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Measurements of the Acoustic Speaking Voice After
Vocal Warm-up and Cooldown in Choir Singers
*Fernanda Onofre, †Yuka de Almeida Prado, *Gleidy Vannesa E. Rojas, *Denny Marco Garcia, and
*Lílian Aguiar-Ricz, *†Ribeirão Preto, Brazil
Summary: Objectives. The aim of this study was to evaluate the acoustic measurements of the vowel /a/ in modal
recording before and after a singing voice resistance test and after 30 minutes of absolute rest in female choir singers.
Study Design. This is a prospective cohort study.
Methods. A total of 13 soprano choir singers with experience in choir singing were evaluated through analysis of
acoustic voice parameters at three points in time: before continuous use of the voice, after vocal warm-up and a singing
test 60 minutes in duration respecting the pauses for breathing, and after vocal cooldown and an absolute voice rest
for 30 minutes.
Results. The fundamental frequency increased after the voice resistance test (P=0.012) and remained elevated after
the 30 minutes of voice rest (P=0.01). The jitter decreased after the voice resistance test (P=0.02) and after the 30
minutes of voice rest. A significant difference was detected for the acoustic voice parameters relative average pertur-
bation (RAP), (P=0.05), and pitch perturbation quotient (PPQ), (P=0.04), compared with the initial time point.
Conclusions. The fundamental frequency increased after 60 minutes of singing and remained elevated after vocal
cooldown and absolute rest for 30 minutes, proving an efficient parameter for identifying the changes inherent to voice
demand during singing.
Key Words: Singing voice–Acoustic analysis–Voice quality–Voice fatigue–Fundamental frequency.
INTRODUCTION
The voice performs a fundamental process in human relations
and in communication, transmitting a message by means of
speech, emotion, and expressivity. Physiologically, phonation
depends on muscle mechanisms of the entire body, especially
those that serve voice production, on the integrity of all tissues
of the phonatory apparatus, on inborn neurophysiological func-
tion, and also on the personality of an individual. These
mechanisms permit the production of a voice with a good sound
quality without difficulty or discomfort for the speaker. Con-
tinuous voice production is an activity that involves the
synchronized interaction of various physical processes such as
breathing, phonation, and resonance, requiring care to be
efficient.1–3
In addition to communication, the voice is also a working in-
strument for singers, actors, teachers, telemarketing operators,
lawyers, clergymen, and other professionals on intensive vocal
use. The negative effects of excessive vocal demands have been
evaluated for a variety of professions, each with its own
peculiarities.4–9
Hollien10 has stated that a “golden voice” can be the fruit of
talent and can be learned, especially for singing. Refined singing
is a multivariate task that depends on extensive study and train-
ing. Singers are expected to reach an optimum level of voice
production and performance with the execution of complex ma-
neuvers during phonation. This vocal competence for the
production of singing voice is based on the presence of a func-
tional, healthy, and aesthetically acceptable voice, as well as on
arduous training.2,11
Among singers, voice production is frequently affected by ex-
ternal environmental factors, and therefore, these professionals
are considered to be at risk of developing voice disorders. Thus,
accomplished singers should have knowledge about voice pro-
duction and should follow proper vocal training and validated
warm-up techniques.11,12
Vocal training is the main factor for the improvement of singing
voice. Mendes et al13 studied 14 major voices and found that vocal
training had a significant effect on singing voice, specifically on
fundamental frequency (F0) and sound pressure level, and em-
phasized that acoustic parameters can detect these changes.
In singing, the high voice demand at strong intensities and
with the very high notes often used and the different adjust-
ment of the vocal tract, producing a wide diversity of sound
effects, must generate physiological changes. Vocal training is
considered to cause the speaking voice of a singer to be differ-
ent from that of a nonsinger, and it is understood that the
efficiency, including the maximization of vocal frequency and
intensity, the optimization of voice quality, as well as the ability
to sustain tones for long periods of time, are the result of voice
training and of the experience of the singer.14
It is being questioned if singing training has an effect on the
spoken voice. Intuitively, it is being speculated that the contin-
uous training of a singer has an effect on his speaking voice
patterns. Trained singers use different physiological strategies
during singing compared with nonsingers,15–17 although singers
and nonsingers use similar respiratory maneuvers and laryn-
geal and/or articulatory movements during speech.16,17
Although some singers can produce perceptual distinctions
in their speaking voice, this change is poorly evident.18 Singing
training seems to be essential to affect and improve the singing
Accepted for publication December 2, 2015.
From the *Department of Ophthalmology, Otorhinolaryngology, Head and Neck Surgery,
Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil; and
the †Music Department, Faculty of Philosophy, Science and Letters of Ribeirão Preto, Uni-
versity of São Paulo, Ribeirão Preto, SP, Brazil.
Address correspondence and reprint requests to Lílian Aguiar-Ricz, Department of
Ophthalmology, Otorhinolaryngology and Head and Neck Surgery, Ribeirão Preto Medical
School, University of São Paulo, Av. Bandeirantes, 3900, Monte Alegre, 14090-900, Ribeirão
Preto, SP, Brazil. E-mail: liricz@fmrp.usp.br
Journal of Voice, Vol. 31, No. 1, pp. 129.e9–129.e14
0892-1997
© 2017 Published by Elsevier Inc. on behalf of The Voice Foundation.
http://dx.doi.org/10.1016/j.jvoice.2015.12.004
voice, although it rarely modifies the speaking voice.19 However,
Lundy et al20 observed that the singing voice of singing stu-
dents shows lower shimmer and harmonics-to-noise ratio values
than the speaking voice.
Constant vocal training together with effective warm-ups pre-
pares the phonatory apparatus for the requirements of singing
and helps prevent vocal fold injuries in voice professionals. Pro-
fessional singers and singing students consider a program of voice
warm-up to be essential. However, although voice warm-up has
long been used by singers, little is known about its impact on
the physiology of the vocal folds as well as the way it affects
the acoustic voice parameters.21–23
Different proposals are available for voice warm-up, most of
them involving alignment of body posture and relaxing exer-
cises, breathing exercises, and vocal production at different
frequencies, registers, and extensions.24,25 Elliot et al21 stated that
voice warm-up has an equivalent effect on the laryngeal muscles
as warm-ups do on other muscles. They reported that after voice
warm-up, the muscular temperature is increased and therefore
the viscosity of muscle tissue is reduced. They investigated the
effect of warm-up on the phonation threshold pressure in a group
of male and female singers and observed that all subjects ben-
efited from voice warm-up, concluding that there was a decrease
in the phonation threshold pressure, although with individual varia-
tions. The authors added that all singers participating in the study
felt that the quality of their voice was better after warm-up and
that they could sing with less effort and control their voice more
easily.
Muscular warming may be effective because as the temper-
ature of the muscles increase, resistance in the muscles and the
joints becomes reduce and elasticity improves, a greater release
of oxygen from hemoglobin and myoglobin contributes to muscle
oxygenation, metabolic activity accelerates, and there is an in-
crease in nerve conduction. There are also effects not related to
increased temperature such as increased blood flow to the muscle,
increased oxygen consumption, and muscle action potentials after
activation, including increased muscle contractility and reduced
fatigue, as well as psychological effects.26
Although it is widely accepted that warm-up improves vocal
production and facilitates phonation, very little is known about
the mechanism underlying the effect of the vocal warm-up. It
has been suggested that voice warm-up affects the physical char-
acteristics of the vocal folds by reducing vocal fold thickness
and by modifying the surface and wave velocity.21
Motel et al22 examined the effect of vocal warm-up in 10 so-
pranos and suggested that warm-up exercise can increase the
viscosity of the vocal folds and stabilize the voice. Amir et al23
emphasized that the vocal warm-up has a positive effect on voice
quality and that acoustic analysis is a valuable and sensitive in-
strument for the quantitation of this effect. Another aspect to be
considered is the awareness of which voice exercises are more
effective and more frequently used, as well as acknowledge the
ideal frequency and duration of voice warm-up sessions. The
warm-up schemes used in previous publications dealing with the
voice are quite varied, with a lack of comparable results in overall
literature. Some studies use standardized warm-up protocols, and
others use personalized protocols varying in terms of time.
