Measurements of the effect of interventions on heathly voices: a scope review

Moura, Luiza Maria das Graças Mayhampsan Oliveira de; Silva, Priscila Oliveira Costa; Santana, Émile Rocha; Batista, Denis de Jesus; da Trindade Duarte, João Marcos; Ribeiro, Vanessa Veis; Almeida, Anna Alice Figueiredo de; Lopes, Leonardo Wanderley

doi:10.1590/2317-6431-2022-2769pt

person Luiza Maria das Graças Mayhampsan Oliveira de Moura

conception · execution · tabulation · data analysis and writing of the manuscript

schoolDepartamento de Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0003-4068-7989

person Priscila Oliveira Costa Silva

conception · tabulation and supervision of the study

schoolDepartamento de Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma Associado de Pós-Graduação em Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0002-2410-1442

person Émile Rocha Santana

data collection and extraction

schoolPrograma de Pós-Graduação em Modelos de Decisão e Saúde, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0002-0588-7902

person Denis de Jesus Batista

data collection and extraction

schoolPrograma Associado de Pós-Graduação em Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0001-6716-0664

person João Marcos da Trindade Duarte

data collection and extraction

schoolPrograma de Pós-Graduação em Linguística, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0003-0073-818X

person Vanessa Veis Ribeiro

data collection and extraction

schoolPrograma Associado de Pós-Graduação em Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma de Pós-Graduação em Ciência Médicas, Universidade de Brasília - UnB - Brasília (DF), Brasil.

0000-0002-3089-6085

person Anna Alice Figueiredo de Almeida

writing and correction of the manuscript

schoolDepartamento de Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma Associado de Pós-Graduação em Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma de Pós-Graduação em Modelos de Decisão e Saúde, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0002-9119-5629

person Leonardo Wanderley Lopes

preparation of the study · writing and revision of the manuscript

schoolDepartamento de Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma Associado de Pós-Graduação em Fonoaudiologia, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma de Pós-Graduação em Modelos de Decisão e Saúde, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.schoolPrograma de Pós-Graduação em Linguística, Universidade Federal da Paraíba - UFPB - João Pessoa (PB), Brasil.

0000-0001-9041-7114

Conflict of interests: No.

