Abstract
Rapidly evolving global economic status has changed professional behavior. Of late, there is a drastic increase in professional voice users and thereby increase in the patients with voice disorders. Clinically, the changes in the voice can only be perceived but cannot be quantified and documented. It is therefore necessary to have a gadget/tool which is simple and with which we can document and quantify the voice change objectively. This is a prospective case control study with 50 normal control subjects (25 male and 25 female subjects) who had no voice complaints and 50 patients(cases) who presented with complaints of change in voice due to various voice pathologies, the voices were recorded from the control group and also from the cases group both pre and posttreatment and were analyzed. The disease specific frequency in various pathologies of voice pre and post treatment were documented. The degree of change in voice frequency pre and post treatment were compared with each other and with the average frequency obtained from the voices in the control group. Office based acoustic analysis can definitely be used as a simple tool for documenting voice changes on outpatient basis and it provides a dependable documented evidence with which we can even compare the results following treatment.
Keywords: Professional voice users, Voice analysis, Acoustic analysis, Fundamental frequency, PRAAT software
Introduction
Each person has a distinct voice that distinguishes one speaker from the other. The characteristic voice is a product of the organic and phonetic features of the speaker and is unique for each individual. Voice is the sound produced by humans and other vertebrates using the lungs and the vocal folds in the larynx. It forms an integral part of the unique human ability to communicate by speech. Normal voice is defined as one which has the following characteristics-
It is audible, clear or stable in a wide range of acoustic settings
It is appropriate for the gender and age of the speaker
It is capable of fulfilling its linguistic and paralinguistic functions
It does not fatigue easily
It is not associated with discomfort and pain on phonation.
Pitch is the most important characteristic of the voice and is the perceptual attribute of voice frequency, which is primarily determined by the number of vibrations per second produced by the mucosal cover over the vocal cords within the larynx. Any alteration in the factors such as mass or length of the vocal cord, tension within the vocal cord, compliance of the mucosal cover, and subglottic pressure affect the pitch. They cause varying degrees of disturbance to vocal fold vibrations or glottic closure, rendering the voice hoarse.
Professional voice users are persons who use their voice as a primary means of occupational communication. It includes the working population such as singers, actors, teachers, lawyers, politicians, salespersons, public speakers, telephone operators, etc. Among them, performing vocal professionals such as singers and actors have the highest demand on the vocal apparatus and push their voices to the limits. These professionals are sensitive to even subtle changes in their voices. Recent trends, change in lifestyles, and ever-increasing professional demands for voice are leading to increased incidence of voice disorders.
Otolaryngologists being the primary consultants for the voice problems, have to work in an ever demanding society. We need a tool with which we can document the changes in the voice. The tool must be simple and easy to utilise without much restrain. It should be able to record the voice of the patient pre-treatment and post treatment and at the same time should be able to analyse the changes in the parameters of voice and document them. In this study we used a simple free software with which we have recorded the pre and post treatment voices of the patients who presented with voice disorders and analysed them to document the changes in the voice parameters (Table 1–3).
Table 2.
Voice analysis in male patients with various pathologies pre and post treatment
| Disease condition | No of patients | Pre treatment f0 | Post treatment f0 | Change |
|---|---|---|---|---|
| Vocal nodules | 3 | 119.49 ± 2.78 | 138.05 ± 4.94 | 18.56 |
| Vocal polyp (sessile) | – | – | – | |
| Vocal polyp (pedunculated) | 3 | 131.36 ± 2.98 | 139.57 ± 3.17 | 8.21 |
| Rinkes edema | 3 | 100.42 ± 1.82 | 128.12 ± 3.63 | 27.7 |
| Laryngitis acute | 4 | 113.46 ± 5.21 | 138.79 ± 2.89 | 25.33 |
| Laryngitis chronic | 3 | 101.5 ± 3.08 | 105.57 ± 4 | 4.05 |
| Vocal cyst | 4 | 108.75 ± 2.87 | 137.91 ± 2.35 | 29.16 |
| papilloma | 2 | 94.25 ± .54 | 94.38 ± 0.5 | 0.13 |
| puberophonia | 3 | 218.56 ± 25.39 | 129.18 ± 20.07 | 89.38 |
Table 1.
Mean Fundamental frequency of voice (f0) males and females in control group
| Fundamental frequency | Male | Female |
|---|---|---|
| CONTROLS | 140.27 ± 6.58 | 231.78 ± 8.33 |
Table 3.