Gishi et al25 evaluated 117 singers and observed that 54% of
the participants reported that they always do voice warm-ups
before singing. The preferred duration of the warm-up was 5–10
minutes. However, 26% of the participants reported to have voice
problems even when using voice warm-ups. Women used warm-
up more frequently and for a longer time than men. The exercises
most frequently used for warm-up without the use of singing
were stretching of the face, neck and shoulder muscles by 62%
of the participants, and breathing exercises by 55%. Scales of
five ascending/descending notes, scales of ascending/descending
octaves, arpeggio, legato, and glissando were more used for voice
warm-up.
It is known that an exaggerated vocal demand provokes vocal
fatigue. However, after years of classical music training, a singer
is expected to be able to produce a beautiful voice without effort
regardless of the requirements of his performance. Carroll et al27
evaluated semiprofessional and professional singers for a period
of two weeks leading up to a performance and observed the im-
portance of vocal rest: Carroll et al found that when a day of
high vocal demand was followed by 2 days of vocal rest, there
was a lower impact on the singer. In addition, a high demand
on consecutive days resulted in a cumulative effect of fatigue.
The healing of injuries provoked by a high vocal demand re-
quires an appropriate time for full tissue recovery. If the
requirements persist, the vocal folds will need practically con-
stant repair.28 Verdolini et al29 identified an increase of various
inflammatory mediators in the vocal folds after a high demand
exercise.
McHenry et al9observed opera singers before, during, and after
performances, suggesting that voice rest on the day after the per-
formance can facilitate voice recovery.
A review of the literature did not reveal any information on
the effects of a cooldown. On this basis, it should be kept in mind
that after the use of the singing voice, it is necessary to perform
voice cooldown with a time of rest to reestablish vocal tension,
preventing the persistence of the stress incorporated into singing.
Thus, the objective of the present study was to evaluate the
acoustic measurements of the vowel /a/ in a modal register before
and after a singing voice resistance test and after 30 minutes of
absolute voice rest in female choir singers.
METHODS
The study was approved by the Research Ethics Committee of
the institution (protocol no. 7716/2012), and all subjects gave
written informed consent to participate.
This was a prospective cohort study conducted on 13 soprano
choir singers aged 18–36 years with a mean choir singing ex-
perience of 9.69 years. Table 1 lists the data of the participants,
their age in years, vocal range, level of education, time of ex-
perience in years, and practice time in hours.
Singers with a history of dysphonia; previous diagnosis of gas-
troesophageal reflux; hormonal changes; a diagnosis of rhinitis;
diseases of the respiratory tract; and hearing, neurological, or
psychiatric disorders were excluded from the study. Regarding
habits, smokers and users of psychoactive substances or of con-
tinuous medications such as antihistamines, antidepressants, and
129.e10 Journal of Voice, Vol. 31, No. 1, 2017
antihypertensive, hypoglycemic or anti-inflammatory agents were
also excluded.
Procedures
For the study, individual afternoon appointments were sched-
uled with each singer always in the afternoon. The singers were
instructed to take their last meal 2 hours before the voice resis-
tance test to allow for gastric emptying and thus prevent gastric
reflux up to the larynx region. The singers were asked not to ingest
foods such as citrus fruit, tomatoes, onions, spicy, fat or fried foods,
sweets or chocolate, and to avoid carbonated or caffeinated drinks.