Corresponding author: Leonardo Wanderley Lopes. E-mail:
lwlopes@hotmail.com

Databases	Strategy	Number of mapped studies
PubMed/ MEDLINE	(("healthy volunteers"[MeSH] OR "healthy volunteers" OR "Normal Speakers" OR "normal healthy participants" OR "healthy adult" OR "healthy subject" OR "healthy subjects" OR "healthy volunteer" OR "normal humans" OR "normal subject" OR "normal subjects" OR "normal volunteer" OR "normal volunteers") AND ("voice training"[MeSH] "voice training" OR "Speech Therapy"[MeSH] OR "Speech Therapy" OR "vocal exercise" OR "vocal hygiene" OR "voice therapy" OR "vocal therapy" OR "Voice Rehabilitation" OR "vocal rehabilitation" OR "vocal intervention" OR "vocal interventions" OR "Voice Treatment" OR "Voice Treatments" OR ("Physical Functional Performance"[Mesh] AND Voice[Mesh]) OR ("Warm-Up Exercise"[Mesh] AND Voice[Mesh]) OR (Intervention AND Voice[Mesh]) OR (Exercise AND Voice[Mesh])) AND ("self assessment"[MeSH] OR "self assessment" OR "speech acoustics"[MeSH] OR "speech acoustics" OR "laryngoscope"[MeSH] OR "laryngoscope" OR "stroboscopy"[MeSH] OR "stroboscopy" OR "voice quality"[MeSH] OR "voice quality" OR "acoustic analysis" OR "glottography" OR "voice parameter" OR "rating scales" OR "objective voice measurements" OR "auditory-perceptual evaluation of voice" OR "voice assessment" OR "aerodynamics" OR "aerodynamic" OR "Patient Reported Outcome Measures"[MeSH] OR "Patient Reported Outcome Measures" OR "patient-reported outcome" OR "outcome assessment"))	274
LILACS (VHL)	((healthy volunteers) OR (healthy volunteers) OR (Normal Speakers) OR (normal healthy participants) OR (healthy adult) OR (healthy subject) OR (healthy subjects) OR (healthy volunteer) OR (normal humans) OR (normal subject) OR (normal subjects) OR (normal volunteer) OR (normal volunteers)) AND ((voice training) OR (voice training) OR (Speech Therapy) OR (Speech Therapy) OR (vocal exercise) OR (vocal hygiene) OR (voice therapy) OR (vocal therapy) OR (Voice Rehabilitation) OR (vocal rehabilitation) OR (vocal intervention) OR (vocal interventions) OR (Voice Treatment) OR (Voice Treatments) OR (Physical Functional Performance) OR (Warm-Up Exercise) OR (Intervention) OR (Exercise) AND (Voice)) AND ((self assessment) OR (self assessment) OR (speech acoustics) OR (speech acoustics) OR (laryngoscope) OR (laryngoscope) OR (stroboscopy) OR (stroboscopy) OR (voice quality) OR (voice quality) OR (acoustic analysis) OR (glottography) OR (voice parameter) OR (rating scales) OR (objective voice measurements) OR (auditory-perceptual evaluation of voice) OR (voice assessment) OR (aerodynamics) OR (aerodynamic) OR (Patient Reported Outcome Measures) OR (Patient Reported Outcome Measures) OR (patient-reported outcome) OR (outcome assessment))	69
