Formant Frequencies Research Articles

Production of English Vowel Contrasts in Spanish L1 Learners: A Longitudinal Study

The present study undertakes a longitudinal examination of forty postgraduate students, native Spanish speakers, during their first year at a UK university. The research focuses on both individual and collective progress in mastering distinctions within English vowel pairs (/iː/-/ɪ/, /ɪ/-/e/, and /uː/-/ʊ/), with a specific focus on adaptations towards achieving native-like English vowel pronunciation, particularly in terms of vowel quality. Prior research indicates that adult Spanish learners encounter difficulties in mastering the intricate linguistic nuances presented by English. The methodology involved recording Spanish-speaking participants reading a list of words (CVC context) at three different time points over a year. The analysis was based on formant frequencies using Praat, and Euclidean distances were calculated to represent the degree of separation between each pair of vowels. Information about external factors potentially influencing the development of vowel productions among speakers was gathered through a language background questionnaire. The outcomes suggested varying rates of advancement within the group, which could be attributed to the diverse levels of exposure and interaction with native English speakers during their year of study in the UK. These results affirm the learning processes in adult L2 production, emphasizing the critical role played by both the quantity and quality of time in the assimilation of pronunciations to novel L2 segments.

Beyond the average: embracing speaker individuality in the dynamic modeling of the acoustic-articulatory relationship

This paper explores the acoustic-articulatory relationship while considering individual differences in speech production. We aimed to determine whether there is a causal relationship between tongue movements and the contours of the first and second formant frequencies (F 1 and F 2) employing a hierarchical Bayesian continuous-time dynamic model, which allows for a more direct connection between the acoustic and articulatory measured variables and theories involving dynamicity. The results show predictive tendencies for both formants, where the anteroposterior and vertical tongue movements may predict changes in F 1, with rising predicting an increase and retraction a decrease; and with tongue fronting and tongue height inversely predicting F 2. Further, the modeled individual differences showed similar global tendencies, except for the rate of change of F 2. Overall, this study provides valuable insights into the relationship between tongue articulatory variables and formant contours, while accounting for between-speaker variability. The results show predictive tendencies for both formants, where the anteroposterior and vertical tongue movements may predict changes in f1, with rising predicting an increase and retraction a decrease; and with tongue fronting and tongue height inversely predicting f2. Further, the modeled individual differences showed similar global tendencies, however with larger error estimates. Overall, this study provides valuable insights into the relationship between tongue articulatory variables and formant contours, while accounting for between-speaker variability.

Using Formant Characteristics of Russian Vowels and Consonants for User Authentication

The article proposes a method for user authentication based on formant characteristics. A biometric image has been developed consisting of the formant characteristics of 46 sounds of the Russian language (6 vowels, 4 diphthongs and 36 consonants). An authentication system architecture based on formant characteristics and frequency of the leading formant of vowels and consonants is proposed. A Module for extracting the formant characteristics of vowels and consonants has been developed. A block diagram of the Module for extracting the formant characteristics of vowels and consonants and block diagrams of its submodules are presented. The Random Forest algorithm, k-nearest neighbors, logistic regression, multilayer perceptron and Support Vector Machine are combined into a cluster of algorithms. A block diagram of training and testing models based on a cluster of algorithms is given. Models were trained on the basis of algorithms clusters. The results of the experiment were obtained and their analysis was carried out.

The Effect of Phonetic Vowel Spelling Variances on Singers' Performed Vowel

The purpose of this study was to examine the extent to which various phonetic spellings of a single vowel can influence singers' performed vowel, and to explore whether the International Phonetic Alphabet (IPA) may provide an alternative to phonetic spelling in sheet music. I prepared two short, sight-singable melodies of similar range and difficulty; one had vowels written as IPA symbols under the staff, including the /u/ vowel, while the other had the vowels written out phonetically, including two occurrences of the /u/ vowel, spelled in two different ways ("oo" and "ooh"). Each participant (N=41) performed both conditions in a randomized order. I recorded their performances and used the linguistics software Praat to analyze the frequencies of the first and second formants (F1 and F2) for each condition. I found no significant differences in formant frequencies between the conditions. In their exit survey responses, many participants indicated that they recognized a difference in the pronunciation of "oo" and "ooh." Participants also indicated a slight, though not significant, preference for phonetic spelling over IPA. These results suggest that while some singers believe that "oo" and "ooh" should be sung differently, this belief is not reflected in their performance. Results also suggest that IPA is no better at eliciting a specific pronunciation than either phonetic spelling, and is not recommended as a replacement to phonetic spelling in sheet music. I discuss the implications of these findings for choral teachers and composers, and suggest avenues for further research.