On the day scheduled, before starting the singing voice re-
sistance test, the participants performed voice warm-up for a
previously established period of 10 minutes, singing the vowel
that they usually exercise in vocalization, up and down every
half tone of a vocally comfortable more grave note to the most
acute one while being accompanied by the sound of a Yamaha®
keyboard model PSR E403 (Yamaha Corporation, Brasil)
(Figure 1)
After voice warm-up, the participants were instructed to sing
continuously for up to 60 minutes, always with respiratory pauses
to prevent any voice discomfort, the motet Ave Verum Corpus,
with a vocal extension from Re3 to Mi4, by Wolfgang Amadeus
Mozart (1756–1791), previously selected taking into consider-
ation the knowledge and training of the choir singers. The
performance was tracking a playback with the recording of the
song lasting 1‘58, being repeated from start to finish without in-
terruption, until the maximum time that the singer could run it,
an average of 30 repetitions. Each participant sang in the key
appropriate to her range, ie, for her voice classification as a
soprano. After singing for up to 60 minutes, the singers re-
mained in absolute silence for 30 minutes.
TABLE 1.
Characterization of the Soprano Choir Singers: Age, Voice Extension, Description of Singing Formation, Time of Expe-
rience, and Time of Training per Week
Choir
Singer
Age
(Years)
Voice
Extension
Formation
in Singing
Time of Choir
Experience (Years)
Singing Practice per
Week (Hours)
1 28 A2–A5 Graduation in music 5 10
2 33 G2–C5 Graduation in music 16 8
3 26 G#2–C5 Choir 14 14
4 22 G#2–E5 Choir 7 7
5 24 G#2–D5 Graduation in music 15 9
6 33 G#2–G4 Choir 20 1
7 24 B2–D#5 Choir 9 8
8 30 G#2–C#5 Graduation in music 10 8
9 24 G#2–F4 Graduation in music 9 8
10 21 B2–E5 Graduation in music 4 3
11 22 B3–C5 Graduation in music 4 6
12 27 G#2–D#5 Graduation in music 7 10
13 24 B2–F5 Graduation in music 6 14
FIGURE 1. Vocalization used in voice warm-up. Two singers sang with the vowel /i/; 1 singer sang with the vowels /i/ /u/; and 10 singers sang
with the vowels /a/ /i/.
Fernanda Onofre et al Voice After Vocal Warm-up and Cooldown in Choir Singers 129.e11
For the analysis of the vocal register, the singers recorded the
prolonged emission of the vowel /a/ in their habitual modal register,
and vocal intensity and frequency three consecutive times in the
following situations: before (basal), after the 60 minutes of singing
voice resistance test (singing test), and after 30 minutes of abso-
lute voice rest (rest) following the test. The singers used a Samson®
(Samson Technologies, New York, USA) unidirectional micro-
phone G-Track GM 1U USB, with recording by the SoundForge
6.0®software (Sony Pictures Digital Inc®) at a sampling rate of
44,100 Hz and 16 bits,stored in the wav format on a computer
equipped with an Intel®processor. The procedure was carried out
in an acoustically treated room with noise kept below 50 dB as
measured by a digital decibel meter.
The most stable sound signal was visually extracted from the
stored voice sample, discarding the beginning and the end of the
emission due to their irregular characteristics and selecting best
sound signal having at least 3 seconds of sound production.
The Multi-Dimensional Voice Program of the Computerized
Speech Lab software/model 6103 of Kay Pentax®was used to
extract the acoustic voice parameters: fundamental frequency (F0),
percent jitter (Jitt), relative average perturbation (RAP), pitch
perturbation quotient (PPQ), percent shimmer (Shim), ampli-
tude perturbation quotient (APQ), noise-to-harmonics ratio (NHR),
voice turbulence index (VTI), and soprosity index (SPI). The
acoustic measurements were made at three time points, ie, basal,
effort, and rest.