Scopus (Elsevier)	(TITLE-ABS-KEY ("healthy volunteers" OR "Normal Speakers" OR "normal healthy participants" OR "healthy adult" OR "healthy subject" OR "healthy subjects" OR "healthy volunteer" OR "normal humans" OR "normal subject" OR "normal subjects" OR "normal volunteer" OR "normal volunteers") AND TITLE-ABS-KEY ("voice training" OR "Speech Therapy" OR "vocal exercise" OR "vocal hygiene" OR "voice therapy" OR "vocal therapy" OR "Voice Rehabilitation" OR "vocal rehabilitation" OR "vocal intervention" OR "vocal interventions" OR "Voice Treatment" OR "Voice Treatments") OR TITLE-ABS-KEY ("Physical Functional Performance" OR "Warm-Up Exercise" OR intervention OR exercise AND voice) AND TITLE-ABS-KEY ("self assessment" OR "speech acoustics" OR "laryngoscope" OR "stroboscopy" OR "voice quality" OR "acoustic analysis" OR "glottography" OR "voice parameter" OR "rating scales" OR "objective voice measurements" OR "auditory-perceptual evaluation of voice" OR "voice assessment" OR "aerodynamics" OR "aerodynamic" OR "Patient Reported Outcome Measures" OR "patient-reported outcome" OR "outcome assessment"))	235
Web of Science (Clarivate)	(TS=("healthy volunteers" OR "healthy volunteers" OR "Normal Speakers" OR "normal healthy participants" OR "healthy adult" OR "healthy subject" OR "healthy subjects" OR "healthy volunteer" OR "normal humans" OR "normal subject" OR "normal subjects" OR "normal volunteer" OR "normal volunteers") AND TS=("voice training" OR "voice training" OR "Speech Therapy" OR "Speech Therapy" OR "vocal exercise" OR "vocal hygiene" OR "voice therapy" OR "vocal therapy" OR "Voice Rehabilitation" OR "vocal rehabilitation" OR "vocal intervention" OR "vocal interventions" OR "Voice Treatment" OR "Voice Treatments" OR "Physical Functional Performance" AND “Voice” OR "Warm-Up Exercise" AND “Voice” OR “Intervention” AND “Voice” OR “Exercise” AND “Voice”) AND TS=("self assessment" OR "self assessment" OR "speech acoustics" OR "speech acoustics" OR "laryngoscope" OR "laryngoscope" OR "stroboscopy” OR "stroboscopy" OR "voice quality" OR "voice quality" OR "acoustic analysis" OR "glossography" OR "voice parameter" OR "rating scales" OR "objective voice measurements" OR "auditory-perceptual evaluation of voice" OR "voice assessment" OR "aerodynamics" OR "aerodynamic" OR "Patient Reported Outcome Measures" OR "Patient Reported Outcome Measures" OR "patient-reported outcome" OR "outcome assessment"))	26
