1aPP – The Role of Talker/Vowel Change in Consonant Recognition with Hearing Loss

Ali Abavisani – aliabavi@illinois.edu
Jont B. Allen – jontalle@illinois.edu
Dept. of Electrical and Computer Engineering
University of Illinois at Urbana-Champaign
405 N Mathews Ave
Urbana, IL, 61801

Popular version of paper 1aPP
Presented Monday, May 13, 2019
177th ASA Meeting, Louisville, KY

Hearing loss can have serious impact on social life of individuals experiencing it. The effect of hearing loss becomes more complicated in environments such as restaurants, where the background noise is similar to speech. Although hearing aids in various designs, intend to address these issues, users complain about hearing aids performance in social situations, where they are mostly needed. Part of this problem refers to the nature of hearing aids, which do not use speech as part of design and fitting process. If we somehow incorporate speech sounds in real life conditions into the fitting process of hearing aids, it may be possible to address most of the shortcomings that irritates the users.

There have been many studies on the features that are important in identification of speech sounds such as isolated consonant + vowel (CV) phones (i.e., meaningless speech sound). Most of these studies ran experiments on normal hearing listeners, to identify the effects of different speech features in correct recognition. It turned out that manipulation of speech sounds, such as replacing a vowel, or amplifying/attenuating certain parts of sound in time-frequency domain, leads to identification of new speech sounds by the normal hearing listeners. One goal of current study is to investigate whether there are similar responses to such manipulations from listeners who have hearing loss.

We designed a speech-based test that may be utilized by audiologists to determine susceptible speech phones for each individual with hearing loss. The design includes a perceptual measure that corresponds to speech understanding in background noise, where the noise is similar to speech. The perceptual measure identifies the noise level in which the speech sound is recognizable by an average normal hearing listener, at least with 90% accuracy. The speech sounds within the test include combinations of 14 consonants {p, t, k, f, s, S, b, d, g, v, z, Z, m, n} and four vowels {A, ae, I, E}, to cover different features that are present in speech. All the test sounds have pre-evaluated to make sure they are recognizable by normal hearing listeners in the noise conditions of the experiments. Two sets of sounds named T$_1$ and T$_2$ having same consonant-vowel combinations of sounds but different talkers, had been presented to the listeners at their most comfortable level of hearing (not depending to their specific hearing loss). The two speech sets had distinct perceptual measure. When two sounds with similar perceptual measure, and with the same consonant but different vowel are presented to a listener with hearing loss, their response can show us how their particular hearing function, may cause errors in understanding this particular speech sound, and why this function led to recognition of a specific sound instead of the presented speech. Also, presenting sounds from the two sets constitute the means to compare the role of perceptual measure (which is based on normal hearing listeners), on listeners with hearing loss. When the recognition score for a particular listener increases as the result of a change in presented speech sounds, it is an indication on how the fitting process of hearing aid should follow, regarding that particular (listener, speech sound) pair.

While the study shows that improvement or degradation of the speech sounds are listener dependent, on average 85% of sounds are improved when we replaced the CV with same CV but with a better perceptual measure. Additionally, using CVs with similar perceptual measure, on average 28% of CVs are improved when we replaced the vowel with vowel {A}, 28% of CVs are improved when we replaced the vowel with vowel {E}, 25% of CVs are improved when we replaced the vowel with vowel {ae}, and 19% of CVs are improved when we replaced the vowel with vowel {I}.

The confusion pattern in each case, provides insight on how these changes affect the phone recognition in each ear. We propose to prescribe hearing aid amplification tailored to individual ears, based on the confusion pattern, the response from change in perceptual measure, and the response from change in vowel.

These tests are directed at the fine-tuning of hearing aid insertion gain, with the ultimate goal of improving speech perception, and to precisely identify when and for what consonants the ear with hearing loss needs treatment to enhance speech recognition.

3pSC87 – What the f***? Making sense of expletives in The Wire

Erica Gold – e.gold@hud.ac.uk
Dan McIntyre – d.mcintyre@hud.ac.uk

University of Huddersfield
Queensgate
Huddersfield, HD1 3DH
United Kingdom

Popular version of 3pSC87 – What the f***: An acoustic-pragmatic analysis of meaning in The Wire
Presented Wednesday afternoon, November 30, 2016
172nd ASA Meeting, Honolulu
Click here to read the abstract

The Wire - expletives

In Season one of HBO’s acclaimed crime drama The Wire, Detectives Jimmy McNulty and ‘Bunk’ Moreland are investigating old homicide cases, including the murder of a young woman shot dead in her apartment. McNulty and Bunk visit the scene of the crime to try and figure out exactly how the woman was killed. What makes the scene unusual dramatically is that, engrossed in their investigation, the two detectives communicate with each other using only the word, “fuck” and its variants (e.g. motherfucker, fuckity fuck, etc.). Somehow, using only this vocabulary, McNulty and Bunk are able to communicate in a meaningful way. The scene is absorbing, engaging and even funny, and it leads to a fascinating question for linguists: how is the viewer able to understand what McNulty and Bunk mean when they communicate using such a restricted set of words?

bunk mcnulty

To investigate this, we first looked at what other linguists have discovered about the word fuck. What is clear is that it’s a hugely versatile word that can be used to express a range of attitudes and emotions. On the basis of this research, we came up with a classification scheme which we then used to categorise all the variants of fuck in the scene. Some seemed to convey disbelief and some were used as insults. Some indicated surprise or realization while others functioned to intensify the following word. And some were idiomatic set phrases (e.g. Fuckin’ A!). Our next step was to see whether there was anything in the acoustic properties of the characters’ speech that would allow us to explain why we interpreted the fucks in the way that we did.

The entire conversation between Bunk and McNulty lasts around three minutes and contains a total of 37 fuck productions (i.e. variations of fuck). Due to the variation in the fucks produced, the one clear and consistent segment for each word was the <u> in fuck. Consequently, this became the focus of our study. The <u> in fuck is the same sound you find in the word strut or duck and is represented as /ᴧ/ in the International Phonetic Alphabet. When analysing vowel sounds, such as <u>, we can look at a number of aspects of its production.

In this study, we looked at the quality of the vowel by measuring the first three formants. In phonetics, the term formant refers to acoustic resonances of sound in the vocal tract. The first two formants can tell us if the production sounds more like, “fuck” rather than, “feck” or “fack,” and the third formant gives us information about the voice quality. We also looked at the duration of the <u> being produced, “fuuuuuck” versus “ fuck.”

After measuring each instance, we ran statistical tests to see if there was any relationship between the way in which it was said, and how we categorised its range of meanings. Our results showed that if we accounted for the differences in the vocal tract shapes of the actors playing Bunk and McNulty, the quality of the vowels are relatively consistent. That is, we get a lot of <u> sounds, rather than “eh,” “oo” or “ih.”

The productions of fucks that were associated with the category of realization were found to be very similar to those associated with disbelief. However, disbelief and realization did contrast with those that were used as insults, idiomatic phrases, or functional words. Therefore, it may be more appropriate to classify the meaning into fewer categories – those that signify disbelief or realization, and those that are idiomatic, insults, or functional. It is important to remember, however, that the latter group of three meanings are represented by fewer examples in the scene. Our initial results show that these two broad groups may be distinguished through the length of the vowel – short <u> is more associated with an insult, function, or idiomatic use rather than disbelief or surprise (for which the vowel tends to be longer). In the future, we would also like to analyse the intonation of the productions. See if you can hear the difference between these samples:

Example 1: realization/surprise

Example 2: general expletive which falls under the functional/idiomatic/insult category

Our results shed new light on what for linguists is an old problem: how do we make sense of what people say when speakers so very rarely say exactly what they mean? Experts in pragmatics (the study of how meaning is affected by context) have suggested that we infer meaning when people break conversational norms. In the example from The Wire, it’s clear that the characters are breaking normal communicative conventions. But pragmatic methods of analysis don’t get us very far in explaining how we are able to infer such a range of meaning from such limited vocabulary. Our results confirm that the answer to this question is that meaning is not just conveyed at the lexical and pragmatic level, but at the phonetic level too. It’s not just what we say that’s important, it’s how we fucking say it!

