The main sign of the retroflex in spectrograms is that F3 comes very close to F2, in the extreme case being swallowed up into it, and in either case restricting all significant energy below 2000 Hz (higher in females and children). /9r/ is different from /3r/ in that in /9r/, the formants show a great deal of movement; in intervocalic position F3 will swing down below 2000 Hz and back above it. In /3r/, the formants seem to move instantly together and to stay there as long as the syllable persists.
The phoneme /l/ shows a lot of variety in the spectrogram. Before a vowel, F3 may descend or stay even, while F2 rises, giving the phoneme a forked appearance. This is particularly true for the syllable `ly' as in ``daily." In other cases, the formants F2 and F3 move directly into the next vowel without any marked frequency variations, but the /l/ shows less energy than the vowel. There is often a clear spectral discontinuity where the tongue touches the alveolar ridge, causing the antiresonance to form, and again when it is taken away. In postvocalic contexts, /l/ is signalled by the crushing down of F2 with F1 near or below 1000 Hz, with F3 simultaneously moving up toward 3000 Hz, again leaving the hole in the normal F2 range. The two cases may be combined in the case of intervocalic /l/, where an elliptical low-energy pattern may be detected. /l/ is easy to confuse with /oU/.
Notice that in English we do not like combinations such as /th l/ or /d l/, although these exist in other languages. The voiced /z/ and /v/ occur in very few such combinations; again, this is probably an English preference since there are words such as zouave and voir in French.
In cases where the preceding consonant is voiceless, the glide or liquid may be partially or totally devoiced; in this case it is realized in aspiration bands rather than as voicing bands, and would be labelled phonetically as /j_0/, /w_0/, /9r_0/, or /l_0/. In all cases, the two phonemes interact and make recognition more difficult.