Phonetics and phonology are the two primary linguistic disciplines concerned with speech sounds. Phonetics describes the physical form and production of sounds, while phonology examines the functional role of sounds in a language. Sounds are classified as either consonants or vowels, where consonants involve obstruction of airflow in the mouth and vowels do not. The key difference is that vowels are generally voiced with vibrating vocal cords, while consonants can be either voiced or voiceless.