation.