Table 4.

Definitions of vocal load in the included publications

#	Last Name, Year, Country	Definition of vocal load (vocal demand response)
1	Anand et al., 2019, USA	Alteration or modification in the combination of the three vocal parameters: fundamental frequency, intensity, and voice quality for a duration relatively less than 30 minutes
2	Jeremy et al., 2019, USA	Dose of time, dose of cycle, dose of distance, conditions of a place (room, living room), excessive noise and habits that add to health conditions that affect the vocal quality of a person
3	Okşan et al., 2020, Turkey	Use of the voice for long periods of time with a close relationship in cricoarytenoid constriction and stiffness
4	Ali et al., 2020, India	Prolonged use of voice
5	Swathy et al., 2017, India	Extensive use of the voice. Voice acoustic parameters used are fundamental frequency, disturbance measurements (jitter and shimmer), intensity (SPL) and harmonic ratio to noise during a workday
6	Xue et al., 2018, China	Several intrinsic factors, such as the duration of voice use, intensity of voice production, fundamental frequency. Extrinsic factors, such as room acoustics and ambient noise
7	Herndon et al., 2017, USA	Included aspects such as hydration level, background noise, vocal tone, and intensity
8	Rollins et al., 2019, USA	Vocal effort made according to environmental and organizational conditions to modify the voice in a communication context
9	Astolfi, 2018, Italy	Consequence of prolonged voice use under critical conditions, with contextual factors such as the number of people to be addressed and environmental factors, which generates a tendency to increase the loudness
10	Schiller et al., 2017, Belgium	Number of vocal demands for the phonatory system. Possibly determined mainly by the sound pressure level of the voice (SPL), fundamental frequency (FO) and phonation time
11	Pirilä et al., 2017, Finland	Occurs when a speaker unconsciously reacts to a noisy environment by changing the behavior of his voice
12	Mahalakshmi et al., 2018, India	Pollution of the environment, changes in temperature, energy, and noise, which the speaker must overcome by modifying his voice projection
13	Whitlinget al., 2016, Sweden	Vocal loading is said not only to be dependent on long phonation time at high intensity levels, but also appears to be dependent on long phonation time at high fundamental frequencies
14	Brinton et al., 2016, USA	The vocal load produces adverse changes in the aerodynamic, acoustic and perception measures of the listener, at the level of self-perceptual measures, which are related to vocal fatigue and has a significant impact on phonation
15	Boaz et al., 2015, Israel	Prolonged and intense use of the voice
16	Lima et al., 2015, Brazil	Use of the voice for long periods of time combined with internal and external factors of the participants
17	Puglisi et al., 2015, Italy	Related to room acoustics and noise in busy environments. Vocal load is also related to the time of the day, subject taught and number of students to whom voice is projected
18	Durup et al., 2015, Great Britain	Defined as related with the context and noise exposure
19	Cortes et al., 2014, Brazil	Use of the voice for a long time responding to an environment and its needs
20	Franca et al., 2014, USA	As excessive vocal use
21	Remacle et al., 2013, Belgium	The amount of voice that is used to perform in different scenarios. Vocal load is likely to contribute to the development of vocal fold damage due to potentially damaging tissue exposure to repeated vibrations
22	Acurio et al., 2014, Chile	Combination of prolonged use of the voice and additional factors, such as background noise, acoustics, and air quality, which affect the fo, mode and intensity of phonation, as well as the external frame of the larynx
23	Kankare et al., 2013, Egypt	It is the impact stress (force per unit area) that has been considered as the main load factor in the production of voice and has been reported to increase with adduction, the frequency fundamental (fo) and sound pressure level (SPL)
24	Franca, 2012, USA	Vocal loading is said not only to be dependent on long phonation time at high intensity levels, but also appears to be dependent on long phonation time at high fundamental frequencies
25	Astolfi et al., 2012, Italy	Amount of voice that the speakers make overtime
