Voice Biofeedback via Bone Conduction Headphones: Effects on Acoustic Voice Parameters and Self-Reported Vocal Effort in Individuals With Voice Disorders

Published:November 11, 2022DOI:



      This study explores sidetone amplification (amplified playback of one's own voice) provided via bone conduction in participants with voice disorders. The effects of bone conduction feedback on acoustic voice parameters and vocal effort ratings are examined.


      Speech samples of 47 participants with voice disorders were recorded in three auditory feedback conditions: two with sidetone amplification delivered via bone conduction and one condition with no alteration of the feedback. After each task, the participants rated their vocal effort on a visual analog scale. The voice recordings were evaluated by a speech-language pathologist through the GRBAS scale and processed to calculate the within-participant centered sound pressure level (SPL) values, the mean pitch strength (PS), the time dose (Dt%), and cepstral peak prominence smoothed (CPPS). The effects of the feedback conditions on these acoustic parameters and vocal effort ratings were analyzed.


      The high sidetone amplification condition resulted in a statistically significant decrease in the within-participant centered SPL values and mean pitch strength across all participants. The feedback conditions had no statistically significant effects on the vocal effort ratings, time dose (Dt%), or CPPS.


      This study provides an evidence that bone conduction sidetone amplification contributes to a consistent adaptation in the within-participant centered SPL values (ΔSPL) in patients with vocal hyperfunction, glottal insufficiency, and organic/neurological laryngeal pathologies compared to conditions with no feedback.

      Key Words

      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Journal of Voice
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


      1. OECD. Oecd labour force statistics. 2014. 10.1787/oecdlfs.2014.en. Accessed June 1, 2022, from http://content/book/oecd_lfs-2014-en.

        • Roy N
        • Merrill RM
        • Gray SD
        • et al.
        Voice disorders in the general population: prevalence, risk factors, and occupational impact.
        Laryngoscope. 2005; 115: 1988-1995
        • Hillman RE
        • Stepp CE
        • Van Stan JH
        • et al.
        An updated theoretical framework for vocal hyperfunction.
        Am J Speech Lang Pathol. 2020; 29: 2254-2260
        • Ghassemi M
        • Syed Z
        • Mehta D
        • et al.
        Uncovering voice misuse using symbolic mismatch.
        in: Doshi-Velez F. Proceedings of the 1st Machine Learning for Healthcare Conference, volume 56 of Proceedings of Machine Learning Research. Children's Hospital LA, Los Angeles, CA, USA2016: 239-252 (pagesPMLR)
        • Oates J
        • Winkworth A
        Current knowledge, controversies and future directions in hyperfunctional voice disorders.
        Int J Speech Lang Pathol. 2008; 10: 267-277
        • Maryn Y
        • De Bodt M
        • Van Cauwenberge P
        Effects of biofeedback in phonatory disorders and phonatory performance: a systematic literature review.
        Appl Psychophysiol Biofeedback. 2006; 31: 65-83
        • Ziegler A
        • Dastolfo C
        • Hersan R
        • et al.
        Perceptions of voice therapy from patients diagnosed with primary muscle tension dysphonia and benign mid- membranous vocal fold lesions.
        J Voice. 2014; 28: 742-752
        • Van Stan JH
        • Gustafsson J
        • Schalling E
        • et al.
        Direct comparison of three commercially available devices for voice ambulatory monitoring and biofeedback.
        Perspectives Voice Voice Disord. 2014; 24: 80-86
        • Schalling E
        • Gustafsson J
        • Ternstrom S
        • et al.
        Effects of tactile biofeedback by a portable voice accumulator on voice sound level in speakers with Parkinson's disease.
        J Voice. 2013; 27: 729-737
        • Morsomme D
        • Remacle A
        Can ambulatory biofeedback help a transgender woman speak at a Peters, R. W., The effect of filtering of sidetone upon speaker intelligibility.
        Speech Hear Dis. 2021; 20 (1955): 371-375
        • Van Stan JH
        • Ortiz AJ
        • Sternad D
        • et al.
        Ambulatory voice biofeedback: acquisition and retention of modified daily voice use in patients with phonotraumatic vocal hyperfunction.
        Am J Speech Lang Pathol. 2021; 31: 409-418
        • Van Stan JH
        • Mehta DD
        • Petit RJ
        • et al.
        Integration of motor learning principles into real-time ambulatory voice biofeedback and example implementation via a clinical case study with vocal fold nodules.
        Am J Speech Lang Pathol. 2017; 26 (a): 1-10
        • van Mersbergen M
        • Beckham BH
        • Hunter EJ
        Do we need a measure of vocal effort? Clinician's report of vocal effort in voice patients.
        Perspect ASHA Special Interest Groups. 2020; 6: 69-79 PERSP-20-00258
        • Hunter EJ
        • Cantor-Cutiva LC
        • van Leer E
        • et al.
        Toward a consensus description of vocal effort, vocal load, vocal loading, and vocal fatigue.
        J Speech Lang Hear Res. 2020; 63: 509-532
        • Hanschmann H
        • Lohmann A
        • Berger R
        Comparison of subjective assessment of voice disorders and objective voice measurement.
        Folia Phoniatr Logop. 2011; 63: 83-87
        • Colton RH
        • Casper JK
        • Leonard RJ
        Understanding Voice Problems: A Physiological Perspective for Diagnosis and Treatment.
        4th. Lippincott Williams & Wilkins, Baltimore, MD2006
        • Jiang JJ
        • Titze IR
        Measurement of vocal fold intraglottal pressure and impact stress.
        J Voice. 1994; 8: 132-144
        • Marks KL
        • Verdi A
        • Toles LE
        • et al.
        Psychometric analysis of an ecological vocal effort scale in individuals with and without vocal hyperfunction during activities of daily living.
        Am J Speech Lang Pathol. 2021; 30: 2589-2604
        • Van Stan JH
        • Maffei M
        • Masson MLV
        • et al.
        Self-ratings of vocal status in daily life: reliability and validity for patients with vocal hyperfunction and a normative group.
        Am J Speech Lang Pathol. 2017; 26 (b): 1167-1177
        • Arciuli J
        • Simpson BS
        • Vogel AP
        • et al.
        Acoustic changes in the production of lexical stress during Lombard speech.
        Lang Speech. 2013; 57: 149-162
        • Garnier M
        • Henrich N
        • Dubois D
        Influence of sound immersion and communicative interaction on the Lombard effects.
        J Speech Lang Hear Res. 2010; 53: 588-608
        • Stathopoulos ET
        • Huber JE
        • Richardson K
        • et al.
        Increased vocal intensity due to the Lombard effect in speakers with Parkinson's disease: Simultaneous laryngeal and respiratory strategies.
        J Commun Disord. 2014; 48: 1-17
        • Rubin AD
        • Codino J
        • Costeloe A
        • et al.
        The effect of unilateral hearing protection on vocal intensity with varying degrees of background noise.
        J Voice. 2021; 35: 886-891
        • Burnett TA
        • Freedland MB
        • Larson CR
        • et al.
        Voice F0 responses to manipulations in pitch feedback.
        J Acoust Soc Am. 1998; 103: 3153-3161
        • Jones JA
        • Munhall KG
        Perceptual calibration of F0 production: evidence from feedback perturbation.
        J Acoust Soc Am. 2000; 108: 1246-1251
        • Jones JA
        • Munhall KG
        Remapping auditory-motor representations in voice production.
        Curr Biol. 2005; 15: 1768-1772
        • Larson CR
        • Burnett TA
        • Kiran S
        • et al.
        Effects of pitch- shift velocity on voice F0 responses.
        J Acoust Soc Am. 2000; 107: 559-564
        • Chen SH
        • Liu H
        • Xu Y
        • Larson CR
        Voice F0 responses to pitch-shifted voice feedback during English speech.
        J Acoust Soc Am. 2007; 121: 1157-1163
        • Behroozmand R
        • Karvelis L
        • Liu H
        • et al.
        Vocalization- induced enhancement of the auditory cortex responsiveness during voice F0 feedback perturbation.
        Clin Neurophysiol. 2009; 120: 1303-1312
        • Liu H
        • Meshman M
        • Behroozmand R
        • et al.
        Differential effects of perturbation direction and magnitude on the neural processing of voice pitch feedback.
        Clin Neurophysiol. 2011; 122: 951-957
        • Schenck A
        • Hilger AI
        • Levant S
        • et al.
        The effect of pitch and loudness auditory feedback perturbations on vocal quality during sustained phonation.
        J Voice. 2020.;
        • Ning L-H
        Comparison of involuntary and volitional responses to pitch-shifted auditory feedback: evidence for tone Speakers’ flexibility to switch between opposing and following responses.
        J Speech Lang Hear Res. 2022; : 1-27
        • Abur D
        • Subaciute A
        • Daliri A
        • et al.
        Feedback and feedforward auditory–motor processes for voice and articulation in Parkinson's disease.
        J Speech Lang Hear Res. 2021; 64 (a): 4682-4694
        • Abur D
        • Lester-Smith RA
        • Daliri A
        • et al.
        Sensorimotor adaptation of voice fundamental frequency in Parkinson's disease.
        PLoS One. 2018; 13e0191839
        • Mollaei F
        • Shiller DM
        • Baum SR
        • et al.
        Sensorimotor control of vocal pitch and formant frequencies in Parkinson's disease.
        Brain Res. 2016; 1646: 269-277
        • Mollaei F
        • Shiller DM
        • Baum SR
        • et al.
        The relationship between speech perceptual discrimination and speech production in Parkinson's disease.
        J Speech Lang Hear Res. 2019; 62: 4256-4268
        • Liu H
        • Wang EQ
        • Metman LV
        • et al.
        Vocal responses to perturbations in voice auditory feedback in individuals with Parkinson's disease.
        PLoS One. 2012; 7: e33629
        • Kiran S
        • Larson CR
        Effect of duration of pitchs hifted feedback on vocal responses in patients with Parkinson's disease.
        J Speech Lang Hear Res. 2001; 44: 975-987
        • Hilger AI
        Impaired Sensorimotor Integration for Prosodic Production in Ataxic Dysarthria.
        Northwestern University, 2020 (Available at)
        • Houde JF
        • Gill JS
        • Agnew Z
        • et al.
        Abnormally increased vocal responses to pitch feedback perturbations in patients with cerebellar degeneration.
        J Acoust Soc Am. 2019; 145: EL372-EL378
        • Abur D
        • Subaciute A
        • Kapsner-Smith M
        • et al.
        Impaired auditory discrimination and auditory–motor integration in hyperfunctional voice disorders.
        Sci Rep. 2021; 11: 13123
        • Stepp CE
        • Lester-Smith RA
        • Abur D
        • et al.
        Evidence for auditory-motor impairment in individuals with hyperfunctional voice disorders.
        J Speech Lang Hear Res. 2017; 60: 1545-1550
        • Naunheim ML
        • Yung KC
        • Schneider SL
        • et al.
        Vocal motor control and central auditory impairments in unilateral vocal fold paralysis.
        Laryngoscope. 2019; 129: 2112-2117
        • Thomas A
        • Mirza N
        • Eliades SJ
        Auditory feedback control of vocal pitch in spasmodic dysphonia.
        Laryngoscope. 2021; 131: 2070-2075
        • Houde JF
        • Jordan MI
        Sensorimotor adaptation of speech: I. Compensation and adaptation.
        J. Speech Lang. Hear. Res. 2002; 45: 295-310
        • Purcell DW
        • Munhall KG
        Compensation following real-time manipulation of formants in isolated vowels.
        J Acoust Soc Am. 2006; 119 (b): 2288-2297
        • Villacorta VM
        • Perkell JS
        • Guenther FH
        Sensorimotor adaptation to feedback perturbations of vowel acoustics and its relation to perception.
        J Acoust Soc Am. 2007; 122: 2306-2319
        • Munhall KG
        • Macdonald EN
        • Byrne SK
        • et al.
        Talkers alter vowel production in response to real-time formant perturbation even when instructed not to compensate.
        J Acoust Soc Am. 2009; 125: 384-390
        • MacDonald EN
        • Goldberg R
        • Munhall KG
        Compensations in response to real-time formant perturbations of different magnitudes.
        J Acoust Soc Am. 2010; 127: 1059-1068
        • MacDonald EN
        • Purcell DW
        • Munhall KG
        Probing the independence of formant control using altered auditory feedback.
        J Acoust Soc Am. 2011; 129: 955-965
        • MacDonald EN
        • Johnson EK
        • Forsythe J
        • et al.
        Children's development of self-regulation in speech production.
        Curr Biol. 2012; 22: 113-117
        • Mitsuya T
        • Macdonald EN
        • Purcell DW
        • et al.
        A cross- language study of compensation in response to real-time formant perturbation.
        J Acoust Soc Am. 2011; 130: 2978-2986
        • Lametti DR
        • Nasir SM
        • Ostry DJ
        Sensory preference in speech production revealed by simultaneous alteration of auditory and somatosensory feedback.
        J Neurosci. 2012; 32: 9351-9358
        • Ziethe A
        • Petermann S
        • Hoppe U
        • et al.
        Control of fundamental frequency in dysphonic patients during phonation and speech.
        J Voice. 2019; 33: 851-859
        • Castro C
        • Prado P
        • Espinoza VM
        • et al.
        Lombard effect in individuals with nonphonotraumatic vocal hyperfunction: impact on acoustic, aerodynamic, and vocal fold vibratory parameters.
        J Speech Lang Hear Res. 2022; 65: 2881-2895
        • Weerathunge HR
        • Tomassi NE
        • Stepp CE
        What can altered auditory feedback paradigms tell us about vocal motor control in individuals with voice disorders?.
        Perspect ASHA Spec Interest Groups. 2022; Mar: 1-18
        • Senthinathan A
        • Adams S
        • Page AD
        • et al.
        Speech intensity response to altered intensity feedback in individuals with Parkinson's disease.
        J Speech Lang Hear Res. 2021; 64: 2261-2275
        • Tomassi NE
        • Castro ME
        • Sund LT
        • et al.
        Effects of sidetone amplification on vocal function during telecommunication.
        J Voice. 2021; Advance online publication
        • Laukkanen AM
        • Mickelson NP
        • Laitala M
        • et al.
        Effects of HearFones on speaking and singing voice quality.
        J Voice. 2004; 18: 475-487
        • Fletcher H
        • Raff GM
        • Parmley F
        Study of the effects of different sidetones in the telephone set.
        Western Electrical Company, Report, (19412). 1918; Case no. 120622
        • Lane H
        • Tranel B
        The Lombard sign and the role of hearing in speech.
        J Speech Hear Res. 1971; 14: 677-709
        • Merson RM
        Auditory sidetone and the management of stuttering: from Wollensak to SpeechEasy.
        in: 6th International Stuttering Awareness Day Online Conference (ISAD6). 2003 (Link:)
        • Lindholm O
        Preferred EQ-setting for Highest Comfort When Listening to One’s Own Voice Through Headphones While Speaking.
        Luleå University of Technologys, Luleå, Sweden2014 (Bachelor’s thesis)
        • Lewis AL
        The effect of realtime auditory feedback on selected aspects of vocal performance (Doctoral dissertation, Indiana University).
        Indiana University, Bloomington, Indiana1987 (Available at:)
        • Cafaro A
        • Arneson C
        Audio technology: a tool for teachers and singers.
        J Singing. 2020; 76: 311-315
        • Bauer JJ
        • Mittal J
        • Larson CR
        • et al.
        Vocal responses to unanticipated perturbations in voice loudness feedback: an automatic mechanism for stabilizing voice amplitude.
        J Acoust Soc Am. 2006; 119: 233-2371
        • Heinks-Maldonado TH
        • Houde JF
        Compensatory responses to brief perturbations of speech amplitude.
        Acoust Res Lett Online. 2005; 6: 131-137
        • Garber SR
        • Siegel GM
        • Pick Jr., HL
        The influence of selected masking noises on Lombard and sidetone amplification effects.
        J Speech Hear Res. 1976; 19: 523-535
        • Pelegrín-García D
        • Brunskog J
        Speakers’ comfort and voice level variation in classrooms: laboratory research.
        J Acoust Soc America. 2012; 132: 249-260
        • Bottalico P
        • Graetzer S
        • Hunter EJ
        Effects of voice style, noise level, and acoustic feedback on objective and subjective voice evaluations.
        J Acoust Soc Am. 2015; 138 (a): EL498-EL503
        • Sierra-Polanco T
        • Cantor-Cutiva LC
        • Hunter EJ
        • et al.
        Changes of voice production in artificial acoustic environments.
        Front Built Environ. 2021; 7: 71
        • Henry P
        • Letowski TR
        Bone conduction: Anatomy, physiology, and communication.
        Army Research Lab Aberdeen Proving Ground Md Human Research And Engineering Directorate. Army Research Laboratory, Aberdeen Proving Ground, Maryland2007
        • Bekesy GV
        Zur Theorie des Hörens bei der Schallaufnahme durch Knochenleoitung.
        Ann Physik. 1932; 8: 111-136
        • Lowy K
        Cancellation of the electrical cochlear response with air- and bone-conduction.
        J Acoust Soc Am. 1942; 14: 156-158
        • Feldmann H
        History of the tuning fork. II: evolution of the classical experiments by Weber.
        Rinne and Schwabach. Laryngo-rhino-otologie. 1997; 76: 318-326
        • Escera C
        • López-Caballero F
        • Gorina-Careta N
        The potential effect of forbrain as an altered auditory feedback device.
        J Speech Lang Hear Res. 2018; 61 (a): 801-810
        • Escera C
        • Gorina-Careta N
        • López-Caballero F
        The potential use of Forbrain® in stuttering: a single-case study.
        Anuario de Psicología. 2018; 48: 51-58
        • Jinju S
        • Changxiang C
        • Min Z
        • et al.
        Speech-auditory feedback training on cognitive dysfunctions in stroke patients.
        Chinese J Behav Med Brain Sci. 2017; : 26
        • McBride M
        • Tran P
        • Letowski T
        • et al.
        The effect of bone conduction microphone locations on speech intelligibility and sound quality.
        Appl Ergon. 2011; 42: 495-502
        • McBride M
        • Hodges M
        • French J
        Speech intelligibility differences of male and female vocal signals transmitted through bone conduction in background noise: Implications for voice communication headset design.
        Int J Ind Ergon. 2008; 38: 1038-1044
        • Lee SH
        • Yu JF
        • Fang TJ
        • et al.
        Vocal fold nodules: a disorder of phonation organs or auditory feedback?.
        Clin Otolaryngol. 2019; 44: 975-982
        • Nanjundeswaran C
        • Li NY
        • Chan KM
        • et al.
        Preliminary data on prevention and treatment of voice problems in student teachers.
        J Voice. 2012; 26 (30): e811-e812
        • Salturk Z
        • Ozdemir E
        • Sari H
        • et al.
        Assessment of resonant voice therapy in the treatment of vocal fold nodules.
        J Voice. 2018;
        • Shrivastav R
        • Eddins DA
        • Anand S
        Pitch strength of normal and dysphonic voices.
        J Acoust Soc Am. 2012; 131: 2261-2269
        • Zwicker E
        • Fastl H
        Psychoacoustics: Facts and Models. 22. Springer Science & Business Media, Berlin, Germany2013
        • Anand S
        • Kopf LM
        • Shrivastav R
        • et al.
        Using pitch height and pitch strength to characterize type 1, 2, and 3 voice signals.
        J Voice. 2021; 35: 181-193
        • Meddis R
        • Hewitt MJ
        Virtual pitch and phase sensitivity of a computer model of the auditory periphery. I: Pitch identification.
        J Acoust Soc Am. 1991; 89: 2866-2882
        • Kopf LM
        • Jackson-Menaldi C
        • Rubin AD
        • et al.
        Pitch strength as an outcome measure for treatment of dysphonia.
        J Voice. 2017; 31: 691-696
        • Titze IR
        • Švec JG
        • Popolo PS
        Vocal dose measures: quantifying accumulated vibration exposure in vocal fold tissues.
        J Speech Lang Hear Res. 2003; 46: 919-932
        • Astolfi A
        • Bottalico P
        • Accornero A
        • et al.
        Relationship between vocal doses and voice disorders on primary school teachers.
        Proc Euronoise. 2012; 9: 55-60
        • Assad JP
        • Gama ACC
        • Santos JN
        • et al.
        The effects of amplification on vocal dose in teachers with dysphonia.
        J Voice. 2019; 33: 73-79
        • Gaskill CS
        • O'Brien SG
        • Tinter SR
        The effect of voice amplification on occupational vocal dose in elementary school teachers.
        J Voice. 2012; 26: e667-e679
        • Morrow SL
        • Connor NP
        Voice amplification as a means of reducing vocal load for elementary music teachers.
        J Voice. 2011; 25: 441-446
        • Rosen CA
        • Lee AS
        • Osborne J
        • et al.