EMBASE	('healthy volunteers'/exp OR 'healthy volunteers' OR 'normal speakers' OR 'normal healthy participants' OR 'healthy adult'/exp OR 'healthy adult' OR 'healthy subject'/exp OR 'healthy subject' OR 'healthy subjects'/exp OR 'healthy subjects' OR 'healthy volunteer'/exp OR 'healthy volunteer' OR 'normal humans'/exp OR 'normal humans' OR 'normal subject'/exp OR 'normal subject' OR 'normal subjects'/exp OR 'normal subjects' OR 'normal volunteer'/exp OR 'normal volunteer' OR 'normal volunteers'/exp OR 'normal volunteers') AND (((('voice training'/exp OR 'voice training' OR 'speech therapy'/exp OR 'speech therapy' OR 'vocal exercise' OR 'vocal hygiene'/exp OR 'vocal hygiene' OR 'voice therapy'/exp OR 'voice therapy' OR 'vocal therapy' OR 'voice rehabilitation'/exp OR 'voice rehabilitation' OR 'vocal rehabilitation'/exp OR 'vocal rehabilitation' OR 'vocal intervention' OR 'vocal interventions' OR 'voice treatment' OR 'voice treatments' OR 'physical functional performance'/exp OR 'physical functional performance') AND ('voice'/exp OR 'voice') OR 'warm-up exercise'/exp OR 'warm-up exercise') AND ('voice'/exp OR 'voice') OR 'intervention'/exp OR 'intervention') AND ('voice'/exp OR 'voice') OR 'exercise'/exp OR 'exercise') AND ('voice'/exp OR 'voice') AND ('self assessment'/exp OR 'self assessment' OR 'speech acoustics'/exp OR 'speech acoustics' OR 'laryngoscope'/exp OR 'laryngoscope' OR 'stroboscopy'/exp OR 'stroboscopy' OR 'voice quality'/exp OR 'voice quality' OR 'acoustic analysis'/exp OR 'acoustic analysis' OR 'glottography'/exp OR 'glottography' OR 'voice parameter'/exp OR 'voice parameter' OR 'rating scales' OR 'objective voice measurements' OR 'auditory-perceptual evaluation of voice' OR 'voice assessment' OR 'aerodynamics'/exp OR 'aerodynamics' OR 'aerodynamic'/exp OR 'aerodynamic' OR 'patient reported outcome measures'/exp OR 'patient reported outcome measures' OR 'patient-reported outcome'/exp OR 'patient-reported outcome' OR 'outcome assessment'/exp OR 'outcome assessment')	304
Cochrane	“healthy volunteers” OR “Normal Speakers” OR “normal healthy participants” OR “healthy adult” OR “healthy subject” OR “healthy subjects” OR “healthy volunteer” OR “normal humans” OR “normal subject” OR “normal subjects” OR “normal volunteer” OR “normal volunteers” in All Text AND "voice training" OR “Speech Therapy" OR “vocal exercise" OR "vocal hygiene" OR "voice therapy" OR "vocal therapy" OR "Voice Rehabilitation" OR "vocal rehabilitation" OR "vocal intervention" OR "vocal interventions" OR "Voice Treatment" OR "Voice Treatments" OR "Physical Functional Performance" AND “Voice” OR "Warm-Up Exercise" AND “Voice” OR “Intervention” AND “Voice” OR “Exercise” AND “Voice” in Title Abstract Keyword AND "self assessment" OR "speech acoustics" OR “laryngoscope” OR “stroboscopy” OR "voice quality" OR "acoustic analysis" OR "glottography" OR "voice parameter" OR "rating scales" OR "objective voice measurements" OR "auditory-perceptual evaluation of voice" OR "voice assessment" OR "aerodynamics" OR "aerodynamic" OR “Patient Reported Outcome Measures” OR “patient-reported outcome” OR “outcome assessment” in Title Abstract Keyword - (Word variations have been searched)	71

