Perception of speaker sex, age, and vocal effort - Stockholms ...

Perception of speaker sex, age, and vocal effortHartmut TraunmüllerInstitutionen för lingvistik, Stockholms universitetAbstractSpeech material recorded for the purpose of studying the acoustic properties ofspeech as a function of speaker sex, age, and vocal effort (induced by varying thedistance between speaker and listener over a wide range) was used in perceptionexperiments in which the subjects had to rate either the distance between speaker andlistener or the age and the sex of the speaker. The correlations between these perceptsand gross spectral and temporal properties of the utterances, such as the mean valuesof F 0 , F 1 , and F 3 , spectral emphasis and utterance duration were analysed.IntroductionIt is well known that the acoustic properties of speech sounds vary not only because oflinguistic factors, but also as a function of organic, expressive, and transmittal factors(Traunmüller, 1997). The present contribution concerns the perception of the mostprominent organic variables, speaker sex and age, and the most prominent expressivevariable, vocal effort. While the perception of speaker sex and age has beeninvestigated previously, that of vocal effort has not been studied directly. However, theresults of Wilkens and Bartel (1979), who showed that listeners are able to recreatethe original SPL of a speaker from a recording with high precision, imply that listenersperceive vocal effort precisely irrespective of the SPL at their ears (or loudness),which is the most prominent transmittal variable.The present investigation shall also illuminate the question of how the variousparalinguistic qualities are perceived when none of the other is kept constant. How isvocal effort perceived when all the acoustic variables involved vary just as much as afunction of speaker age and sex? F 0 has sometimes be claimed to be most important forthe perception of speaker sex and age - but what if it varies just as much due tovariation in vocal effort or when the speaker whispers? And how can listenersdistinguish between variation in age and in sex, which appears to have quite similareffects on all acoustic variables involved?In the speech material used for the present perceptual investigations, the variations invocal effort had been induced in a natural way by varying the distance between thespeaker and the person spoken to over a wide range (Andersson, Eriksson andTraunmüller, 1996) and the subjects were asked to rate this distance without anyexplicit mentioning of “vocal effort”.MethodSubjectsThere were three experiments. In the first two, 5 male and 5 female listeners served assubjects. In the third, there were 10 male and 10 female subjects. Most of them werestudents, without known hearing disorders and familiar with Stockholm Swedish. Nosubject participated in more than one of the experiments.

Speech materialThere were five phonated and two whispered versions of the sentence ”Jag tog ettviolett, åtta svarta och sex vita” ‘I took one violet, eight black and six white’ producedby 6 men (mean age 35 years), 6 women (mean age 25 years), four boys and four girls(all 7 years). The sentence had been elicited in response to the question ”Hur mångakort tog du av varje färg?” ‘How many cards of each color did you take?’ by anexperimenter, always the same, whose distance from the speaker was 0.3, 1.5, 7.5,38.5, or 187.5 m for the phonated versions, and 0.3 and 1.5 m for the whispered. Forthe adult speakers, the procedure has been described by Andersson, Eriksson andTraunmüller (1996) and the same procedure was followed when recording thechildren. The speech material has been subjected to various acoustic measurementsamong which the following figure in the present report:1) The overall duration of the whole sentence.2) The mean value of the fundamental frequency over all voiced portions.3) A measure of spectral emphasis, calculated as the excess of the total signal level Lover the ‘level of the first partial’ L 0 , measured after low pass filtering the signal at1.5 F 0 (mean), 36 dB/octave.4) Approximate mean values of F 1 and F 3 , obtained by LPC analysis of theconcatenated voiced portions of each utterance using a rectangular analysis windowwhose length was equal to that of the utterance. For this purpose, the signal wasdown sampled to 10.667, 8.0 and 6.4 kHz for children, women and men, and 8reflection coefficients were used.ProcedureThe utterances were presented to the subjects through headphones in randomizedorder and they had to choose among a number of response alternatives on screen.When they had made their choice, the next stimulus was presented. In experiments 1and 2, the task was to estimate the distance between the speaker and person spoken to(in 25 steps from 0.2 to 490 m). In experiment 1, the stimuli were presented (twice)with the natural variation in level that a listener would experience at a constantdistance from the speaker. In experiment 2, each utterance was presented at twoconstant levels that differed by 6 dB. In experiment 3, the task consisted in estimatingthe age of the listener (in 25 steps from 4 to 75 years) and to give a confidence ratingconcerning the speaker’s sex (in 9 steps from certain female to certain male). Theexperiments were done by Jessika Rundlöf (1996), who also studied the correlationswith the acoustic factors (1) to (3) in experiments 1 and 2, before the formantfrequencies (4) had been measured.Results and discussionVocal effort judgements by distanceThe distance estimates were heavily biased. While the smallest distance, 0.3 m wasoverestimated, the distances from 7.5 to 187.5 m were underestimated in bothexperiments (1 and 2). Therefore, the slopes of the regression lines listed in Table 1 arebelow 1.00. An improved fit is obtained by correlating the distance ratings (in meters)with the modified distance sqrt(distance 2 + 1.5 2 ). The differences between the resultsof the two experiments and between the two levels of presentation in exp. 2 were smallbut significant. The distance ratings could be predicted very well from the acousticfactors (see Table 2) and they can be taken as quite accurate measures of vocal effort,which is indicated by the high correlation between the ratings obtained for eachutterance in the two experiments (2 vs. 1 in Tabel 1).

