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FIG. 7. A token of /b/ produced by a 5-year-old girl which yielded a negativevalue of Pd difference between Pc, pressure at closure, and Pr, pressureat release.Müller and Brown 1980 were unique in proposingmethods of measuring time-varying aspects of P io duringstop closures. The results of their own and subsequent aerodynamicmodeling e.g., Westbury, 1983; Westbury andKeating, 1986 suggested further that the time course of P ioincrease during stop consonants could provide informationon aerodynamic management of voiced stops. For these reasons,the current work employed the measure, proposed byMüller and Brown as a simple metric for capturing aspects ofP io pulse shape. Yet the data obtained here, as well as closeinspection of Müller and Brown’s own data, suggest that thismeasurement method may have limitations. Specifically,some of the measures used to calculate and n yieldedunexpected values. These primarily reflected two situations:Cases where Pd pressure difference between release andclosure and angle from average to release pressure werenegative. Pressure pulse depictions like those in Fig. 2 leadone to expect both to be positive. The next paragraphs brieflydescribe how these values came about.Negative values of Pd occurred in five tokens threefrom children, two from men; four of the five were in /b/.An example from a 5 year old is given in Fig. 7. This tokenalso had a negative . In this production, intraoral pressuredecreases right before release. Although these examples areinfrequent in our database, they appear to indicate that supraglottalmovements affecting pressure contours may be initiatedrather late during the closure.Whereas negative Pd was rare, negative was morecommon, occurring in 155 tokens 15% of the data forwomen and children combined. These were found acrossage groups 36%, 39%, and 26% came from women, 10 yearolds, and 5 year olds respectively, and were about equallydistributed across consonants 53% for /p/; 47% for /b/. Tokenswith negative also accounted for 12% of the men’sdata. Negative occurs when the rise from closure to averagepressure Pa is greater than the pressure difference betweenclosure and release Pd. Such values may also haveoccurred in Müller and Brown’s 1980 data: Their plotsshow some speaker averages close to zero, with standarddeviations consistent with negative values. The occurrence ofnegative changes the interpretation of : Higher values of may result not only from convex wave forms, but alsofrom pressure contours that fall between the time of averagepressure and the time of release. To determine whether valuesof negative affected the conclusions, all statistics basedon or n were rerun without tokens whose values werenegative. The results were similar or identical to the originalones, suggesting that the occurrence of negative does notaffect the general pattern of results in this work. Further,case-by-case review of these − tokens did not show them tobe atypical in ways other than their values; that is, theyappeared to represent legitimate data points. The main observationto be made here is that Müller and Brown’s measurementmethods may yield some paradoxical values, and may reflect not only the convex/concave nature of a pressurepulse. It appears that more work is needed on how best toassess the time-varying characteristics of intraoral pressuredata.V. CONCLUSIONSAn extensive literature, using VOT as well as other measures,has indicated that stop consonant voicing is more limitedin preschool children than in adults. This has been attributedto poor aerodynamic control in the context ofanatomical growth and physiological maturation, processeswhich persist into adolescence. The current study usedMüller and Brown’s 1980 measure to assess the relationshipbetween P io characteristics and stop consonant voicingin children and adults. Unexpectedly, measures of voicingand did not differ significantly across age groups. For the5 year olds, this may reflect limited sample sizes, but it appearsthat by 10 years of age, children have learned to producevirtually adult-like voicing patterns despite immaturephysical systems. The correlational patterns between andstop consonant voicing do suggest, however, that aerodynamiccontrol of voicing in children is still subject to morevariability than in adult speakers, and that some children,particularly at 5 years but maybe also at 10 years, have notyet learned to manipulate intraoral pressure as effectively asadults.When interspeaker variability is taken into account, values for the current adult speakers seem consistent withthose of Müller and Brown 1980, although varying stimulusmaterials may have yielded some differences between thetwo studies. More interesting is that issues arose relative tothe measure itself. Paradoxical values of appear to haveoccurred in Müller and Brown’s data as well as our own.Although these difficulties do not negate the conclusions ofMüller and Brown regarding mechanisms of pressure controlin adults, they do suggest that new methods of assessingtime-varying characteristics of intraoral pressure data shouldbe devised in order to characterize the data more fully andappropriately. Future work should explore this topic further.ACKNOWLEDGMENTSSeveral students from Long Island University, BrooklynCampus and New York University contributed to recordingand data analysis for this project. In alphabetical order: GiridharAthmakuri, Jesse Farver, Linda Greenwald, Ingrid Katz,Karen Keung, Elizabeth Perlman, Simcha Pruss, and GabrielleRothman see Rothman, et al., 2002. Thanks to Elaine1086 J. Acoust. Soc. Am., Vol. 123, No. 2, February 2008 L. L. Koenig and J. C. Lucero: Voicing and intraoral pressure