VARIABLES	STUDIES INVESTIGATED
TYPE OF RESEARCH
Quasi-experimental	(¹⁴, ³³, ³⁹, ⁴², ⁴⁹, ⁵³, ⁵⁸, ⁵⁹, ⁶¹, ⁶⁷, ⁷¹, ⁸¹, ⁸⁶, ⁹⁷, ⁹⁹, ¹⁰², ¹⁰⁵, ¹⁰⁶, ¹⁰⁹, ¹¹⁰)
Before-and-after	(¹⁵, ¹⁷-²², ²⁵-²⁸, ³¹, ³², ³⁴-³⁶, ⁴⁰, ⁴¹, ⁵⁰-⁵², ⁵⁴-⁵⁷, ⁶⁰, ⁶², ⁶³, ⁷⁰, ⁷²-⁷⁴, ⁷⁶-⁸⁰, ⁸²-⁸⁵, ⁸⁹-⁹³, ⁹⁵, ¹⁰¹)
Experimental	(¹⁶, ²³, ²⁴, ³⁷, ³⁸, ⁴³, ⁴⁴-⁴⁸, ⁶⁴-⁶⁶, ⁶⁸, ⁶⁹, ⁷⁵, ⁸⁷, ⁸⁸, ⁹⁴, ⁹⁶, ⁹⁸, ¹⁰⁰, ¹⁰³, ¹⁰⁴, ¹⁰⁷, ¹⁰⁸)
Case series	(²⁹, ³⁰)
Case study	- - - - -
Type of intervention
Direct	(¹⁴-²¹, ²³-³², ³⁴-⁵⁸, ⁶⁰-⁶⁶, ⁷⁰-⁷⁴, ⁷⁶-⁸⁹, ⁹¹, ⁹², ⁹⁴-⁹⁷, ⁹⁹, ¹⁰¹-¹⁰⁵, ¹⁰⁷-¹¹⁰)
Indirect	(²², ¹⁰⁶)
Both	(³³, ⁵⁹, ⁶⁷-⁶⁹, ⁷⁵, ⁹⁰, ⁹³, ⁹⁸, ¹⁰⁰)
TOTAL TIME OF INTERVENTION
Less than 1 minute	(¹⁴, ²³, ²⁶, ²⁷, ⁶⁰, ¹⁰³)
1-3 minutes	(¹⁵, ¹⁶, ⁴¹-⁴³, ⁴⁵, ⁸⁹)
4-10 minutes	(²⁰, ²⁹, ³⁵, ⁴⁰, ⁴⁴, ⁴⁵, ⁵⁰, ⁵², ⁷³, ⁸¹, ⁸², ⁸⁷, ⁹¹)
11-20 minutes	(³², ⁴⁸, ⁵¹, ⁵⁴, ⁸⁸, ⁹², ⁹⁷)
21-30 minutes	(¹⁵, ²⁵, ⁴⁶, ⁶¹, ⁶³, ⁶⁶, ⁷⁸, ⁹⁰, ⁹⁵, ⁹⁶, ⁹⁹, ¹⁰⁵, ¹⁰⁶)
31-40 minutes	- - - - -
41-60 minutes	(⁸³, ⁹³, ⁹⁴)
1 to 2 hours	(¹⁹, ²², ²⁸, ⁵³, ⁵⁵, ⁶⁷, ⁶⁹, ⁷⁵, ⁸⁰, ⁸¹, ⁹⁹, ¹⁰⁰)
2 to 5 hours	(²⁴, ⁴⁷)
More than 5 hours	(⁵⁹, ⁶⁸, ¹⁰², ¹⁰⁷)
Information not available	(¹⁷, ¹⁸, ²¹, ³⁰, ³¹, ³³, ³⁴, ³⁶-³⁹, ⁴⁹, ⁵⁷, ⁵⁸, ⁶², ⁶⁴, ⁶⁵, ⁷⁰-⁷², ⁷⁴, ⁷⁶, ⁷⁷, ⁷⁹, ⁸⁴-⁸⁶, ⁹⁸, ¹⁰¹, ¹⁰⁴, ¹⁰⁸-¹¹⁰)