*all photos are from HBO.com

1aNS4 – Musical mind control: Human speech takes on characteristics of background music

Ryan Podlubny – ryan.podlubny@pg.canterbury.ac.nz
Department of Linguistics, University of Canterbury
20 Kirkwood Avenue, Upper Riccarton
Christchurch, NZ, 8041

Popular version of paper 1aNS4, “Musical mind control: Acoustic convergence to background music in speech production.”
Presented Monday morning, November 28, 2016
172nd ASA Meeting, Honolulu

People often adjust their speech to resemble that of their conversation partners – a phenomenon known as speech convergence. Broadly defined, convergence describes automatic synchronization to some external source, much like running to the beat of music playing at the gym without intentionally choosing to do so. Through a variety of studies a general trend has emerged where we find people automatically synchronizing to various aspects of their environment1,2,3. With specific regard to language use, convergence effects have also been observed in many linguistic domains such as sentence-formation4, word-formation5, and vowel production6 (where differences in vowel production are well associated with perceived accentedness7,8). This prevalence in linguistics raises many interesting questions about the extent to which speakers converge. This research uses a speech-in-noise paradigm to explore whether or not speakers also converge to non-linguistic signals in the environment: Specifically, will a speaker’s rhythm, pitch, or intensity (which is closely related to loudness) be influenced by fluctuations in background music such that the speech echoes specific characteristics of that background music (for example, if the tempo of background music slows down, will that influence those listening to unconsciously decrease their speech rate)?

In this experiment participants read passages aloud while hearing music through headphones. Background music was composed by the experimenter to be relatively stable with regard to pitch, tempo/rhythm, and intensity, so we could manipulate and test only one of these dimensions at a time, within each test-condition. We imposed these manipulations gradually and consistently toward a target, which can be seen in Figure 1, and would similarly return to the level at which they started after reaching that target. We played the participants music with no experimental changes in between all manipulated sessions. (Examples of what participants heard in headphones are available as sound- files 1 and 2)

podlubny_fig1

Fig. 1: Using software designed for digital signal processing (analyzing and altering sound), manipulations were applied in a linear fashion (in a straight line) toward a target – this can be seen above as the blue line, which first rises and then falls. NOTE: After manipulations reach their target (the target is seen above as a dashed, vertical red line), the degree of manipulation would then return to the level at which it started in a similar linear fashion. Graphic captured while using Praat 9 to increase and then decrease the perceived loudness of the background music.

Data from 15 native speakers of New Zealand English were analyzed using statistical tests that allow effects to vary somewhat for each participant where we observed significant convergence in both the pitch and intensity conditions. Analysis of the Tempo condition, however, has not yet been conducted. Interestingly, these effects appear to differ systematically based on a person’s previous musical training. While non-musicians demonstrate the predicted effect and follow the manipulations, musicians appear to invert the effect and reliably alter aspects of their pitch and intensity in the opposite direction of the manipulation (see Figure 2). Sociolinguistic research indicates that under certain conditions speakers will emphasize characteristics of their speech to distinguish themselves socially from conversation partners or groups, as opposed to converging with them6. It seems plausible then that, given a relatively heightened ability to recognize low-level variations of sound, musicians may on some cognitive level be more aware of the variation in their sound environment, and as a result similarly resist the more typical effect. However, more work is required to better understand this phenomenon.

podlubny_fig2

Fig. 2: The above plots measure pitch on the y-axis (up and down on the left edge), and indicate the portions of background music that have been manipulated on the x- axis (across the bottom). The blue lines show that speakers generally lower their pitch as an un-manipulated condition progresses. However the red lines show that when global pitch is lowered during a test-condition, such lowering is relatively more dramatic for non-musicians (left plot) and that the effect is reversed by those with musical training (right plot). NOTE: A follow-up model further accounts for the relatedness of Pitch and Intensity and shows much the same effect.

This work indicates that speakers are not only influenced by human speech partners in production, but also, to some degree, by noise within the immediate speech environment, which suggests that environmental noise may constantly be influencing certain aspects of our speech production in very specific and predictable ways. Human listeners are rather talented when it comes to recognizing subtle cues in speech10, especially compared to computers and algorithms that can’t  yet match this ability. Some language scientists argue these changes in speech occur to make understanding easier for those listening11. That is why work like this is likely to resonate in both academia and the private sector, as a better understanding of how speech will change in different environments contributes to the development of more effective aids for the hearing impaired, as well as improvements to many devices used in global communications. 

Sound-file 1.
An example of what participants heard as a control condition (no experimental manipulation) in between test-conditions. 

Sound-file 2.
An example of what participants heard as a test condition (Pitch manipulation, which drops 200 cents/one full step).