Voice analysis in female patients with various pathologies pre and post treatment
| Disease condition | No of patients | Pre treatment f0 | Post treatment f0 | Change |
|---|---|---|---|---|
| Vocal nodules | 7 | 208.01 ± 5.1 | 227.3 ± 7.58 | 19.27 |
| Polyps sessile | 3 | 205.64 ± 5.76 | 230.48 | 23.14 |
| Polyps peduculated | 2 | 225.7 | 228.34 | 4.76 |
| Rinkes edema | 1 | 190.13 | 223.68 | 33.5 |
| Cyst | 4 | 196.9 ± 8.26 | 227.48 ± 3.20 | 30.56 |
| Papilloma | – | |||
| Androphonia | 1 | 170.61 | 209.15 | 38.54 |
| Laryngitis acute | 5 | 205.9 ± 1.39 | 227.97 ± 2.57 | 22.06 |
| Laryngitis chronic | 2 | 194.54 | 205.39 | 10.85 |
Patients and Methods
This study was a prospective Case–control study undertaken through a period of 24 months from September 2017 to September 2019 in tertiary care hospital. The study included 50 normal control subjects (25 male and 25 female subjects) who had no voice complaints and 50 patients(cases) who presented with complaints of hoarseness of voice. The control group were evaluated by performing voice analysis after taking informed consent from them. The cases group was evaluated by obtaining a brief history, performing a diagnostic video laryngoscopy, and an objective voice evaluation after taking informed consent from the patient. The patients were treated with appropriate medical/surgical methods based on the pathology identified. The patients were reviewed one month postoperatively, and video laryngoscopy and voice evaluation were performed on review. The results of voice fundamental frequency pre and post treatment were compared with each other and with the average frequency in control males and females.
Voice analysis was performed on PRAAT software. Each patient underwent voice analysis with voice recorded in a quiet room using a commercial microphone held at 15 cms from the patient. Patients were asked to phonate continuously with a spontaneous speech at their comfortable level for 60–90 s. To avoid acoustic.
variability due to initiation and termination, only the mid-portion of each voice with good quality continuous signal was selected (15 – 20 s) and analyzed on a personal computer. PRAAT is an open-source, free software created by Paul Boersma and David Weenik at the Institute of Phonetics Sciences, University of Amsterdam, for scientific analysis of the sound signals recorded. The fundamental frequency of voice was assessed on acoustic analysis.
Treatment of vocal cord lesions:
After undergoing all pretreatment procedures, patients were subjected to surgical or medical therapy according to the diagnosis after obtaining consent. For vocal cord nodule, polyp, cyst, Reinke's edema, laryngeal papillomatosis, micro laryngeal excision surgery was performed. For puberphonia, type III thyroplasty was done. For androphonia, type IV thyroplasty was done. Patients with acute and chronic laryngitis were treated with appropriate medical management. Patients were advised regarding the effective use of voice and dietary habits and were asked to review after one month.
Results
The study comprised 50 patients who presented with complaints of hoarseness of voice and 50 control subjects with normal voice.
Age
The control group comprised of 50 subjects who are in the age group ranging between 18 -68 years. The cases group comprised 50 patients who are in the age group range of 18–68 years.
Since the basic fundamental frequency in males and females is different, male and female patients were studied separately.
Among the above clinical conditions, papilloma showed least post treatment improvement in terms of frequency followed by chronic laryngitis. Pedunculated polyps didnot show much variation in terms of frequency.
Results shows there is significant difference in the pre-treatment frequency and post treatment frequency values in most of the conditions except few like papillomatosis and chronic laryngitis. Even the difference in pre treatment values with fundamental frequency for that age and sex can also be documented (Table 4–7).
Table 5.