NUMBER OF SESSIONS
Single session	(¹⁴, ²⁰, ²¹, ²⁴, ²⁶-³², ³⁵, ³⁶, ⁴⁰-⁵³, ⁵⁹, ⁶³, ⁶⁵,⁶⁹, ⁷⁰, ⁷³-⁷⁵, ⁷⁶, ⁷⁸-⁸⁵, ⁹², ⁹⁸, ¹⁰¹, ¹⁰³-¹⁰⁶, ¹⁰⁸)
2-4 sessions	(¹⁵-¹⁷, ¹⁹, ²², ²⁵, ³⁷, ⁵³, ⁵⁴, ⁷¹, ⁷², ⁸⁸, ⁸⁹, ⁹⁴-⁹⁶, ⁹⁷, ⁹⁹, ¹⁰⁹)
5-8 sessions	(¹⁷, ¹⁸, ³⁴, ³⁸, ⁵⁶-⁵⁸, ⁶⁶, ⁶⁸, ⁸⁶, ⁸⁷, ⁹⁴, ⁹⁷)
9-12 sessions	(⁶⁰, ⁶², ⁶⁷, ⁷⁵, ⁹³)
13-15 sessions	(¹⁰⁶, ¹⁰⁷)
8-16 sessions	(²³, ⁶⁷)
16-20 sessions	(⁹¹)
Information not available	(³³, ³⁹, ⁶¹, ⁶⁴, ⁷⁷, ⁹⁰, ¹⁰⁰, ¹⁰², ¹¹⁰)
MOMENT WHEN EFFECTS WERE ASSESSED
Immediately	(¹⁴, ²⁰, ²¹, ²⁴, ²⁶-³², ³⁵, ³⁶, ⁴⁰-⁵³, ⁵⁷, ⁵⁹, ⁶⁰, ⁶⁴, ⁶⁶, ⁷⁰, ⁷¹, ⁷³, ⁷⁴, ⁷⁶, ⁷⁸-⁸⁵, ⁹², ⁹⁸, ¹⁰¹, ¹⁰³-¹⁰⁶, ¹⁰⁸)
In follow-up	(¹⁵-¹⁹, ³⁴, ³⁷, ³⁸, ⁵⁶, ⁶¹-⁶³, ⁶⁵, ⁶⁷-⁶⁹, ⁷², ⁷³, ⁸⁶-⁸⁹, ⁹¹, ⁹³-⁹⁷, ⁹⁹, ¹⁰⁰, ¹⁰², ¹⁰⁷, ¹⁰⁹)
Information not available	(²², ²³, ²⁵, ³³, ³⁹, ⁵⁴, ⁵⁵, ⁵⁸, ⁵⁹, ⁷⁵, ⁷⁷, ⁹⁰, ¹¹⁰)
ASSESSMENT METHOD
Self-assessment	(¹⁵-¹⁸, ²², ²³, ²⁸, ³², ³³, ³⁸, ⁴⁵, ⁵³, ⁵⁵, ⁵⁸, ⁵⁹, ⁶³, ⁶⁶-⁶⁹, ⁷⁵, ⁷⁷, ⁷⁸, ⁸², ⁸³, ⁸⁷, ⁸⁸, ⁹¹, ⁹⁸-¹⁰⁰, ¹⁰³-¹⁰⁷, ¹⁰⁹, ¹¹⁰)
APE	(¹⁷-¹⁹, ³¹, ⁴⁶, ⁴⁸, ⁵⁸, ⁶¹, ⁷⁰, ⁷⁸, ⁷⁹, ⁸², ⁸⁸, ⁹¹, ⁹³, ⁹⁵, ⁹⁶, ⁹⁹, ¹⁰⁰, ¹⁰², ¹⁰⁶, ¹⁰⁷)
Acoustic	(¹⁴-¹⁷, ¹⁹-²¹, ²³, ²⁴, ²⁸, ³¹-³⁴, ³⁷, ³⁸, ⁴⁰, ⁴¹,⁴³-⁴⁶, ⁴⁸, ⁵³, ⁵⁴, ⁵⁶-⁵⁸, ⁶⁰-⁷¹, ⁷³-⁷⁸, ⁸¹-⁸³, ⁸⁶-⁸⁹, ⁹¹-⁹⁵, ⁹⁷-¹⁰³, ¹⁰⁵-¹⁰⁷, ¹⁰⁹, ¹¹⁰)
