Journal of Laryngology and Voice

: 2018  |  Volume : 8  |  Issue : 1  |  Page : 19--23

Effect of circadian cycle on voice: A cross-sectional study with young adults of different chronotypes

Thomas Zacharia1, Preema D'souza1, Minton Mathew1, Gwendalene D'souza1, Judith James2, Manjeshwar Shrinath Baliga3,  
1 Father Muller College of Speech & Hearing, Kankanady, Mangalore, Karnataka, India
2 Speech Language Pathologist, Mangalore Institute of Oncology, Kankanady, Mangalore, Karnataka, India
3 Father Muller Research Centre, Kankanady, Mangalore, Karnataka, India

Correspondence Address:
Dr. Manjeshwar Shrinath Baliga
In Charge of Research, Mangalore Institute of Oncology, Mangalore - 575 002, Karnataka


Background: Circadian rhythm (CR) which is termed as the “physical, mental, and behavioral changes that follow a roughly 24 h cycle responding primarily to light and darkness in an organism's environment” has an important role in human health. A literature study indicates that there are no studies addressing the effect of CR on voice. The current study was conducted to understand the effect of CR on voice, pitch, jitter and shimmer in healthy young adults. Methodology: The study consisted of 216 participants (98 males and 118 females). The volunteers were asked to fill the Horne–Ostbery Morningness-Eveningness Scale questionnaire followed by an acoustic analysis using the voice analyzing software PRAAT using a dynamic unidirectional microphone at four time points of the day (morning [7.30–8.30 am], mid-day [12.30–1.30 pm], early evening [4.30–5.30 pm] and night [8.30–9.30 pm]). Results: The results of the current study indicate that the CR has got a very strong relationship with jitter, pitch and shimmer in the voice and how these parameters vary across evening type, intermediate type, and morning type through the day. Conclusions: The findings of the current study are very important for professional voice users as they can select their time slot for the performance based on their CR and be effective in their duties/job.

How to cite this article:
Zacharia T, D'souza P, Mathew M, D'souza G, James J, Baliga MS. Effect of circadian cycle on voice: A cross-sectional study with young adults of different chronotypes.J Laryngol Voice 2018;8:19-23

How to cite this URL:
Zacharia T, D'souza P, Mathew M, D'souza G, James J, Baliga MS. Effect of circadian cycle on voice: A cross-sectional study with young adults of different chronotypes. J Laryngol Voice [serial online] 2018 [cited 2019 Sep 17 ];8:19-23
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Circadian rhythm (CR) which is a termed as a biological process that displays an endogenous, entrainable, oscillation of about 24 h is driven by a circadian clock and sleep is an important aspect for humans and animals.[1] From a physiological perspective, the internal clock or the biological clock controls all the CRs in humans and influences the neurobehavioral, hormonal, physiological, and behavioral functions.[1] Anatomically, the master pacemaker of the biological clock is present in the suprachiasmatic nucleus of the hypothalamus and entrains peripheral clocks using a wide range of signals.[2] From a health viewpoint, CR plays a vital role in the optimal health of the individual and its alterations for extended periods leads to various ailments.[2]

In humans, ideas, emotions, and feelings are conveyed through speech. For speech to be effective, the quality of voice is very important for both individual conveying the thoughts and to the listener who has to understand it. Voice is a multidimensional series of measurable events and is defined as the “laryngeal modulation of pulmonary air streams which is subsequently modified by the configuration of the vocal tract.”[3] Ideally, a good voice should have a pleasing voice quality, proper balance of oral and nasal resonance, appropriate loudness, a speaking fundamental frequency level suitable for the age, sex, and size and appropriate voice inflection involving pitch and loudness.[4]

Physiologically, the generation of voice is a complex process and involves many steps and the involvement of sub organs in the head-and-neck region (especially vocal cord, vocal tract, and tongue), resonatory and respiratory systems play a cardinal role toward the result.[5],[6] Studies have shown that the mobility of the vocal folds is regulated by the biomechanical properties of the fold itself, magnitude of the sub glottis air pressure, and the neural control.[7] Variation in any of these parameters due to any anatomical, structural and/or functional changes to the larynx, respiratory, resonatory, and articulatory systems beyond normal range can affect the phonation and voice quality.[5],[6]