Statistical analysis
Descriptive (mean ±standard error) and inferential analyses of
the data were carried out for statistical analysis. The mean values
obtained at the three different time points were compared by uni-
factorial analysis of variance with repeated measures. When
significant differences between means were detected, the Tukey-
HSD (honest significant differences) post hoc test was used for
multiple comparisons. The analyses were performed using the
Origin Pro 9.0 software (OriginLab, Northampton, MA), with
the level of significance set at 5%.
RESULTS
The acoustic voice parameters obtained from the analysis of the
sustained emission of the vowel /a/, modal register, before the
voice resistance test (basal), 60 minutes after the voice resis-
tance test and after 30 minutes of absolute voice rest (rest) are
listed in Table 2.
The F0 increased after the voice resistance test and after the
voice rest (Figure 2) and Jitt decreased after the voice resis-
tance test. When the results for the 13 singers were compared
before the singing test and after 30 minutes of voice rest, a sig-
nificant difference was detected for the acoustic voice parameters
RAP and PPQ, whereas no significant differences were ob-
served for the remaining acoustic parameters between the basal,
singing test, and rest time points (Table 2).
DISCUSSION
Singers are professionals at high risk for voice disorders. To
prevent voice problems, it is necessary to work with the pro-
motion of the singing voice. Vocal warm-up is believed to prepare
TABLE 2.
Acoustic Voice Parameters Obtained in the Spoken Emission of the Sustained Vowel /a/, Before (Basal) and 60 Minutes After the Singing Voice Resistance
Test (Singing Test), and After an Absolute Rest of 30 Minutes (Rest)
Acoustic Voice Parameters
Prevoice Resistance Rest
(Basal)
Postvoice Resistance Test
(Singing Test)
Vocal Rest
(Rest)
PValueRange Mean ±SE Range Mean ±SE Range Mean ±SE
Fundamental frequency F0 (Hz) 190.01–260.63 225.96 ±5.54 200.33–285.51 244.04 ±7.19 186.43–284.38 242.94 ±8.53 P= 0.007
Pre–post = 0.012*
Pre–rest =0.01*
Percent jitter (%) 0.29–2.42 1.08 ±0.19 0.22–1.74 0.58 ±0.11 0.21–1.44 0.67 ±0.09 P= 0.02
Pre–post = 0.02*
Relative average perturbation (RAP) (%) 0.25–1.45 0.71 ±0.11 0.21–1.05 0.50 ±0.06 0.20–0.86 0.485 ±0.05 P= 0.03
Pre–rest =0.05*
Pitch perturbation quotient (PPQ) (%) 0.24–1.42 0.74 ±0.10 0.24–1.04 0.59 ±0.06 0.22–0.89 0.53 ±0.05 P = 0.04
Pre–rest =0.04*
Percent shimmer, Shim (%) 1.30–5.64 2.86 ±0.35 1.07–4.96 2.59 ±0.35 1.46–5.79 2.55 ±0.31 P=0.70
Amplitude perturbation quotient (APQ) (%) 0.88–4.25 2.44 ±0.26 0.84–23.61 5.31 ±1.80 1.14–4.17 2.58 ±0.26 P= 0.10
Noise-to-harmonics ratio (NHR) (n) 0.02–0.13 0.09 ±0.01 0.02–8.19 1.21 ±0.78 0.02–0.15 0.08 ±0.01 P= 0.15
Voice turbulence index (VTI) (n) 0.01–27.55 3.73 ±2.14 0.02–25.40 5.17 ±1.92 0.02–8.45 3.21 ±1.01 P= 0.63
Soprosity index (SPI) 0.13–19.08 6.98 ±1.76 0.0.–16.71 2.51 ±1.37 0.17–22.12 7.22 ±2.34 P= 0.17
*Pvalue ≤0.05. Repeated measures analysis of variance (Tukey posttest—HSD).
129.e12 Journal of Voice, Vol. 31, No. 1, 2017
the phonatory apparatus for the requirements of singing and to
help prevent injuries to the vocal folds of voice professional.
