Voiceless consonants (fortis) are characterized acoustically as tense and voiced (lenis) as lax, since the burst of noise in voiced plosives and the formant of noise in voiced fricatives are less strong than those in voiceless plosives and fricatives.

The noise peculiar to alveolar and dental consonants /t, d, s, z, n, l, , ð/ is contrasted with that of labial and labio-dental ones /p, b, m, f, v/ because it is sharper in character. This means that in the spectra of /t, d, s, z, n, l, , ð/ high frequencies are predominant and in the spectra of /p, b, m, f, v / the formant of noise is lower.

The fricatives (alveolar and dental) /s, z, , ð/ have the highest frequencies of noise in the spectrum-up to 8000 cps. The frequencies of the noise formant in the spectrum of /f, v/ are low. Therefore, /t, d, s, z, , ð, n/ are characterized as acute and /p, b, m, v/, as grave. The consonants /k, g, , ʒ, t, ʤ/ are intermediate in this contrast.

The spectrum of velar and palatal consonants / k, g, ŋ, , ʒ, t, ʤ/ is compact while the spectrum of alveolar, labial and dental ones /t, d, n, s, z, m, p, b, f, v, , ð/ is diffuse. Consequently, the former are classified as compact consonants and the latter as diffuse ones.

The sonants /m, n, ŋ/are opposed to all the other consonants as nasal to oral, because in their spectrum there is a special nasal formant.

The consonants /s, z/ having a round narrowing are opposed to /, ð/ having a flat narrowing and the affricates /t, ʤ/ are opposed to the plosives /t, d/ as strident to mellow. In the spectrum of strident consonants the intensity of noise formant is greater in the spectrum of mellow consonants.

Dichotomic Classification of the Acoustic Distinctive Features of English Consonant Phonemes and its Articulatory Correlates