Books worth buying one of:
Johnson, K. (1997) Acoustic and Auditory Phonetics. Blackwell.
Ladefoged, P. (2001) Vowels and Consonants: an introduction to the sounds of languages. Blackwell.
Fry, D. B. (1979) The Physics of Speech. Cambridge University Press.
Ladefoged, P. (1962) Elements of Acoustic Phonetics. University
of Chicago Press.