CR has been observed to have myriad physiological functions and innumerable studies have now shown that disruption of CRs causes the loss of productivity, health risks such as increased propensity for cancer, depression, sleep disturbances, gastrointestinal disorders, metabolic and cardiovascular disorders, decreased immune response and life span, glucose intolerance, diabetes, and hypertension.[2],[8] However, there have been minimal studies to address whether CR affects the voice. A literature study indicated that there has been only one study that investigated the amount of variation for several vocal parameters across three times of the day (morning, noon, and afternoon) in healthy individuals by focusing only on the speaking fundamental frequency.[9]

In recent years, people have been realizing the importance of voice for their professional and personal life. Reports also indicate that nearly 6%–10% of the population has got some voice problems[10] and in this scenario, it is essential that one has to focus and study in detail all the aspects of it. A person who does not depend on his/her voice for a livelihood just ignores the signs and symptoms of voice problems. Professional voice users are typically in touch with their voice and are at risk of developing any voice problems. In these conditions, the speech-language pathologist and researchers have a vital role to play in assisting the professional voice users. Instead of these observations, the current study was planned considering the collection of data on the chronotype and the voice parameters across a single day at four important time points (morning, midday, evening, and late evening).


This was a prospective cross-sectional study and was conducted at Father Muller College of Speech & Hearing from November 2012 to February 2013. The students of medical, nursing, homeopathy, and allied health sciences were included in the study. The students were between the age group of 18–23 years. The inclusion criteria included people who were healthy and did not have a severe cold, diabetes, elevated blood pressure, known cases of voice pathology, who were chronic alcoholics, smokers, and tobacco chewers. Teachers, musicians, and singers were excluded from the study. The study was approved by the Institutional Ethics Committee and was carried out in accordance with the Helsinki guidelines for research on humans.

The PRAAT was used because it was a flexible tool to do speech analysis[11] and was available for the student investigators in the speech laboratory. The Horne–Ostbery Morningness-Eveningness Scale questionnaire (MEQ)[12] was selected because it is easy to administer and one of the widely used questionnaires to ascertain the circadian typology of an individual. The questionnaire consist of 19 questions regarding an individual's circadian typology like wakeup times and bedtimes; most appropriate times for physical and mental activities, and also on the state of consciousness before going to bed and immediately after waking.

Of the 19 questions, 10 are answered on a 5-point scale, and 9 are multiple-choice questions with a score range of 1–4 points. The sum of all the answers is the MEQ score and can range from 16 to 86. Depending on the total MEQ score, the circadian typology is classified as definitely morning type (70–86 points), moderately morning type (59–69 points), intermediate type (42–58 points), moderately evening type (31–41 points), and definitely evening type (19–30 points). For the study purpose, the scores of 41 and below indicate “evening types,” while that >59 indicate the “morning types,” scores between 42 and 58 indicate “intermediate types.”[12]

Before initiation of the study, one of the student investigators (TZ or PD) addressed the students and explained the purpose, aim, and importance of the study. They also informed the students that their participation was voluntary. Medical history was taken for all the participants to make sure that, all willing students satisfied the inclusion criteria. They were then provided with the MEQ and informed consent to be filled signed and returned during the proposed voice recording.

The volunteers were requested to come to the voice laboratory for voice recording at the designated time period in the day (morning [7.30–8.30 am], midday [12.30–1.30 pm], early evening [4.30–5.30 pm], and night [8.30–9.30 pm]). The acoustical voice analysis was carried out using the voice analysis software PRAAT (version 5.1.37; Phonetic Sciences, University of Amsterdam, Spuistraat 210, 1012VT, Amsterdam, The Netherlands]) using a Dynamic unidirectional AUD-59 XLR microphone which was kept 5 cm away from the mouth using a scale in a soundproof voice laboratory. Participants were asked to take a deep breath and phonate the vowel/a/for at least 20 s at four time points morning (7.30–8.30 am), midday (12.30–1.30 pm), early evening (4.30–5.30 pm), and night (8.30–9.30 pm) the same day. The initial and the final part of the recording was not considered for analysis due to the instability. Only the most stable phonation was considered for analysis. Due to the variation in phonation across participants, a specific time frame could not be considered. The participants were asked to phonate only the sound/a/.

Statistical analysis

The data obtained (MEQ and the voice parameters) was entered in the Microsoft Excel 2013 version and then analyzed using SPSS (Version 31, SPSS Inc., Chicago, Illinois, USA). Voice was analyzed across the various time points depending on the gender and chronotype. Analysis of variance was used to compare the extent of change in the voice parameter in the three chronotypes at each time point. A value of P < 0.05 was considered to be statistically significant.