However, there has been a reduced scientific investment regard-
ing the impact of the vocal warm-up on the physiology of the
vocal folds as well as on how warm-ups affect the acoustic pa-
rameters of the speaking and the singing voice.21–23
The voice warm-up is known to prepare the phonatory ap-
paratus for the requirements of singing, also contributing to the
prevention of injury to the vocal cords of voice professionals.
However, there has been little scientific investment in the study
of the effect of voice resistance during singing and of the cooldown
on the physiology of the vocal cords, and there has been debate
in the literature about how voice warm-up affects the acoustic
vocal parameters of the speaking and the singing voice.21–23
Lyrical singers may be compared to elite athletes and must
prepare to perform their artistic activity without losing the con-
dition of vocal health. In the present study, the vocal frequency
was found to remain high after the singing test, indicating that
the musculature remained stretched, with increased tension and
vibration of the vocal fold mucosa, suggesting that voice warm-
up was maintained throughout the singing test. The analysis of
the acoustic parameters has been shown to be a valuable tool
for the quantitation of the effect of voice warm-up.23
Bishop26 has stated that muscle warm-up may result in in-
creased blood flow to muscle, greater muscle elasticity, increased
oxygen consumption, and increased muscle contractility and can
produce psychological effects. The warming of skeletal muscle
provides increased blood circulation by opening and dilating the
blood capillaries of the muscle, this perhaps being the explanation
for the significant increase in F0 observed here after the singing
test. The natural length of the vocal fold, elongation, vibrating mass,
and tension all determine the F0. Thus, we infer that from a phys-
iological viewpoint, there was muscle stretching and increased
tension after the continuous singing test. The musculature, aided
by the joints, becomes more elastic and able to elongate, favoring
a decrease of elastic and viscous resistance, thus reducing the at-
trition between the vocal folds. For the performance of the speaking
voice, after singing, the muscles should return to their original
status, and therefore it is necessary to determine the best conduct
to be followed by singers after their performance. In the literature
reviewed for the present study, no studies were found reporting
results regarding the questions of absolute voice rest and/or exercise
programs. It is important to obtain this information for the pre-
vention of voice problems and for the longevity of the singing voice.
By warming up the muscles of the phonatory apparatus, singers
integrate the respiratory, laryngeal, and resonance systems, avoid-
ing unnecessary effort and overload.1,2 Different proposals are
available for voice warm-up, such as alignment of body posture,
relaxation exercises, breathing exercises, and vocal production
at different frequencies, registers, and extensions.24,25
Before singing the motet, the sopranos performed voice warm-
up for 10 minutes and then sang for up to 60 continuous minutes
so that their performance in the singing test would occur at the
highest limit of their capacity, favoring the chords necessary for
the execution of the musical notes and the adjustments of
minimum (pianissimo) and maximum (fortissimo) sound inten-
sity covering the vocal extension from the Re3 note to the Mi4
note. Mendes et al13 reported that vocal training results in a sig-
nificant effect on the singing voice, specifically on the F0. The
increased F0 observed here after singing agrees with the data
reported by the cited authors. The warm-up exercise may in-
crease the viscosity of the vocal folds and stabilize the voice of
sopranos,22 affecting the physical characteristics of the vocal folds,
such as a reduction of vocal fold thickness and a modification
of the surface and of wave velocity.21
The present results suggest that a voice rest is not sufficient
for the muscles of the vocal folds to return to their modal state.
Further experimental investigations are needed, with vocal ex-
ercises and techniques for cooldown of the muscles used for
singing voice performance. Voice cooldown must reduce muscle
tension, reducing the probability of injury and favoring tissue
regeneration for a new musical performance. Verdolini et al29
pointed out that the healing of injuries provoked by a high voice
demand requires time for regeneration.
Vocal training improves the singing voice but seldom modi-
fies the speaking voice.19 In the present study, there was an increase
in F0 after singing that was maintained after an absolute rest of
30 minutes regarding the vowel /a/ in a modal register. Lundy
et al20 also reported that the singing voice has a lower shimmer
and NHR than the speaking voice among singing students.
