This experiment tested whether locus equation coefficients, slope, and y-intercept could serve as indices of place ofarticulation for obstruents sharing the same place ofarticulation across different manner classes. Locus equations for 22 speakers were derived from eVltl words with initial voiced stop Idl, voiceless aspirated stop It/, nasal Inl, voiced fricative Izl, and voiceless fricative lsi preceding 10 vowel contexts. Post hoc tests revealed Idl = Izl = Inl for slope means. Voiced Idl and voiceless It I were also equivalent when F2 transition onset measurement points were equated. Scatterplots of locus equation coefficients revealed three nonoverlapping and distinct clusters when the diverse coronal group was compared with labials and velars. A discriminant analysis using slope and y-intercept as predictors successfully categorized all five coronals into one alveolar group with 87.1% accuracy. The collective results support the contention that locus equations can serve as effective phonetic descriptors of consonant place of articulation across manner classes.Locus equations are linear regressions of the onset of F2 transitions on their offsets measured in the vowel nucleus (Lindblom, 1963). Frequency coordinates coding F2 transitions ofallophonic variants ofa given stop place category (e.g., beat, bet, bat, boot, but, boat, bought, bait, etc.) This orderly plot captures a higher order and emergentlike acoustic commonality-namely, a vowel normalization of the F2 transition within each stop place category. Higher order locus equation coefficients-slope and yintercept-when serving as predictor variables in a discriminant analysis, were shown to correctly classify labial, alveolar, and velar stop place of articulation with 100% accuracy (Sussman et al., 1991 the slope of the regression function is proportional to the extent ofCV coarticulation being used by the speaker (see Figure 10 in Sussman et al., 1993). The consistently linear scatterplots, as documented across languages, gender, and speaking conditions, have recently been interpreted as possibly serving a functional role in speech perception and the representational encoding (viz., mapping) of acoustic-based place of articulation categories (Sussman, Fruchter, & Cable, 1995).The acoustic correlates of consonantal place of articulation, however, are many and varied. Burst information, onset spectra, and formant transition motion have all been implicated, to greater or lesser extents, as perceptual cues for place ofarticulation (see, e.g., Blumstein & Stevens, 1979, 1980Dorman, Studdert-Kennedy, & Raphael, 1977;Eek & Meister, 1995;Furui, 1986; KewleyPort, 1983;Lahiri, Gewirth, & Blumstein, 1984; Nossair & Zahorian, 1991;Ohde, Haley, Vorperian, & McMahon, 1995;Walley & Carrell, 1983). Locus-equation-based analyses can offer additional insights into the role of the F2 transition onset-offset combination as a contributing cue for consonant place of articulation. Though the taxonomic value of locus equations to date has primarily been as a phonetic descri...