In most species, the sound is produced by expelling air from the lungs over the vocal cords into an air sac or sacs in the throat or at the corner of the mouth.
ɪn mˈoʊst spˈiːsiːz, ðə sˈaʊnd ɪz pɹədˈuːst baɪ ɛkspˈɛlɪŋ ˈɛɹ fɹʌmðə lˈʌŋz ˌoʊvɚ ðə vˈoʊkəl kˈoːɹdz ˌɪntʊ ɐn ˈɛɹ sˈæk ɔːɹ sˈæks ɪnðə θɹˈoʊt ɔːɹ æt ðə kˈɔːɹnɚɹ ʌvðə mˈaʊθ.