There is concern about the return of the vocal register of singers
at the end of each vocal performance. Many singers go out to
celebrate with colleagues after a performance and the use of the
speaking voice during the celebration may have harmful results
for their phonation. For this reason, in the present study, we opted
to analyze the emission of the vowel /a/ in the modal register
to understand the effect of singing and of voice cooldown on
the speaking voice. We observed that remaining silent for 30
minutes after singing did not favor the return of the speaking
voice to its original (basal) state.
The comparison of the results obtained before and after the
singing voice resistance test revealed that the Jitt parameter was
decreased. This parameter measures the irregularity of pitch on
a short-term basis (cycle to cycle) and reflects the instability of
the vocal folds in maintaining periodic vibration within a defined
time interval.
FIGURE 2. The results of fundamental frequency (Hz).
Fernanda Onofre et al Voice After Vocal Warm-up and Cooldown in Choir Singers 129.e13
There was a reduction of RAP and PPQ values after the singing
voice resistance test compared with the values obtained after a
voice rest of 30 minutes. In view of these data, we infer that there
was no change in the regularity of the glottic cycles and that this
result may perhaps be an indicator of the resistance of the vocal
cord muscles. Muscle resistance may be probably acquired by
means of successive musical performances. Voice cooldown may
help the muscles to recover more rapidly for successive perfor-
mances without successive traumas to the epithelium or fatigue
of the vocal fold muscles. If the requirements persist, the vocal
cords will need practically constant repair.28
Even among singers who perform voice warm-up, 26% report
voice problems,25 which may be due to lack of voice cooldown.
After singing, there is the need to rest9to reduce the stretching
of the intrinsic and extrinsic muscles of the larynx and to permit
the vocal folds to recover and to return to their basal state.28
Singers should use accepted techniques and avoid voice abuse
and should learn about voice production and be aware of warm-
up techniques.11,12
Carroll et al27 studied the singers over a period of 2 weeks
before a performance and observed the importance of voice rest.
Voice cooldown by maintaining absolute voice rest does not
reduce the F0, thus, 30 minutes of rest apparently were not suf-
ficient to reduce F0. McHenry et al9studied opera singers before,
during, and after a performance and recommended voice rest to
facilitate recovery. Perhaps, the time of voice rest indicated in
the present study was not sufficient to promote voice cooldown.
Or voice cooldown may not be promoted by absolute voice rest
but specific techniques should be indicated to reduce F0 and thus
favor the shortening of the vocal folds and the reduction of tension
to reestablish vocal tension and to prevent the permanence of
the muscle stress incorporated into singing.
Voice rest is important to prevent fatigue.27 Few singers use
voice cooldown,25 and the lack of this practice after the contin-
uous effect of muscle tension after singing may lead to a reduced
tessitura, a loss of flexibility in changing register, difficulty in
the production of strong and weak sounds, and instability of the
singing voice followed by instability of the speaking voice.
However, further studies are needed regarding the effects of
the singing voice resistance and vocal cooldown on the singing
voice and the increased vocal demand to extend scientific evi-
dence and to provide guidance for these professionals.
CONCLUSIONS
Analysis of the acoustic voice measurements of choir singers
submitted to a continuous singing test for up to 60 minutes fol-
lowed by absolute rest revealed that the F0 increased after singing
and remained elevated after voice cooldown with a 30 minute
rest, proving to be an efficient parameter for the identifying of
the changes inherent to the vocal demand of singing.
A reduction of RAP and PPQ was detected at the end of the
vocal rest compared with the initial measurement before the in-
tensive use of the singing voice, as well as a reduction of Jitt,
which improved after the vocal effort. On this basis, we suggest
that more studies should be conducted regarding voice warm-
up and cooldown to reduce the risks and attenuate the adverse
effects of vocal health in professional singers.
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