Table 2.

Summary of measurement procedures for segmental and suprasegmental speech measures.

Perceptual dimension		Measure	Procedures
Segmental	Imprecise articulation: vowel distortion	F2 range of diphthongs	For the six diphthongs produced, F2 trajectories were generated using linear predictive coding in TF32. F2 range (max F2–min F2) was calculated for each diphthong and then averaged across the six diphthongs to obtain an average F2 range for each child.
	Imprecise articulation: consonant distortions/omissions	Proportion of bursts produced	For 18 plosive consonants, the presence of bursts was determined through visual judgments of screenshots of the spectrogram and waveform for each five-word sentence, without accompanying audio. Locations of target bursts were marked using red lines along the bottom of the spectrogram. Bursts were operationally defined as a distinct line of energy extending across at least 50% of the frequency range present within the target window. For each child, proportion of bursts = number of bursts produced / number of target consonants.
	Imprecise articulation: consonant voicing errors	Closure interval voicing	For seven postvocalic voiceless stops, duration of closure interval voicing was measured as the time between the point of closure and the end of voicing (i.e., the point at which glottal pulses terminated). These values were divided by closure interval duration to yield a proportion of persistent closure interval voicing for each target consonant. Proportions were then averaged across the set of target consonants to obtain an average proportion of closure interval voicing for each child.
Suprasegmental	Breathy, harsh, or strained/strangled voice quality	Proportion of deviant voice quality	Each of the 10 sentences produced by each child was perceptually judged for the presence of deviant voice quality. For each sentence identified as containing deviant voice quality, the durations of deviant voice segments were acoustically measured. The proportion of deviant voice quality (summed duration of deviant voice segments/utterance duration [excluding pauses]) was calculated for each sentence and then averaged across the 10 sentences to obtain an average proportion of deviant voice quality for each child.
	Hypernasality	Nasality rating	Ten SLPs listened to recordings of each child producing the set of five-word sentences and provided a rating for each child's degree of hypernasality on a 7-point Likert scale (1 = normal nasality, 7 = severe hypernasality).
	Slow rate	Articulation rate	For each of the 10 sentences produced, articulation rate was quantified as rate of speech (in syllables per second), exclusive of silent intervals longer than 200 ms. Rate was calculated for each sentence as the number of syllables divided by the corrected utterance duration (total utterance duration − summed pause duration). Articulation rate was averaged across the 10 sentences to yield an average articulation rate for each child.