Developmental Changes in Acoustic Characteristics of Speech of Estonian Adolescents

The paper introduces the Estonian Adolescent Speech Corpus and explores the developmental changes in speech production based on acoustic characteristics of fundamental frequency (F0), formant frequencies, and speech tempo as a function of age and gender. Age- and gender-related anatomic changes in adolescence have implications for speech acoustics: a sudden drop of F0 at puberty in boys, and an almost gradual decrease of the acoustic vowels space. In parallel with anatomic changes, the development of the speech motor system is manifested as the increase of speaking rate. The analysis of fundamental frequency (F0) shows that in both male and female speakers, the F0 decreases gradually at the age from 9 to 12 years, then in males F0 drops ca by 100 Hz at the age of 12–15 due to puberty voice change, and becomes stable at the age of 15–18; in female speakers, a gradual decrease of F0 continues till the age 18. The formant frequencies of vowels decrease gradually from 10 to 15 years in both genders and the quality of vowels stabilizes at the age of 15–18 years, gender-specific differences emerge at the age of 12–13. Speech rate increases from 4 syllables per second in 9–10 years to 5.1 syllables per second in 14 years and becomes stable between the ages of 15 and 18, gender differences are not significant. The results of the current study can be considered as reference data that are typical for Estonian-speaking individuals aged 9–18 years with normal language development.

On the Alignment of Acoustic and Coupled Mechanic-Acoustic Eigenmodes in Phonation by Supraglottal Duct Variations.

Sound generation in human phonation and the underlying fluid-structure-acoustic interaction that describes the sound production mechanism are not fully understood. A previous experimental study, with a silicone made vocal fold model connected to a straight vocal tract pipe of fixed length, showed that vibroacoustic coupling can cause a deviation in the vocal fold vibration frequency. This occurred when the fundamental frequency of the vocal fold motion was close to the lowest acoustic resonance frequency of the pipe. What is not fully understood is how the vibroacoustic coupling is influenced by a varying vocal tract length. Presuming that this effect is a pure coupling of the acoustical effects, a numerical simulation model is established based on the computation of the mechanical-acoustic eigenvalue. With varying pipe lengths, the lowest acoustic resonance frequency was adjusted in the experiments and so in the simulation setup. In doing so, the evolution of the vocal folds' coupled eigenvalues and eigenmodes is investigated, which confirms the experimental findings. Finally, it was shown that for normal phonation conditions, the mechanical mode is the most efficient vibration pattern whenever the acoustic resonance of the pipe (lowest formant) is far away from the vocal folds' vibration frequency. Whenever the lowest formant is slightly lower than the mechanical vocal fold eigenfrequency, the coupled vocal fold motion pattern at the formant frequency dominates.

Voice Discrimination in Quiet and in Background Noise by Simulated and Real Cochlear Implant Users.

Cochlear implant (CI) users demonstrate poor voice discrimination (VD) in quiet conditions based on the speaker's fundamental frequency (fo) and formant frequencies (i.e., vocal-tract length [VTL]). Our purpose was to examine the effect of background noise at levels that allow good speech recognition thresholds (SRTs) on VD via acoustic CI simulations and CI hearing. Forty-eight normal-hearing (NH) listeners who listened via noise-excited (n = 20) or sinewave (n = 28) vocoders and 10 prelingually deaf CI users (i.e., whose hearing loss began before language acquisition) participated in the study. First, the signal-to-noise ratio (SNR) that yields 70.7% correct SRT was assessed using an adaptive sentence-in-noise test. Next, the CI simulation listeners performed 12 adaptive VDs: six in quiet conditions, two with each cue (fo, VTL, fo + VTL), and six amid speech-shaped noise. The CI participants performed six VDs: one with each cue, in quiet and amid noise. SNR at VD testing was 5 dB higher than the individual's SRT in noise (SRTn +5 dB). Results showed the following: (a) Better VD was achieved via the noise-excited than the sinewave vocoder, with the noise-excited vocoder better mimicking CI VD; (b) background noise had a limited negative effect on VD, only for the CI simulation listeners; and (c) there was a significant association between SNR at testing and VTL VD only for the CI simulation listeners. For NH listeners who listen to CI simulations, noise that allows good SRT can nevertheless impede VD, probably because VD depends more on bottom-up sensory processing. Conversely, for prelingually deaf CI users, noise that allows good SRT hardly affects VD, suggesting that they rely strongly on bottom-up processing for both VD and speech recognition.