26	Remacle et al., 2011, Belgium	Acoustic vocal power integrated over time. The duration and the level of voice intensity are two knowns as load factors
27	Gaskill et al., 2011, USA	Accumulation of load that is due to prolonged time using the voice
28	Bottalico et al, 2011, Italy	Amount of voice over time
29	Morrow and Connor, 2010, USA	Demand placed on the vocal apparatus, due to the needs of the voice use, implying an integral calculation of the total phonation time and the total distance traveled by the vocal folds during their oscillation
30	Morrow and Connor, 2010, USA	Amount of vocal work quantify by the vibration of the vocal folds during phonation, including the phonation time, the fundamental frequency, and the amplitude of vibration of the vocal folds
31	Bottalico et al., 2010, Italy	Using your voice for long periods
32	Lei et al., 2020, Canada	Prolonged use of the voice in different tasks, imposing changes in its performance
33	Echternach et al., 2020, Germany	Use of the voice in diverse types of tasks at a given time, reflecting changes in the left and right symmetry, the opening and closing dynamics in the vocal folds, the vocal load being important for the health of the voice
34	Sundarrajan et al., 2017, India	Duration of voice production considering the environment, it is also seen in the use of voice tasks that stress the larynx and compromise its function
35	Abi and Santosh, 2020, India	Referred to stress conditions that challenge proper laryngeal functioning, leading to changes and physiological limits through the manipulation of external and internal factors
36	Pacheco and Behlau, 2018, Brazil	Using your voice for long periods
37	Whitling et al., 2014, Sweden	Combination of prolonged use of the voice with added load factors, such as high phonation at high sound pressure levels
38	Järvinen and Laukkanen, 2015, Finland	Result of a combination of factors in the excessively prolonged use of the voice, the high tone and intensity and a type of pressed phonation, implying a greater impact tension in the tissue of the strings vowels
39	Fornhammar et al., 2020, Germany	Using your voice for extended periods or at extremely high pitches
40	Echternach et al., 2013, Germany	Time of production of the voice for prolonged periods of time giving demand to a context or a situation
41	Grillo et al., 2016, USA	Continuous repetition of postures of the vocal folds or excessive vibration of the tissues, especially in people who use their voice in a professional way, due to an intense high of vocal activity
42	Nacci et al., 2013, Italy	Combination of prolonged use of the voice and additional load factors (background noise, acoustics, air quality) that affect the fundamental frequency, the type and volume of phonation and the vibratory characteristics of the vocal folds
43	Remacle et al., 2014, Belgium	Amount of work done by the laryngeal mechanism over time, determined mainly by the duration, intensity, and frequency of the vocalization
44	Enflo et al., 2013, Sweden	Intensive and prolonged use of the voice without rest, including phonotraumatic behaviors
45	Mozzanica et al., 2017, Switzerland	Intensive use of the voice for an extended period of time
46	Lira et al., 2014, Italy	Combination of the duration of use of the voice and the environmental characteristics
47	Soedersten et al., 2014, Sweden	Long-term prolonged use of the voice including vocal symptoms
48	Delgado et al., 2017, Spain	Abuse of the qualities of the voice for very long periods of time
49	Ternström et al., 2016, Sweden	Abuse and misuse of the voice for extended periods of time
50	Buckley et al., 2014, Australia	Using your voice for extended periods of time
51	Lyberg et al., 2014, Belgium	Increased activities in voice function including increased SPL and decreased jitter and brightness
52	Phyland et al., 2014, USA	Effect of increasing the loudness and/or tone in the vocal folds, generating increased vibratory amplitude, describing phonatory activities at levels higher than usual
53	Szabo et al., 2013, Sweden	Use of the voice at elevated levels of fundamental frequency and phonation time during work, including comparisons with free time
54	Hanschmann et al., 2010, Germany	Exposure of the voice for extended periods, experienced by people with greater professional use of the voice