The student investigators addressed around 556 students and only 266 students volunteered and completed the study. The volunteers were aged between 18 and 27 years with a mean age of 21.35 ± 2.37. A total of 98 males and 118 females completed the study. The results of the study are categorized as in males and females and are expressed in [Figure 1], [Figure 2], [Figure 3].{Figure 1}{Figure 2}{Figure 3}


The results indicate that in the females the peak jitter was observed at evening in the early and mid chronotypes, while in the late chronotypes, it was at morning (8.30–9.30 am). However, in males, it was observed that in late and early chronotypes the jitter was more in the morning (8.30–9.30 am) (P = 0.03), whereas in the mid chronotypes, it was in the evening (4.30–5.30 am) [Figure 1].


With respect to the females, the pitch was observed to be high in the late chronotypes in the evening (4.30–5.30 am) (P = 0.035), whereas it was high in the early and mid in the morning (8.30–9.30 am). On the contrary, in males, the pitch was observed to be high in the early (P = 0.04) chronotypes at night, evening in the late chronotypes and almost equal at both morning and night in the mid chronotypes [Figure 2].


The results for shimmer indicate that in the females, in the early and late chronotypes, it was high in the evening, whereas in the mid (P = 0.04) chronotypes, it was high in the night. On the contrary, in the males, the shimmer was observed to be high in mid (P = 0.03) and late (P = 0.05) chronotypes at night, whereas in the early chronotypes, it was high in the morning [Figure 3].


According to various studies, CRs cause the loss of productivity, health risks such as increased propensity for cancer, depression, sleep disturbances, gastrointestinal disorders, metabolic and cardiovascular disorders, decreased immune response and life span, glucose intolerance, diabetes, and hypertension.[13] From a health perspective, the human voice has been shown to reflect the general health and well-being of an individual. A person's voice indicates who he/she is and how he/she feels and giving considerable insights into the structure and function of certain parts of the body.[14] The aim of the current study was to understand the role of CR on human voice in young adults by analyzing the three important and commonly analyzed parameters of voice such as fundamental frequency (F0), jitter and shimmer across four time points a day.

In this study, we observed that the voice parameters changed with the time of the day and that CR had a role to play [Figure 1], [Figure 2], [Figure 3]. To ascertain this, we recorded the voice at four time points in healthy young adults who were not voice professionals and stratified the data considering their chronotype and gender. The sample size studied was reasonably big (98 males and 118 females), and voice was recorded on the same day for each volunteer in a voice laboratory. As far as the authors are aware of, there are no studies which address the impact of CR on voice. The only report that sheds light in this aspect is the seminal study of Artkoski et al.,[15] who studied the changes in vocal parameters of teachers (11 females and 10 males [mean ages 30 and 40 years]). The investigators analyzed the vocal parameters in the forenoon and in the afternoon with an interval of 6–8 h and reported that the in most volunteers F0 was higher in the afternoon; although, the change was on the average small (in most cases within 5 Hz) and statistically nonsignificant.[15] They also observed that the alpha ratio was significantly higher for the females and lower for the males in the afternoon and that the gender difference in the vocal changes was important.[15] However, the authors had not documented the chronotype of the volunteers.

In this study, it was also observed that the pitch in females was elevated in the late chronotypes in the evening, whereas it was high in the early and mid in the morning. However, in males, the pitch was observed to be high in the early chronotypes at night and almost equal at both morning and night in the mid chronotypes. The most important observation was that in the late chronotypes when compared to the morning time point, the pitch was high at midday, evening, and night. Previous studies with 20 vocally healthy untrained women between the ages of 18 and 35 years have shown that there was no evidence as to how time-of-day affects the voice range profile performance.[16] Reports also suggest that the mean fundamental frequency (F0) was higher in the evenings than in the morning without any vocal loading.[17]

The results of the current study indicate that the CR has got a very strong relationship with human voice and it was observed that the voice quality varies across the evening type, intermediate type, and morning type and that these were significant across gender also. A person who is known to be a morning type will have a good voice quality at early morning and his voice quality decreases as the day progresses toward the night time. On the contrary, the results also suggest that in the intermediate group, there is no significant change in the voice quality across the day and it will be the same throughout the day. However, the most vital observation is that in the evening type people, the voice quality will be good at evening and the quality will be very poor in the early morning.


The findings of this study are very important, especially for the professional voice users as they can select their time slot for the performance or speech according to their circadian pattern. This will help them in their professional endeavors and may mitigate the chances of developing any voice problems.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.


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