        Development and validation of the voice handicap index-10.
        Laryngoscope. 2004; 114: 1549-1556
        • Hirano M
        Clinical Examination of Voice.
        Springer-Verlag, New York, NY1981
        • Bassi IB
        • Assunção AÁ
        • de Medeiros AM
        • et al.
        Quality of life, self-perceived dysphonia, and diagnosed dysphonia through clinical tests in teachers.
        J Voice. 2011; 25: 192-201
        • Cantor Cutiva LC
        • Burdorf A
        Objective voice parameters in Colombian school workers with healthy voices.
        Revista Ciencias de la Salud. 2015; 13: 331-344
        • Bottalico P
        • Codino J
        • Cantor-Cutiva LC
        • et al.
        Reproducibility of voice parameters: the effect of room acoustics and microphones.
        J Voice. 2020; 34: 320-334
        • Fairbanks G
        The rainbow passage.
        Voice and articulation drillbook. 1960; 2 (127-127)
        • Guenther FH
        • Perkell JS
        A neural model of speech production and its application to studies of the role of auditory feedback in speech.
        in: Maassen B Kent R Peters HFM Van Lieshout P Hulstijn W Speech Motor Control in Normal and Disordered Speech. Oxford University Press, Oxford, United Kingdom2004: 29-49
        • Guenther FH
        Neural Control of Speech.
        MIT Press, 2016
        • Tourville JA
        • Reilly KJ
        • Guenther FH
        Neural mechanisms underlying auditory feedback control of speech.
        Neuroimage. 2008; 39: 1429-1443
        • Behroozmand R
        • Sangtian S
        Neural bases of sensorimotor adaptation in the vocal motor system.
        Exp Brain Res. 2018; 236: 1881-1895
        • Keough D
        • Jones JA
        The sensitivity of auditorymotor representations to subtle changes in auditory feedback while singing.
        J Acoust Soc Am. 2009; 126: 837-846
        • Spencer ML
        Muscle tension dysphonia: a rationale for symptomatic subtypes, expedited treatment, and increased therapy compliance.
        Perspectives On Voice And Voice Disorders. 2015; 25: 5-15
        • Lee S-H
        • Torng P-C
        • Lee G-S
        Contributions of forward-focused voice to audio-vocal feedback measured using nasal accelerometry and power spectral analysis of vocal fundamental frequency.
        J Speech Lang Hear Res. 2022; : 1-16
        • Filter M
        Phonatory Voice Disorders in Children.
        C.C. Thomas, Springfield, CA1982
        • Watts CR
        • Diviney SS
        • Hamilton A
        • et al.
        The effect of stretch-and-flow voice therapy on measures of vocal function and handicap.
        J Voice. 2015; 29: 191-199
        • Thomas LB
        • Stemple JC
        Voice therapy: does science support the art?.
        Communicative Disorders Review. 2007; 1: 49-77
        • Verdolini-Marston K
        • Burke MK
        • Lessac A
        • et al.
        Preliminary study of two methods of treatment for laryngeal nodules.
        J Voice. 1995; 9: 74-85
        • Whittico TH
        • Ortiz AJ
        • Marks KL
        • et al.
        Ambulatory monitoring of Lombard-related vocal characteristics in vocally healthy female speakers.
        J Acoust Soc Am. 2020; 147: EL552-EL558
        • Bottalico P
        • Graetzer S
        • Hunter EJ
        Effects of speech style, room acoustics, and vocal fatigue on vocal effort.
        J Acoust Soc Am. 2016; 139: 2870
        • Bottalico P
        • Graetzer S
        • Hunter E
        Vocal effort and the effect of room acoustics in noisy environments.
        in: Burroughs C Proceedings of the 44th International Congress and Exposition on Noise Control Engineering. Institute of Noise Control Engineering, San Francisco, California2015: 4688-4698
        • Lindstrom F
        • Waye KP
        • Södersten M
        • et al.
        Observations of the relationship between noise exposure and preschool teacher voice usage in day-care center environments.
        J Voice. 2011; 25: 166-172
        • Jónsdottir V
        • Rantala L
        • Laukkanen AM
        • et al.
        Effects of sound amplification on teachers’ speech while teaching.
