This article describes the essential properties of an acoustic theory of phonetics and demonstrates the dependence of such a theory on physiological phonetics. The article defines the acoustical characteristics of speech and summarizes the relationships of these characteristics to physiological speech parameters and to descriptive phonetics. The acoustical characteristics of speech are defined as the speech wave types and the acoustical speech parameters. The basic speech wave types specified are quiescent, burst, quasi-random, quasi-periodic, double-periodic, and irregular-periodic. The acoustical speech parameters are separated into acoustic phonetic parameters and acoustic prosodic parameters. The basic acoustic phonetic parameters are specified as gap, voice bar, broad-band continuous spectrum, the frequencies of the vowel and consonant formants, the amplitudes of the vowel and consonant formants, and the frequencies of the consonant antiresonances. The acoustic prosodic parameters are defined as acoustic phonetic duration, average fundamental voice frequency, and average speech power. The relationships among the speech wave types and the acoustical speech parameters are shown by means of a table. The essential relationships among the speech wave types, the acoustical speech parameters, and the physiological speech parameters are also shown in a set of tables. The manner in which the speech wave types and the acoustic phonetic parameter values may be employed to identify the phone types of descriptive phonetics is briefly discussed and illustrated.