Table 1. Ratings of communicative distance correlated with spatial distance and witheach other, and ratings of speaker age correlated with chronological age.Exp. nr. Slope rlog 2 (dist) against spatial distance 1 0.58 0.90log 2 (dist) against modified distance 1 0.79 0.93log 2 (dist) against log 2 (dist) 2 vs. 1 0.93 0.993log 2 (age) against chronological age 3 0.97 0.97Table 2. Multiple regression analysis of six acoustic properties (independentvariables) vs. perceived communicative distance, speaker age and sex (dependentvariables). Coefficients indicate unnormalized weights of acoustic propertiesquantified as listed. Question mark: not significantly different from zero (p > 0.05).PerceptDistance Distance Age Confidence rated sexexp. 1 exp. 2Quantification log 2 (dist) log 2 (dist) log 2 (age) Female (1) .. male (2)Set of utterances phonated phonated all adults childrenn 99 99 138 83 55r 2 0.94 0.95 0.88 0.81 0.05Coefficients:F 0 [+1 octave] 2.15 2.06 0.14 ? -0.27 -0.07 ?F 1 [+1 octave] 1.18 1.04 -0.18 ? -0.02 ? 0.35 ?F 3 [+1 octave] -4.53 -4.43 -3.52 -1.75 -0.02 ?L - L 0 [+6 dB] 1.90 1.77 0.14 ? 0.34 -0.16 ?Duration [doubled] -0.08 ? 0.12 ? -0.01 ? -0.16 ? 0.10 ?[Whispered vs. phonated] ------ ------ 0.10 ? 0.06 ? 0.06 ?Age judgementsThe mean age ratings were close to the chronological age of the speakers (see Table 1)and they could be predicted fairly well on the basis of the acoustic factors considered(see Table 2). This is remarkable, since the acoustic factors are affected in a similarway by variation in age as by variation in sex. The weights of the coefficients listed inTable 2 have been obtained by comparing ‘adults’ with ‘children’. They are likely toturn out quite differently in comparisons including only children or only adults ofdifferent age.Sex judgementsThe mean sex ratings agreed with the physiological sex for all utterances of the adultspeakers. While the subjects were less confident in rating the sex of the children, therewere actually only three category confusions in the mean data, but may more in theindividual data For adult speakers, the sex ratings clustered close to the extremes ofthe scale and they could be predicted fairly well from the acoustic data (r = 0.91), butfor children this attempt failed obtrusively (r = 0.24), see Table 2. Since the acousticfactors considered here cover almost all of any ‘static’ spectral differences between theutterances, we have to conclude that the recognition of sex in children must be mainlybased on dynamic and segment specific properties of speech signals. It has beenreported that the number of F 0 -movements per time unit is significantly higher in thespeech of girls than in that of boys (Johansson, 1979), but such variation is restricted

y linguistic factors so that this can hardly be valid when the utterances arelinguistically identical.Reverse analysisSince we are not used to reasoning about speech signals from a perceptual point ofview, the meaning of the figures in Table 2 is not easily grasped. We can, however,reverse the analysis and predict the acoustic quantities on the basis of the perceptual.The result is shown in Table 3. In this table, then, we see the acoustic affects of theparalinguistic variations that were present in the speech material, as defined by thelisteners. This gives us a more familiar picture, whose details for the most part aremore immediately intelligible.Table 3. Multiple regression analysis of perceived qualities (independent variables)vs. five acoustic variables (dependent variables). Coefficients indicate unnormalizedweights of variables quantified as listed. Question mark: not significantly differentfrom zero (p > 0.05).Property Pitch F 1 F 3 Emphasis DurationQuantification log 2 (F 0 ) log 2 (F 1 ) log 2 (F 3 ) L - L 0 log 2 (dur)Unit octave octave octave dBSet of utterances phonated all all phonated alln 99 138 138 99 138r 2 0.90 0.89 0.91 0.82 0.41Coefficients:Sex [male vs. female] -0.46 -0.14 -0.13 0.1 0.00 ?Age [doubled] -0.39 -0.24 -0.24 0.1 ? -0.20Distance (1) [doubled] 0.17 0.14 0.01 1.4 0.07[Whispered vs. phonated] ----- 0.12 0.02 ? ----- -0.11 ?* Men vs. children -1.18 -0.64 -0.65 1.0 -0.49* Women vs. children -0.50 -0.34 -0.37 -0.0 ? -0.41* Men vs. women -0.68 -0.31 -0.28 1.0 -0.06 ?* Boys vs. girls 0.01 ? 0.02 ? 0.00 ? 0.0 ? 0.00 ?* For these subsets, the figures on the other rows are not valid.AcknowledgementsThis research has been supported, in part, by a grant from HSFR within the frame ofthe Swedish language technology programme. I am grateful to Jessika Rundlöf, whohas done all the practical work involved in running these experiments with subjects.ReferencesAndersson A., Eriksson A. and Traunmüller H. 1996. Cries and whispers: Acousticeffects of variations in vocal effort. TMH-QPSR 2/1996, Speech, Music andHearing, Royal Institute of Technology, Stockholm, 127 - 130.Johansson I. 1979. Könsbedömning av förskolebarn på grundval av prosodi.Könsroller i språk 3; FUMS Report Series, no 75, Institutionen för nordiska språk,Uppsala universitet, 75-93.Rundlöf J. 1996. Perceptuella ledtrådar vid auditiv bedömning av avståndet mellantalare och lyssnare. D-uppsats, Institutionen för lingvistik, Stockholms universitet.Traunmüller H. 1997. En tur i fonetikens marker: språkliga och utomspråkligafenomen http://www.ling.su.se/staff/hartmut/tur.htmWilkens H. and Bartel H-H. 1977. Wiedererkennbarkeit der Originallautstärke einesSprechers bei elektroakustischer Wiedergabe. Acustica 37, 45-49.