References

1.  Hill, A. R., Adams, J. M., Parker, B. E., & Rochester, D. F. (1988). Short-term entrainment of ventilation to the walking cycle in humans. Journal of Applied Physiology, 65(2), 570-578.
2. Will, U., & Berg, E. (2007). Brain wave synchronization and entrainment to periodic acoustic stimuli. Neuroscience letters, 424(1), 55-60.
3.  McClintock, M. K. (1971). Menstrual synchrony and suppression. Nature, Vol 229, 244-245.
4.  Branigan, H. P., Pickering, M. J., McLean, J. F., & Cleland, A. A. (2007). Syntactic alignment and participant role in dialogue. Cognition, 104(2), 163-197.
5.  Beckner, C., Rácz, P., Hay, J., Brandstetter, J., & Bartneck, C. (2015). Participants Conform to Humans but Not to Humanoid
Robots in an English Past Tense Formation Task. Journal of Language and Social Psychology, 0261927X15584682.
Retreived from: http://jls.sagepub.com.ezproxy.canterbury.ac.nz/content/early/2015/05/06/0261927X15584682.
6.  Babel, M. (2012). Evidence for phonetic and social selectivity in spontaneous phonetic imitation. Journal of Phonetics, 40(1), 177-189.
7.  Major, R. C. (1987). English voiceless stop production by speakers of Brazilian Portuguese. Journal of Phonetics, 15, 197—
202.
8.  Rekart, D. M. (1985) Evaluation of foreign accent using synthetic speech. Ph.D. dissertation, the Lousiana State University.
9.  Boersma, P., & Weenink, D. (2014). Praat: Doing phonetics by computer (Version 5.4.04) [Computer program]. Retrieved
from www.praat.org.
10.  Hay, J., Podlubny, R., Drager, K., & McAuliffe, M. (under review). Car-talk: Location-specific speech production and
perception.
11.  Lane, H., & Tranel, B. (1971). The Lombard sign and the role of hearing in speech. Journal of Speech, Language, and
Hearing Research, 14(4), 677-709.

4pMU4 – How Well Can a Human Mimic the Sound of a Trumpet?

Ingo R. Titze – ingo.titze@utah.edu

University of Utah
201 Presidents Cir
Salt Lake City, UT

Popular version of paper 4pMU4 “How well can a human mimic the sound of a trumpet?”
Presented Thursday May 26, 2:00 pm, Solitude room
171st ASA Meeting Salt Lake City

Man-made musical instruments are sometimes designed or played to mimic the human voice, and likewise vocalists try to mimic the sounds of man-made instruments.  If flutes and strings accompany a singer, a “brassy” voice is likely to produce mismatches in timbre (tone color or sound quality).  Likewise, a “fluty” voice may not be ideal for a brass accompaniment.  Thus, singers are looking for ways to color their voice with variable timbre.

Acoustically, brass instruments are close cousins of the human voice.  It was discovered prehistorically that sending sound over long distances (to locate, be located, or warn of danger) is made easier when a vibrating sound source is connected to a horn.  It is not known which came first – blowing hollow animal horns or sea shells with pursed and vibrating lips, or cupping the hands to extend the airway for vocalization. In both cases, however, airflow-induced vibration of soft tissue (vocal folds or lips) is enhanced by a tube that resonates the frequencies and radiates them (sends them out) to the listener.

Around 1840, theatrical singing by males went through a revolution.  Men wanted to portray more masculinity and raw emotion with vocal timbre. “Do di Petto”, which is Italien for “C  in chest voice” was introduced by operatic tenor Gilbert Duprez in 1837, which soon became a phenomenon.  A heroic voice in opera took on more of a brass-like quality than a flute-like quality.  Similarly, in the early to mid- twentieth century (1920-1950), female singers were driven by the desire to sing with a richer timbre, one that matched brass and percussion instruments rather than strings or flutes.  Ethel Merman became an icon in this revolution. This led to the theatre belt sound produced by females today, which has much in common with a trumpet sound.

Titze_Fig1_Merman

Fig 1. Mouth opening to head-size ratio for Ethel Merman and corresponding frequency spectrum for the sound “aw” with a fundamental frequency fo (pitch) at 547 Hz and a second harmonic frequency 2 fo at 1094 Hz.

The length of an uncoiled trumpet horn is about 2 meters (including the full length of the valves), whereas the length of a human airway above the glottis (the space between the vocal cords) is only about 17 cm (Fig. 2). The vibrating lips and the vibrating vocal cords can produce similar pitch ranges, but the resonators have vastly different natural frequencies due to the more than 10:1 ratio in airway length.  So, we ask, how can the voice produce a brass-like timbre in a “call” or “belt”?