Altered neural encoding of vowels in noise does not affect behavioral vowel discrimination in gerbils with age-related hearing loss.

Understanding speech in a noisy environment, as opposed to speech in quiet, becomes increasingly more difficult with increasing age. Using the quiet-aged gerbil, we studied the effects of aging on speech-in-noise processing. Specifically, behavioral vowel discrimination and the encoding of these vowels by single auditory-nerve fibers were compared, to elucidate some of the underlying mechanisms of age-related speech-in-noise perception deficits. Young-adult and quiet-aged Mongolian gerbils, of either sex, were trained to discriminate a deviant naturally-spoken vowel in a sequence of vowel standards against a speech-like background noise. In addition, we recorded responses from single auditory-nerve fibers of young-adult and quiet-aged gerbils while presenting the same speech stimuli. Behavioral vowel discrimination was not significantly affected by aging. For both young-adult and quiet-aged gerbils, the behavioral discrimination between /eː/ and /iː/ was more difficult to make than /eː/ vs. /aː/ or /iː/ vs. /aː/, as evidenced by longer response times and lower d' values. In young-adults, spike timing-based vowel discrimination agreed with the behavioral vowel discrimination, while in quiet-aged gerbils it did not. Paradoxically, discrimination between vowels based on temporal responses was enhanced in aged gerbils for all vowel comparisons. Representation schemes, based on the spectrum of the inter-spike interval histogram, revealed stronger encoding of both the fundamental and the lower formant frequencies in fibers of quiet-aged gerbils, but no qualitative changes in vowel encoding. Elevated thresholds in combination with a fixed stimulus level, i.e., lower sensation levels of the stimuli for old individuals, can explain the enhanced temporal coding of the vowels in noise. These results suggest that the altered auditory-nerve discrimination metrics in old gerbils may mask age-related deterioration in the central (auditory) system to the extent that behavioral vowel discrimination matches that of the young adults.

Adapted Weighted Linear Prediction with Attenuated Main Excitation for formant frequency estimation in high-pitched singing

This paper aims to show how to improve the accuracy of formant frequency estimation in the singing voice of a lyric soprano. Conventional methods of formant frequency estimation may not accurately capture the formant frequencies of the singing voice, particularly in the highest pitch range of a lyric soprano, where the lowest formants are biased by the pitch harmonics. To address this issue, the study proposes adapting the Weighted Linear Prediction with Attenuated Main Excitation (WLP-AME) method for formant frequency estimation. Specific methods for glottal closure instant estimation were required due to differences in glottal closure patterns between speech and singing. The study evaluates the accuracy of the proposed method by comparing its performance with the LPC method through different pitch series arranged in an ascending musical scale. The results indicated that the adapted WLP-AME method consistently outperformed the LPC method in estimating formant frequencies of vowels sung by a lyric soprano. In addition, by estimating the formant frequencies of a synthetic /i/ vowel sung by a soprano singer at the musical note E5, the study showed that the adapted WLP-AME method provided formant frequency values closer to the correct values than those estimated by the LPC method. In general, these results suggest parameter values of AME function that optimize its performance, which can have applications in fields such as singing and medicine.

Formant and Voice Source Characteristics of Vowels in Chinese National Singing and Bel Canto. A Pilot Study