        Logoped Phoniatr Vocol. 2001; 26: 118-123
        • Jónsdottir V
        • Laukkanen AM
        • Vilkman E
        Changes in teachers’ speech during a working day with and without electric sound amplification.
        Folia Phoniatr Logop. 2002; 54: 282-287
        • Jónsdottir V
        • Laukkanen AM
        • Siikki I
        Changes in teachers’ voice quality during a working day with and without electric sound amplification.
        Folia Phoniatr Logop. 2003; 55: 267-280
        • McCormick CA
        • Roy N
        The ChatterVox™ portable voice amplifier: a means to vibration dose reduction?.
        J Voice. 2002; 16: 502-508
        • Roy N
        • Weinrich B
        • Gray SD
        • et al.
        Three treatments for teachers with voice disorders: a randomized clinical trial.
        J Speech Lang Hear Res. 2003; 46: 670-688
        • Hétu R
        • Truchon-Gagnon C
        • Bilodeau SA
        Problems of noise in school settings: a review of literature and the results of an exploratory study.
        J Speech Lang Pathol Audiol. 1990; 14: 31-39
        • Kob M
        • Behler G
        • Kamprolf A
        • et al.
        Experimental investigations of the influence of room acoustics on the teacher's voice.
        Acoustical Sci Technol. 2008; 29: 86-94
        • Bottalico P
        • Astolfi A
        • Hunter EJ
        Teachers' voicing and silence periods during continuous speech in classrooms with different reverberation times.
        J Acoust Soc Am. 2017; 141 (a): EL26-EL31
        • Redman Y
        • Vercelli C
        • Cantor-Cutiva LC
        • et al.
        Work-related communicative profile of voice teachers: effects of classroom noise on voice and hearing abilities.
        J Voice. 2020; 36: 291.e17-291.e31
        • Bottalico P
        Speech adjustments for room acoustics and their effects on vocal effort.
        J Voice. 2017; 31: 392-e401
        • Mehta DD
        • Van Stan JH
        • Hillman RE.
        Relationships between vocal function measures derived from an acoustic microphone and a subglottal neck-surface accelerometer.
        IEEE/ACM Trans Audio Speech Lang Process. 2016; 24: 659-668
        • Nudelman CJ
        • Ortiz AJ
        • Fox AB
        • et al.
        Daily phonotrauma index: an objective indicator of large differences in self-reported vocal status in the daily life of females with phonotraumatic vocal hyperfunction.
        Am J Speech Lang Pathol. 2022; 31: 1412-1423
        • Bottalico Pasquale
        • Ipsaro Passione Ivano
        • Graetzer Simone
        • et al.
        Evaluation of the starting point of the Lombard effect.
        Acta Acustica United With Acustica. 2017; 103 (b): 169-172
        • Coleman RF
        Comparison of microphone and neckmounted accelerometer monitoring of the performing voice.
        J Voice. 1988; 2: 200-205
        • Svec JG
        • Titze IR
        • Popolo PS
        Estimation of sound pressure levels of voiced speech from skin vibration of the neck.
        J Acoust Soc Am. 2005; 117: 1386-1394
        • Verdolini K
        • Rosen CA
        • Branski RC
        Classification Manual for Voice Disorders-I.
        Psychology Press, London, England, United Kingdom2014
        • Won SY
        • Berger J
        Estimating Transfer Function From Air to Bone Conduction Using Singing Voice.
        International Computer Music Association, 2005 (Available at)
        • Bovo R
        • Trevisi P
        • Emanuelli E
        • et al.
        Voice amplification for primary school teachers with voice disorders: a randomized clinical trial.
        Int J Occup Med Environ Health. 2013; 26: 363-372
        • Schwartz MS
        • Collura TF
        • Kamiya J
        • et al.
        The history and definitions of biofeedback and applied psychophysiology.
        in: Andrasik F, Biofeedback: A Practitioner's Guide. 4th ed. Guilford, NY2006: 3-23
        • Chen X
        • Zhu X
        • Wang EQ
        • et al.
        Sensorimotor control of vocal pitch production in Parkinson's disease.
        Brain Res. 2013; 1527: 99-107
        • Chen SH
        • Hsiao TY
        • Hsiao LC
        • et al.
        Outcome of resonant voice therapy for female teachers with voice disorders: perceptual, physiological, acoustic, aerodynamic, and functional measurements.
        J Voice. 2007; 21 (29): 415-425