One structural similarity between the human instrument and the brass instrument is the shape of the airway directly above the glottis, a short and narrow tube formed by the epiglottis.  It corresponds to the mouthpiece of brass instruments.  This mouthpiece plays a major role in shaping the sound quality.  A second structural similarity is created when a singer uses a wide mouth opening, simulating the bell of the trumpet.  With these two structural similarities, the spectrum of tones produced by the two instruments can be quite similar, despite the huge difference in the overall length of the instrument.

Titze_Fig2_airway_ trumpet

Fig 2. Human airway and trumpet (not drawn to scale).

Acoustically, the call or belt-like quality is achieved by strengthening the second harmonic frequency 2fo  in relation to the fundamental frequency fo.  In the human instrument, this can be done by choosing a bright vowel like /ᴂ/ that puts an airway resonance near the second harmonic.  The fundamental frequency will then have significantly less energy than the second harmonic.

Why does that resonance adjustment produce a brass-like timbre?  To understand this, we first recognize that, in brass-instrument playing, the tones produced by the lips are entrained (synchronized) to the resonance frequencies of the tube.  Thus, the tones heard from the trumpet are the resonance tones. These resonance tones form a harmonic series, but the fundamental tone in this series is missing.  It is known as the pedal tone.  Thus, by design, the trumpet has a strong second harmonic frequency with a missing fundamental frequency.

Perceptually, an imaginary fundamental frequency may be produced by our auditory system when a series of higher harmonics (equally spaced overtones) is heard.  Thus, the fundamental (pedal tone) may be perceptually present to some degree, but the highly dominant second harmonic determines the note that is played.

In belting and loud calling, the fundamental is not eliminated, but suppressed relative to the second harmonic.  The timbre of belt is related to the timbre of a trumpet due to this lack of energy in the fundamental frequency.  There is a limit, however, in how high the pitch can be raised with this timbre.  As pitch goes up, the first resonance of the airway has to be raised higher and higher to maintain the strong second harmonic.  This requires ever more mouth opening, literally creating a trumpet bell (Fig. 3).

Titze_Fig3_Menzel

Fig 3. Mouth opening to head-size ratio for Idina Menzel and corresponding frequency spectrum for a belt sound with a fundamental frequency (pitch) at 545 Hz.

Note the strong second harmonic frequency 2fo in the spectrum of frequencies produced by Idina Menzel, a current musical theatre singer.

One final comment about the perceived pitch of a belt sound is in order.  Pitch perception is not only related to the fundamental frequency, but the entire spectrum of frequencies.  The strong second harmonic influences pitch perception. The belt timbre on a D5 (587 Hz) results in a higher pitch perception for most people than a classical soprano sound on the same note. This adds to the excitement of the sound.

1pSC26 – Acoustics and Perception of Charisma in Bilingual English-Spanish

Rosario Signorello – rsignorello@ucla.edu
Department of Head and Neck Surgery
31-20 Rehab Center,
Los Angeles, CA 90095-1794
Phone: +1 (323) 703-9549

Popular version of paper 1pSC26 “Acoustics and Perception of Charisma in Bilingual English-Spanish 2016 United States Presidential Election Candidates”
Presented at the 171st Meeting on Monday May 23, 1:00 pm – 5:00 pm, Salon F, Salt Lake Marriott Downtown at City Creek Hotel, Salt Lake City, Utah,

Charisma is the set of leadership characteristics, such as vision, emotions, and dominance used by leaders to share beliefs, persuade listeners and achieve goals. Politicians use voice to convey charisma and appeal to voters to gain social positions of power. “Charismatic voice” refers to the ensemble of vocal acoustic patterns used by speakers to convey personality traits and arouse specific emotional states in listeners. The ability to manipulate charismatic voice results from speakers’ universal and learned strategies to use specific vocal parameters (such as vocal pitch, loudness, phonation types, pauses, pitch contours, etc.) to convey their biological features and their social image (see Ohala, 1994; Signorello, 2014a, 2014b; Puts et al., 2006). Listeners’ perception of the physical, psychological and social characteristics of the leader is influenced by universal ways to emotionally respond to vocalizations (see Ohala, 1994; Signorello, 2014a, 2014b) combined with specific, culturally-mediated, habits to manifest emotional response in public (Matsumoto, 1990; Signorello, 2014a).

Politicians manipulate vocal acoustic patterns (adapting them to the culture, language, social status, educational background and the gender of the voters) to convey specific types of leadership fulfilling everyone’s expectation of what charisma is. But what happen to leaders’ voice when they use different languages to address voters? This study investigates speeches of bilingual politicians to find out the vocal acoustic differences of leaders speaking in different languages. It also investigates how the acoustical differences in different languages can influence listeners’ perception of type of leadership and the emotional state aroused by leaders’ voices.