There have been numerous reports on the acoustic characteristics of singers' vowel articulation and phonation, and these studies cover many phonetic dimensions, such as fundamental frequency (F0), intensity, formant frequency, and voice quality. Taking the three representative vowels (/a/, /i/, /u/) in Chinese National Singing and Bel Canto as the research object, the present study investigates the differences and associations in vowel articulation and phonation between Chinese National Singing and Bel Canto using acoustic measures, for example, F0, formant frequency, long-term average spectrum (LTAS). The relationship between F0 and formant indicates that F1 is proportional to F0, in which the female has a significant variation in vowel /a/. Compared with the male, the formant structure of the female singing voice differs significantly from that of the speech voice. Regarding the relationship between intensity and formant, LTAS shows that the Chinese National Singing tenor and Bel Canto baritone have the singer's formant cluster when singing vowels, while the two sopranos do not. The systematic changes of formant frequencies with voice source are observed. (i) F1 of the female vowel /a/ has undergone a significant tuning change in the register transition, reflecting the characteristics of singing genres. (ii) Female singers utilize the intrinsic pitch of vowels when adopting the register transition strategy. This finding can be assumed to facilitate understanding the theory of intrinsic vowel pitch and revise Sundberg's hypothesis that F1 rises with F0. A non-linear relationship exists between F1 and F0, which adds to the non-linear interaction of the formant and vocal source. (iii) The singer's formant is affected by voice classification, gender, and singing genres.

Assessment of Tracks of Resonance Frequencies of the Vocal Tract

A new method for estimating formant frequency tracks of the vocal tract for arbitrary speech segments is proposed. The method uses the ratio of two Fourier transforms of a speech signal with special exponential-type windows depending on some parameter. This ratio is used for specific points in time and is considered as a function of frequency and parameter. By analyzing, for several parameter values, the distribution of minimum points (in terms of frequency) for the phase of this ratio and/or a similar distribution of extreme points for its amplitude, it is possible to estimate formant frequencies from the peaks of these distributions. A mathematical study is presented that substantiates this approach. A series of numerical experiments were carried out on the processing of synthetic and real speech signals, which confirmed the performance capabilities of the proposed formant evaluation method. In particular, in experiments with synthesized vowels, it was found that the error in estimating their resonance frequencies is small and stable with respect to additive noise up to a signal-to-noise ratio of 5 dB. For real speech, the method makes it possible to calculate the formant frequency tracks for both sounds with vocal excitation and for voiceless fricatives, aspirated plosives, and whispered speech.

High and Wide: An In Silico Investigation of Frequency, Intensity, and Vibrato Effects on Widely Applied Acoustic Voice Perturbation and Noise Measures

This in silico study explored the effects of a wide range of fundamental frequency (fo), source-spectrum tilt (SST), and vibrato extent (VE) on commonly used frequency and amplitude perturbation and noise measures. Using 53 synthesizedtones produced in Madde, the effects of stepwise increases in fo, intensity (modeled by decreasing SST), and VE on the PRAAT parameters jitter % (local), relative average perturbation (RAP) %, shimmer % (local), amplitude perturbation quotient 3 (APQ3) %, and harmonics-to-noise ratio (HNR) dB were investigated. A secondary experiment was conducted to determine whether any fo effects on jitter, RAP, shimmer, APQ3, and HNR were stable. A total of 10 sinewaves were synthesizedin Sopran from 100 to 1000Hz using formant frequencies for /a/, /i/, and /u/-like vowels, respectively. All effects were statistically assessed with Kendall's tau-b and partial correlation. Increasing fo resulted in an overall increase in jitter, RAP, shimmer, and APQ3 values, respectively (P<0.01). Oscillations of the data across the explored fo range were observed in all measurement outputs. In the Sopran tests, the oscillatory pattern seen in the Madde fo condition remained and showed differences between vowel conditions. Increasing intensity (decreasing SST) led to reduced pitch and amplitude perturbation and HNR (P<0.05). Increasing VE led to lower HNR and an almost linear increase of all other measures (P<0.05). These novel data offer a controlled demonstration for the behavior of jitter (local) %, RAP %, shimmer (local) %, APQ3 %, and HNR (dB) when varying fo, SST, and VE in synthesizedtones. Since humans will vary in all of these aspects in spoken language and vowel phonation, researchers should take potential resonance-harmonics type effects into account when comparing intersubject or preintervention and postintervention data using these measures.

Vocal tract shape variation contributes to individual vocal identity in African penguins.

Variation in formant frequencies has been shown to affect social interactions and sexual competition in a range of avian species. Yet, the anatomical bases of this variation are poorly understood. Here, we investigated the morphological correlates of formants production in the vocal apparatus of African penguins. We modelled the geometry of the supra-syringeal vocal tract of 20 specimens to generate a population of virtual vocal tracts with varying dimensions. We then estimated the acoustic response of these virtual vocal tracts and extracted the centre frequency of the first four predicted formants. We demonstrate that: (i) variation in length and cross-sectional area of vocal tracts strongly affects the formant pattern, (ii) the tracheal region determines most of this variation, and (iii) the skeletal size of penguins does not correlate with the trachea length and consequently has relatively little effect on formants. We conclude that in African penguins, while the variation in vocal tract geometry generates variation in resonant frequencies supporting the discrimination of conspecifics, such variation does not provide information on the emitter's body size. Overall, our findings advance our understanding of the role of formant frequencies in bird vocal communication.