Laryngeal examination	(²¹, ²⁶, ³⁰, ³¹, ³⁵, ⁶⁵, ⁷⁹-⁸¹, ⁸⁸, ⁹³, ⁹⁵, ¹⁰⁰, ¹⁰², ¹⁰⁶, ¹⁰⁸)
Aerodynamics	(¹⁶, ¹⁸, ²⁰, ²⁷, ²⁹, ³¹, ³², ³⁷, ⁴⁴, ⁴⁶, ⁵⁴-⁵⁶, ⁶⁶-⁶⁹, ⁷¹-⁷³, ⁸⁰, ⁸², ⁸³, ⁸⁸, ⁸⁹, ⁹⁷, ⁹⁹-¹⁰¹, ¹⁰⁵-¹⁰⁷, ¹⁰⁹)
Others	(¹⁴, ²³-²⁷, ²⁹, ³², ³⁴-³⁶, ³⁹, ⁴⁰-⁴⁷, ⁴⁹-⁵², ⁵⁴, ⁵⁵, ⁵⁷, ⁵⁸, ⁶⁰, ⁶¹, ⁶², ⁷²-⁷⁴, ⁷⁶, ⁷⁹, ⁸³-⁸⁷, ⁸⁹, ⁹⁰, ⁹³, ⁹⁴, ⁹⁶, ¹⁰¹-¹⁰⁶, ¹⁰⁸-¹¹⁰)
TASKS
Sustained vowel in habitual tone	(¹⁴-¹⁷, ¹⁹, ²³, ²⁴-²⁷, ³³, ³⁴, ³⁵, ³⁷-³⁹, ⁴¹-⁴³, ⁴⁵, ⁴⁷, ⁴⁹, ⁵⁰, ⁵¹, ⁵³-⁵⁶, ⁶⁰, ⁶⁴, ⁶⁶-⁶⁸, ⁷⁰-⁷³, ⁷⁶, ⁷⁷, ⁷⁸, ⁷⁹, ⁸², ⁸³, ⁸⁵, ⁸⁷-⁸⁹, ⁹¹, ⁹⁵, ⁹⁷, ⁹⁸, ¹⁰⁰, ¹⁰⁵, ¹⁰⁶)
MPT emission (vowel or alveolar fricatives)	(¹⁸, ²⁵, ²⁸, ²⁹, ³³, ⁶⁶-⁶⁹, ⁷⁵, ⁸¹, ⁹¹, ⁹⁴, ¹⁰⁰, ¹⁰², ¹⁰⁵, ¹⁰⁶, ¹⁰⁸)
Sustained vowel at varied intensities	(²⁰, ²¹, ³³, ⁴³, ⁴⁵, ⁴⁶, ⁵¹, ⁶⁷, ⁸⁷)
Sustained vowel at varied frequencies	(³³, ³⁸, ⁴¹, ⁴³, ⁴⁶, ⁶⁵, ⁶⁷, ⁷¹, ⁸⁷, ⁹⁷, ¹⁰⁹)
Linked speech at varied intensities	(³¹, ⁹², ⁹³, ⁹⁹, ¹⁰⁴)
Linked speech at varied frequencies	(¹⁷, ²⁰, ²⁸, ⁴⁵, ⁴⁶, ⁴⁸, ⁵³-⁵⁶, ⁵⁸, ⁵⁹-⁶¹, ⁷⁰, ⁷³, ⁷⁶, ⁷⁸, ⁸³, ⁸⁴, ⁸⁶, ⁸⁸-⁹⁴, ⁹⁶, ⁹⁹, ¹⁰¹, ¹⁰⁴, ¹⁰⁸)
Singing tasks	(¹⁷, ²⁰, ⁴⁸, ⁵¹, ⁵⁷, ⁶², ⁶³, ⁷⁴, ⁸³, ⁸⁶, ⁸⁸, ⁹³, ⁹⁷, ⁹⁹, ¹⁰², ¹⁰⁷, ¹⁰⁹, ¹¹⁰)
Others	(²², ²⁹, ³⁰, ³², ³⁶, ³⁹-⁴⁶, ⁴⁹, ⁵¹, ⁵², ⁵⁹, ⁶², ⁶³, ⁷¹, ⁷², ⁷⁸, ⁸⁰, ⁸⁴, ⁸⁵, ⁸⁷, ⁹⁴, ⁹⁶, ¹⁰³, ¹⁰⁴)