Comparison of voice frequency pre and post treatment with fundamental frequency in males
| Disease | Fundamental frequency (Cf0) | Pre treatment f0 | Post treatment f0 |
|---|---|---|---|
| Vocal nodules | 140.27 ± 6.58 | 119.49 ± 2.78 | 138.05 ± 4.94 |
| Vocal polyp (sessile) | 140.27 ± 6.58 | – | – |
| Vocal polyp (pedunculated) | 140.27 ± 6.58 | 131.36 ± 2.98 | 139.57 ± 3.17 |
| Rinkes edema | 140.27 ± 6.58 | 100.42 ± 1.82 | 128.12 ± 3.63 |
| Laryngitis acute | 140.27 ± 6.58 | 113.46 ± 5.21 | 138.78 ± 2.89 |
| Laryngitis chronic | 140.27 ± 6.58 | 101.5 ± 3.08 | 105.57 ± 4 |
| Vocal cyst | 140.27 ± 6.58 | 108.75 ± 2.87 | 137.91 ± 2.35 |
| Papilloma | 140.27 ± 6.58 | 94.25 ± .54 | 94.38 ± 0.5 |
| Puberophonia | 140.27 ± 6.58 | 218.56 ± 25.39 | 129.18 ± 20.07 |
Table 6.
Mean change in pre and post treatment in males
| Males | Fundamental (Cf0) | Pre treatment f0 | Post treatment f0 | p value |
|---|---|---|---|---|
| 25 | 140.27 ± 6.58 | 106.53 | 127.46 | < 0.0001 |
| Range | 127–149 | 93.86–133.48 | 94.34–141.82 |
Table 4.
Comparison of voice frequency pre and post treatment with fundamental frequency in females
| Disease | Fundamental frequency (Cf0) | pre-treatment f0 | Posttreatment f0 |
|---|---|---|---|
| Vocal nodules | 231.78 ± 8.33 | 208.01 | 227.3 |
| Polyps sessile | 231.78 ± 8.33 | 205.64 | 230.48 |
| Polyps peduculated | 231.78 ± 8.33 | 225.7 | 228.34 |
| Rinkes edema | 231.78 ± 8.33 | 190.13 | 223.68 |
| Cyst | 231.78 ± 8.33 | 196.9 | 227.48 |
| Androphonia | 231.78 ± 8.33 | 170.61 | 209.15 |
| Laryngitis acute | 231.78 ± 8.33 | 205.9 ± 1.39 | 227.97 |
| Laryngitis chronic | 231.78 ± 8.33 | 194.54 | 205.39 |
Table 7.
Mean change in pre and post treatment in females
| Females | Fundamental (Cf0) | Pre treatment f0 | Post treatment f0 | p value |
|---|---|---|---|---|
| 25 | 231.78 | 204.98 | 226.67 | < 0.0001 |
| Range | 220–251 | 185.73–225 | 205–242 |
Discussion
Humans express ideas, thoughts, and feelings orally to one another through a series of complex words that are articulated by articulators by molding the basic sound produced from the vocal cords into specific decodable sounds called speech.
Voice production requires-
Actuator (generator)-lungs and diaphragm
Vibrator(transducer)-that converts aerodynamic energy into acoustic energy.
Resonators
Articulators
A neurologically competent larynx which can adduct the cords with adequate length and tension, covered by a healthy and regular mucosa that can vibrate freely, acts as a transducer.
The vibrating mucosa over the vocal cords produces the raw glottal sound. This fundamental vibratory sound is modified and resonated by the supraglottal vocal tract to produce the characteristic individualized voice quality. The articulatory structures shape the sound into an infinite number of combinations of words to make speech. The quality of the sound produced depends upon the vibratory characteristics of the mucosal wave over the vocal cord.
The basic perceptual characteristics of the voice are pitch, intensity, quality, duration.
Pitch is the character that varies from person to person and defines the quality of the voice in each individual.
Pitch is measured in terms of frequency, which is the number of vibrations produced by the mucosal wave per second. It is determined by the compliance of the mucosal cover, intactness of the Reinke’s space, tension within the vocal cord, and subglottic pressure.[1]
Alterations in the thickness, mass of the vocal cord, the composition of the Reinke’s space, the tension in the underlying structures (vocalis muscle), and resistance to subglottic pressure directly affects the pitch by varying the number of vibrations per second. The human voice is a combination of periodic and aperiodic sound. The irregular waveform of vibration of the vocal cord will result in aperiodic sound that is perceived as hoarseness [2].
Frequency of voice can be altered by any lesions which affect-
Part of the mucosa covering the vocal cord
The entire length of the mucosa of the vocal cord
Cross-section of the vocal cord (superficial, intermediate and deep layers of lamina propria, vocalis muscle)
Length or tension within the vocal cord.
Movement of the vocal cord.
Benign vocal cord lesions comprise about 50% of the patients presenting with. hoarseness of voice [3].