VSpace: A browser-based vowel synthesiser

Two-formant representation of the universal vowel space is a foundational model in phonetics (Fant &amp; Risberg 1963; Traunmüller &amp; Lacerda 1983), but tools for rapid synthesis of vowel sounds corresponding to points in the vowel space are limited. Stand-alone applications such as the Formant Synthesizer Demo (Beskow, 2000) provide this functionality, and rich tools for formant synthesis are available in Praat (Boersma and Weenink, 2023), Matlab (Rabiner et al., 2023) and other platforms, but these tools are not universally accessible, while web-based speech synthesis tools (e.g., Thapen, 2017) do not typically allow systematic manipulation or quantification of key acoustic parameters. VSpace is a browser-based formant synthesizer developed using the Tone.js Web Audio framework. A universal vowel space is represented as a trapezoid scaled to typical male, female or child speaker formant ranges. Clicking on any point generates a vowel sound corresponding to the first and second formant frequencies selected, synthesized with typical F3 and F4 frequencies excited by a selectable source signal. IPA symbols corresponding to typical formant frequencies for language-specific vowel phonemes may be superimposed on the vowel space. Key synthesis parameters are configurable through the web interface to allow exploration of the acoustic consequences for vowel perception.

Acoustic and durational correlates of diphthong contrasts in Nafsan

The phonetic realization of diphthongs, vowels with dynamic productions involving two targets and often described as inherently long, is under-studied cross-linguistically (e.g., Petersen, 2018), including within many well-documented languages. Nafsan, an Oceanic language spoken by around 6000 people on Efate island in Vanuatu, has a vowel inventory with monophthongs of five qualities, all with a length contrast (Billington et al., 2021), and at least six contrastive closing diphthongs (Thieberger, 2006). These include /ei/ and /oi/, and two pairs in which the primary difference is viewed as the height of the second target: /ai/ and /ae/, and /au/ and /ao/. However, there are indications that duration may be an important correlate in these pairs. This presentation reports on a study of the six closing diphthongs based on data collected with six Nafsan speakers in Erakor village, using a wordlist of mostly monosyllabic words with diphthongs in both open syllables and syllables closed with a coronal consonant, produced in an utterance-medial frame. Results show that, in addition to differences in second formant frequency, /ae/ and /ao/ are significantly longer than /ai/ and /au/, raising questions about whether the contrast is best interpreted as a length contrast similar to that found among monophthongs.

The vowel inventory of Nakanamanga

Nakanamanga is an Oceanic language spoken by approximately 10,000 speakers in central Vanuatu (Lynch and Crowley, 2001), including northern Efate island and Nguna and other small islands to the north. Previous work on Nakanamanga indicates that it has five distinctive vowel qualities (/i,e,a,o,u/), as is typical of Oceanic languages, and some evidence of long vowels (Schütz, 1969). However, whether vowel length is contrastive remains unclear, and there are suggestions that vowel length exhibits complex relationships with consonantal and prosodic patterns (Schütz, 1969; McClintock, 1991; Schmidt, 2023). We present findings of a pilot study targeting vowel length in Nakanamanga, based on phonological evidence and acoustic phonetic data. A wordlist consisting of words of CVCV structures was designed after consultation with a native speaker, and recorded with the speaker in Mere-Sauwia village on Nguna. Data was processed and analysed using Praat, EMU-SDMS and R (Boersma and Weenink, 2023; Winkelmann et al., 2017; R Core Team, 2023). Results for vowel duration and first and second formant frequency at vowel midpoints provide strong evidence that Nakanamanga has ten distinct vowels, with a length contrast for all five vowel qualities. Findings lay the groundwork for larger-scale investigations of the phonetics and phonology of Nakanamanga.