VARIABLES	STUDIES INVESTIGATED
SAMPLE SIZE
Fewer than 30 participants	(¹⁴, ¹⁷-¹⁸, ²⁰-³², ³⁴-⁴³, ⁴⁵-⁴⁶, ⁴⁹-⁵⁸, ⁶⁰-⁶³, ⁶⁵-⁶⁶, ⁶⁸, ⁷⁰-⁷⁴, ⁷⁶-⁷⁷, ⁸⁰, ⁸², ⁸⁵-⁹⁶, ⁹⁹, ¹⁰¹, ¹⁰³-¹⁰⁴, ¹⁰⁷-¹⁰⁸)
30 - 60 participants	(¹⁵-¹⁶, ³³, ⁴⁴, ⁴⁷-⁴⁸, ⁶⁴, ⁶⁷, ⁶⁹,⁷⁸-⁷⁹, ⁸¹, ⁸³-⁸⁴, ⁹⁷-⁹⁸, ¹⁰⁰, ¹⁰², ¹⁰⁹-¹¹⁰)
60 - 90 participants	(¹⁹, ⁵⁹, ⁷⁵, ¹⁰⁵)
More than 90 participants	(¹⁰⁶)
SEX
Only males	(²⁷, ³⁶, ⁴¹-⁴³, ⁸⁶)
Only females	(¹⁸, ²⁰, ²³, ²⁸, ³¹, ³⁷, ⁴⁰, ⁴⁶, ⁴⁹, ⁵⁹, ⁶²-⁶⁴, ⁶⁷-⁶⁹, ⁷¹, ⁷³, ⁷⁴, ⁷⁷, ⁷⁸, ⁸², ⁸⁴, ⁸⁵, ¹⁰⁵-¹⁰⁷)
Predominantly males	(²¹, ²⁹, ³⁰, ⁵¹, ⁵⁷, ⁷⁹, ⁸⁷, ⁹², ⁹⁴, ¹⁰⁰, ¹¹⁰)
Predominantly females	(¹⁴, ¹⁷, ¹⁹, ²², ²⁵, ³², ³⁴, ⁴⁴, ⁴⁸, ⁵²-⁵⁶, ⁷⁰, ⁷⁸, ⁸⁰, ⁸¹, ⁸³, ⁸⁸, ⁹¹, ⁹⁶, ⁹⁹, ¹⁰²-¹⁰⁴, ¹⁰⁸)
Equivalent number between sexes	(¹⁵, ¹⁶, ²⁶, ³⁵, ³⁹, ⁵⁰, ⁵⁸, ⁶⁰, ⁶¹, ⁶⁶, ⁷², ⁷⁶, ⁸⁹, ⁹⁰, ⁹⁵, ⁹⁸, ¹⁰¹, ¹⁰⁹)
Information not available	(²⁴, ³³, ³⁸, ⁴⁵, ⁴⁷, ⁶⁵, ⁷⁵, ⁹³, ⁹⁷)
AGE OF THE PARTICIPANTS
Under 18 years old	(¹⁴)
Mean age between 18 - 25 years	(¹⁵, ¹⁶, ¹⁸, ¹⁹, ²², ³¹-³³, ³⁷, ⁴¹, ⁴³-⁴⁵, ⁶⁶-⁷⁴, ⁷⁷, ⁸⁰, ⁸⁴, ⁸⁷, ⁹⁰, ⁹⁷, ¹⁰⁰, ¹⁰², ¹⁰⁵, ¹⁰⁶, ¹⁰⁸, ¹¹⁰)
Mean age between 26 - 40 years	(¹⁷, ²⁰, ²¹, ²³, ²⁴, ²⁵-³⁰, ³⁵, ⁴², ⁴³, ⁴⁶-⁴⁸,⁴⁹, ⁵⁰-⁵⁵, ⁵⁷, ⁵⁸, ⁶¹-⁶⁴, ⁷⁵, ⁷⁶, ⁷⁸, ⁷⁹, ⁸¹, ⁸³, ⁸⁸, ⁸⁹, ⁹³, ⁹⁵, ⁹⁸, ¹⁰⁸, ¹⁰⁹)
Mean age between 40 - 60 years	(⁵⁹, ⁹¹, ⁹², ¹⁰¹, ¹⁰³, ¹⁰⁴)
Above 60 years old	(³⁴, ³⁸, ⁵⁰, ⁵⁶, ⁶⁰, ⁸², ⁹⁴)
Information not available	(³⁶, ³⁹, ⁴⁰, ⁶⁵, ⁸⁵, ⁸⁶, ⁹⁶, ⁹⁹, ¹⁰⁷)
OCCUPATIONAL VOICE USE
Occupational voice users	(¹⁷, ¹⁹, ²², ²⁶, ²⁸-³⁰, ³²-³³, ⁴⁶, ⁴⁸, ⁵⁷, ⁵⁹-⁶¹, ⁶⁶, ⁷³-⁷⁵, ⁷⁷, ⁸³-⁸⁵, ⁸⁷, ⁸⁸, ⁹¹, ⁹², ⁹⁹-¹⁰²)
Nonoccupational voice users	(¹⁴-¹⁶, ¹⁸, ²⁰, ²¹, ²³-²⁵, ²⁷, ³¹, ³⁴, ³⁷-⁴¹, ⁴⁴, ⁴⁵, ⁴⁷, ⁴⁹-⁵⁶, ⁵⁸, ⁶²-⁶⁵, ⁶⁷-⁷², ⁷⁶, ⁷⁸-⁸², ⁸⁶, ⁸⁹, ⁹⁰, ⁹³, ⁹⁴, ⁹⁶-⁹⁸, ¹⁰³, ¹⁰⁵-¹⁰⁸, ¹¹⁰)
Mixed samples	(³⁵-³⁶, ⁴², ⁴³, ⁹⁵, ¹⁰⁴, ¹⁰⁹)

[1] Caption: APE = auditory-perceptual evaluation; MPT = maximum phonation time

Measurements of the effect of interventions on heathly voices: a scope review

ABSTRACT