All segments were given an acoustic definition in the feature theories of Jakobson, Fant & Halle (1951) and Jakobson & Halle (1956). Many of the features were passed down to Chomsky & Halle (1968) where the definitions were supplemented with an articulatory definition. This table compares the articulatory and acoustic definitions of the J&H features, for example "consonantal" being "Low total energy" vs "Obstruction in vocal tract". The surmountable difficulty is figuring out what "compact" refers to. JFH say
Compact phonemes are characterized by the relative predominance of one
centrally located formant region (or formant). They are opposed to
diffuse phonemes in which one or more non-central formants or formant
In the case of the vowels this feature manifests itself primarily by
the position of the first formant (11): when the latter is higher
(i.e. closer to the third and higher formants), the phoneme is more
compact. The closer the first formant is to the upper formants, the
higher will be the intensity level of the region above the first
formant, especially the level between peaks.
In the consonants, compactness is displayed by a predominant formant
region, centrally located, as opposed to phonemes in which a
non-central region predominates; (cf. Fant's analysis of Swedish stops
(3)). The compact nasals have a dominant formant region between the
characteristic nasal formants (200 cps and 2500 cps), Delattre's
observations on the positions of the first formant in stops and nasal
consonants (12) corroborate the parallelism between the compactness
feature in vowels and consonants.
Formants are the filtering properties of a sound, defined by where the constrictions are. Both consonants and vowels have constrictions, so they have formants (well, h and ʔ don't have constrictions). However, figuring out where the formants are for a vowel is simple, not so much so for a consonant.
The distinction acute / grave applies to front / back vowels and labial/dental/velar consonants:
Acoustically this feature means the predominance of one side of the
significant part of the spectrum over the other. When the lower side
of the spectrum predominates, the phoneme is labeled grave; when the
upper side predominates, we term the phoneme acute.
Front vowels are acute, coronal consonants are acute: this matches the more recent equation of coronal qua V-place feature with "-back".