A cross-dialect study of vowel production in Parkinson’s disease

The impact of dysarthria on vowel formant frequencies is well established. Additionally, it is understood that speaker dialects significantly influence formant frequencies. However, the specific interaction between dysarthria and speaker dialect remains a relatively unexplored area in research. This knowledge gap may hinder the generalizability of dysarthria findings from one regional dialect to speakers of other dialects. As an initial step in this research line, the current study investigates the interaction between regional dialects and dysarthria in Parkinson’s disease (PD) on vowel production. To do this, our study analyzes acoustic and kinematic data from speakers with and without dysarthria, representing Midwestern and Southern United States dialects. We examine both single-word repetitions and passage-reading contexts, recognizing that there may be a significant task effect. The study includes 50 speakers, with 24 speakers (10 PD, 14 control) from the Southern Dialect (collected in Louisiana and Florida) and 26 speakers (13 PD, 13 control) from the Upper Midwest dialect (collected in Wisconsin). The findings will shed light on the interaction between regional dialects and dysarthria, offering valuable insights for speech rehabilitation and understanding speech variations across different populations.

Kinematic redundancies in /u/ production with and without dysarthria

The speech sensorimotor control system exploits kinematic redundancies: various articulatory degrees of freedom can exhibit trading relationships in service of a speech goal. These redundancies affect movements within and across articulators, resulting in multiple “motor equivalent” patterns that may lead to perceptually equivalent phonemes. One classic example of this redundancy is the purported trading relationship between the tongue and lips in controlling the frequency of the second formant (F2). For the acoustic goal of achieving a relatively low F2 frequency in the vowel /u/, neurotypical talkers may exhibit trade-offs in tongue dorsum and lip position to allow motor adaptability while achieving the acoustic goal. The current work examines speech kinematic and acoustic data from many talkers with and without dysarthria during connected speech to further evaluate the proposition that tongue-lip movement trade-offs allow relatively adaptable articulatory movement in service of a relatively stable acoustic goal during /u/. It is hypothesized that idiosyncrasies in the kinematic form of tongue-lip trade-offs may reflect speaker-specific articulatory-acoustic mappings and that dysarthria may compromise the use of kinematic redundancies, particularly when articulation is severely impaired. Discussion will focus on how methodological issues, particularly kinematic and acoustic normalization, influence the findings.

Didjeridu acoustics: A review

The didjeridu is the principal musical instrument of the world’s oldest continuous culture and its sound is an acoustic icon of Australia. This lip-valve instrument usually produces a single, sustained, low note. The musical interest comes from rhythmic changes in timbre, including those associated with ‘circular breathing’, wherein exhalation from lungs to instrument with raised velum is alternated with expulsion of air from the inflated cheeks while air is quickly inhaled through the nose, with the velum lowered. This paper reviews research from our lab. Measurements of the acoustic impedance spectrum in the mouth during playing show that impedance peaks produce antiformants or minima in the output sound spectral envelope. The instrument’s slight flare and irregular bore geometry produce resonances that do not fall in harmonic ratios. Instruments judged good by players have particularly weak resonances in the formant frequency region so that the vocal tract impedance peaks can dominate the sound spectrum more easily. In one technique, players phonate at frequencies above that of the instrument, producing complicated heterodyne components. Lips are low Q oscillators and, as in other lip-valve instruments, the energetics of lip oscillation depends on the phase difference between the lips’ longitudinal and lateral motion.

Identification training adapted to the learner’s vowel space aids in improving native Japanese speakers’ pronunciation of American English vowels

Native speakers of Japanese learning English as a foreign language often have difficulty pronouncing certain American English (AE) vowels, such as the mid vowels /ae/, /ɑ/, / ^/, /ɔ/, and /ɚ/, which typically are assimilated to native vowel categories. It was shown that vowel identification training which was adapted to the learner’s vowel space could aid in improving the native Japanese speakers’ pronunciation of a set of 12 AE vowels that included the 5 more difficult mid vowels. Estimates of the vocal-tract length (VTL) for 53 learners were based upon the central tendency and range of the four lowest formant frequencies observed in their recordings of five short statements in the Japanese language. Having thus characterized the individual vowel spaces of 53 learners, 33 were placed in a “longer-VTL” group while the remaining 20 were placed in a “shorter-VTL” group. Those in the “longer-VTL” group were given periodic identification training using examples of 12 American English monophthongs in a consonant-vowel-consonant (CVC) context that sounded as if a male AE speaker with similar VTL had uttered them. The “shorter-VTL” learners heard training examples that sounded as if the CVCs were uttered by a female AE speaker with similarly short VTL.