The overall mean f0 of voice in male patients with pathological conditions (except Puberophonia) was 109.89 Hz, which was 30.38 Hz lower compared to the male Cf0 of 140.27 Hz. This change in the f0 was established by a statistically significant p value of < 0.001. The overall mean f0 post treatment in males was 126.05 Hz which showed an improvement of 16.16 Hz as compared to mean pre-treatment f0 (excluding puberophonia) of 109.89 Hz and this improvement was established with a statistically significant p value of < 0.0001.
The overall mean f0 in females with pathological conditions (except Androphonia) was 204.98 Hz, which was 26.8 Hz lower compared to the female Cf0 of 231.78 Hz. This change in the f0 compared to mean normal f0was established with a statistically significant p value < 0.0001. The overall mean f0 post treatment in females was 226.67 Hz, which showed an improvement of 21.69 Hz from the pre-treatment f0 (excluding androphonia) of 204.98 Hz. This change was established with a statistically significant p value < 0.0001.
Overall, the voice analysis showed a significant reduction in frequency in both males and females with pathologies of the cords compared to the mean Cf0. A similar reduction in the frequency was observed in the studies by Ali Dehqan et al. [4] and Torabinenzhad F et al. [5] in laryngeal pathologies. The improvement in the frequency of voice posttreatment was also significant and was supported with a statistical significance p value < 0.0001. The improvement was corresponding with the studies by Petrovic-Lazic et al. do Amaral Catani et al., Chhetri et al., Nitish Virmani et al. [6–9] Hoarseness of voice can be objectively measured by voice analysis. The degree of hoarseness of voice can be measured and documented in terms of change in the f0.
The extent of change is directly related to the extent of involvement of the mucosa of the cord and the underlying structures. Pathologies involving a part of the mucosa like vocal nodules, cysts, pedunculated polyps showed about 10–30 Hz change in f0, and those involving the entire length of the mucosa as in acute and chronic laryngitis showed a reduction of 30–40 Hz change. Conditions involving deeper structures like reinke’s edema and papillomatosis showed a reduction of 35- 45 Hz change in f0. Puberphonia showed an average of 78.29 Hz higher f0 than Cf0. Androphonia showed a reduction of 61.17 compared to female Cf0. Pathologies that were involving the deeper structures of the lamina propria and vocalis muscles showed significantly lowered frequency values. The lowest change was noted in pedunculated polyps of 8.91 Hz in males, and 6.06 Hz in females and the highest change was noted in laryngeal papillomatosis of 46.02 Hz in males and Reinke’s edema of 41.64 Hz in females. Puberphonia showed a f0, which was 78.29 Hz higher than the control males f0 and Androphonia of 61.17 Hz lower than female Cf0.
A significant change in the voice frequency was noted post treatment in pathologies such as acute laryngitis, vocal nodules, vocal cysts, vocal polyps, Puberphonia, and Androphonia. However, in chronic laryngitis and laryngeal papillomatosis conditions, the f0 did not show a significant improvement, and the post-treatment f0 values were still lower compared to the f0 in controls. Acoustic Voice analysis helps us in guarded counselling of the patients depending on underlying condition. It does have a role in evaluating a patient with hoarseness of Voice [10] along with the current gold standard visualization techniques. Acoustic voice analysis can be used to objectively document the degree of hoarseness of voice by the change in the f0 [11] and also in documenting the outcome of treatment.[ [12–19].
Conclusion
Office based acoustic analysis can be used as an adjunctive tool in effectively documenting the professional voice disorders. It can document the diagnosis of functional voice disorders like Puberophonia and Androphonia by measuring the deviation in the fundamental frequency. The effectiveness of treatment can also be assessed with acoustic analysis. The improvement in voice frequency can thus be objectively documented. The acoustic analysis provides an objective, documentable, and measurable data of vocal function. These measurements are clinically helpful for the comparison of the patient's voice with those of healthy speakers and in assessing the functional outcome of voice post-treatment when pathological lesions of the vocal folds were removed, and conditions of normal phonation were restored thereby providing an accurate and documentable evidence of the effectiveness of treatment.
Abbreviations
- F0/f0
Fundamental frequency of the voice
- Cf0
Frequency of voice in controls
- Hz
Hertz
Funding
No funding was utilised for the study.
Declarations
Conflict of interest
No potential conflict of interests.
Footnotes
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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