We selected vocal samples from two bilingual America-English/American-Spanish politicians that participated to the 2016 United States presidential primaries: Jeb Bush and Marco Rubio. We chose words with similar vocal characteristics in terms of average vocal pitch, vocal pitch range, and loudness range. We asked listeners to rate the type of charismatic leadership perceived and to assess the emotional states aroused by those voices. We finally asked participants how the different vocal patterns would affect their voting preference.

Preliminary statistical analyses show that English words like “terrorism” (voice sample 1) and “security” (voice sample 2), characterized by mid vocal pitch frequencies, wide vocal pitch ranges, and wide loudness ranges, convey an intimidating, arrogant, selfish, aggressive, witty, overbearing, lazy, dishonest, and dull type of charismatic leadership. Listeners from different language and cultural backgrounds also reported these vocal stimuli triggered emotional states like contempt, annoyance, discomfort, irritation, anxiety, anger, boredom, disappointment, and disgust. The listeners who were interviewed considered themselves politically liberal and they responded that they would probably vote for a politician with the vocal characteristics listed above.

Speaker Jeb Bush. Mid vocal pitch frequencies (126 Hz), wide vocal pitch ranges (97 Hz), and wide loudness ranges (35 dB)

Speaker Marco Rubio. Mid vocal pitch frequencies 178 Hz), wide vocal pitch ranges (127 Hz), and wide loudness ranges (30 dB)

Results also show that Spanish words like “terrorismo” (voice sample 3) and “ilegal” (voice sample 4) characterized by an average of mid-low vocal pitch frequencies, mid vocal pitch ranges, and narrow loudness ranges convey a personable, relatable, kind, caring, humble, enthusiastic, witty, stubborn, extroverted, understanding, but also weak and insecure type of charismatic. Listeners from different language and cultural backgrounds also reported these vocal stimuli triggered emotional states like happiness, amusement, relief, and enjoyment. The listeners who were interviewed considered themselves politically liberal and they responded that they would probably vote for a politician with the vocal characteristics listed above.  

Speaker Jeb Bush. Mid-low vocal pitch frequencies (95 Hz), mid vocal pitch ranges (40 Hz), and narrow loudness ranges (17 dB) 

Speaker Marco Rubio. Mid vocal pitch frequencies 146 Hz), wide vocal pitch ranges (75 Hz), and wide loudness ranges (25 dB)

Voice is a very dynamic non-verbal behavior used by politicians to persuade the audience and manipulate voting preference. The results of this study show how acoustic differences in voice convey different types of leadership and arouse differently the emotional states of the listeners. The voice samples studied show how speakers Jeb Bush and Marco Rubio adapt their vocal delivery to audiences of different backgrounds. The two politicians voluntary manipulate their voice parameters while speaking in order to appear as they were endowed of different leadership qualities. The vocal pattern used in English conveys the threatening and dark side of their charisma, inducing the arousal of negative emotions, which triggers a positive voting preference in listeners. The vocal pattern used in English conveys the charming and caring side of their charisma, inducing the arousal of positive emotions, which triggers a negative voting preference in listeners.

The manipulation of voice arouses emotional states that will induce voters to consider a certain type of leadership as more appealing. Experiencing emotions help voters to assess the effectiveness of a political leader. If the emotional arousing matches with voters’ expectation of how a charismatic leader should make them feel then voters would help the charismatic speaker to became their leader.

References
Signorello, R. (2014a). Rosario Signorello (2014). La Voix Charismatique : Aspects Psychologiques et Caractéristiques Acoustiques. PhD Thesis. Université de Grenoble, Grenoble, France and Università degli Studi Roma Tre, Rome, Italy.

Signorello, R. (2014b). The biological function of fundamental frequency in leaders’ charismatic voices. The Journal of the Acoustical Society of America 136 (4), 2295-2295.

Ohala, J. (1984). An ethological perspective on common cross-language utilization of F0 of voice. Phonetica, 41(1):1–16.

Puts, D. A., Hodges, C. R., Cárdenas, R. A. et Gaulin, S. J. C. (2007). Men’s voices as dominance signals : vocal fundamental and formant frequencies influence dominance attributions among men. Evolution and Human Behavior, 28(5):340–344.