Voice Analysis in Post Tonsillectomy Patients

Abstract

The main aim of this study was to analyse the change in voice in terms of acoustic parameters and its perceptual impact in patients who have undergone tonsillectomy. A prospective study was conducted in our institution—JSS Hospital and JSS institute of speech and hearing, Mysore for a duration of 1 year (December 2015–December 2016). 50 post tonsillectomy cases were selected randomly and subjected to acoustic analysis. It was inferred that situation of vocal analysis and assessment for the vowels ‘a’, ‘i’ and ‘u’ under the categories hoarse, harsh and breathy remain more or less the same during preoperative stages, first preoperative follow up and the second post operative follow up. It was concluded that tonsillectomy did not appear to change the acoustic features of vowels remarkably. It was assumed that the subject may adjust the shape of the vocal tract to produce consistent speech sound after surgery using auditory feedback.

Introduction

Tonsillectomy is performed because of infectious factors such as recurrent acute tonsillitis, chronic tonsillitis, and peritonsillar abscess, as well as airway obstruction related to hypertrophy of the tonsils, asymmetrical tonsillar hypertrophy, and tumors of the tonsils [1]. Tonsillectomy (excision of palatine tonsils) is a surgery executed on modulation of structures of the vocal tract [2].

The voice is basically a product of three physiological processes: a constant expiratory airflow controlled by chest muscles; production of glottal sound through vibration of the vocal folds, and a change in this sound with amplification and muffling of sound frequencies resulting from the action of pharyngeal, oral and nasal resonant structures (vocal tract) [3]. Activator, vibratory, resonator, and articular organs must act in harmony with the central nervous system for the production of voice and speech. Voice is mainly produced in the larynx and gains its acoustic characteristics in the vocal tract. Oral cavity, lips, soft palate, and tongue are quite important for resonance and articulation [4]. Palatine tonsils, which are components of the oral cavity, affect voice and speech. This effect is supposed to appear in two ways. In the first one, it was suggested that palatine tonsils affect the quality of the resonance in the vocal tract by a mass effect. Secondly, palatine tonsils may affect nasal resonance together with articulation owing to their natural tissue characteristics [5].

It could be supposed that tonsillectomy would affect voice because of localization and characteristics of the palatine tonsils. The trauma and edema due to the usage of a mouth gag during tonsillectomy, the trauma and edema of the surgical procedure in the oropharynx, healing tissue and scar in the area of tonsillectomy, and widening of the airway after removal of the palatine tonsils were supposed to affect voice [1]. Enlarged tonsils decrease oropharyngeal airspace, push the tongue forward and cause hypernasal speech, oral breathing and a muffled voice; for this reason the effects of tonsillectomy may also influence consonants, while several studies report data only on the fundamental frequency and the first two to four formant frequencies of the vowels [6].

Potential deterioration of the voice quality may be of great importance for some patients (e.g. performing actors or singers) and it may significantly affect their eventual decision to undergo the surgery. Therefore it seems purposeful to determine objectively the changes in voice quality resulting from tonsillectomy treatment [2].

Presently acoustic analysis of voice is one of the most attractive methods of assessing the phonatory functions providing the quantitative and qualitative data [7]. In this study, the effects of tonsillectomy on the voice assessment are analysed.

Materials and Methods

Patients and clinical materials available at JSS Hospital and JSS Institute of Speech and Hearing were taken for the study during the study period. Data was collected in a pretested proforma meeting the objective of the study. 50 cases were selected from the total number of cases by using the simple random sampling method. The analysis was done by using the parameters—the mean, the standard deviation, standard error, t test and Chi square test.

Patients with chronic tonsillitis and above the age of 5 years were included in the study. Patients below the age of 5 years, patients who have changes of voice during puberty, those who have anatomical defects of nose and palate and those who have chronic tonsillitis associated with laryngeal, nasal and ear pathology were excluded out of the study.

In order to estimate the change in acoustic parameters, subjects were required to sustain the vowels/a/,/i/,/u/and read in conversational pitch and loudness and their voices were recorded pre and post tonsillectomy using a computer. Post-operative recordings were repeated twice until 4th post operative week. To extract the acoustic parameters, the acoustic analysis system Dr Speech Software Version 4 was used.

Results

It was observed from the study that the maximum cases were in the age group of 5–11 years among males constituting 38.9%. Among females the maximum cases were in the age group of 5–11 years and 26+ , each accounting for 28.1%. Both sexes put together, the maximum cases were in the age group of 5–11 years accounting for 32%.

From the below study it has been found that the difference between the means of males and males is not statistically significant.

In the below study it is observed that;

1. For vowel/a/

   1. The difference in the mean between S₀ and S₁ was statistically not significant.
   2. The difference in the mean between S₀ and S₂ was statistically significant.
   3. The difference in the mean between S₁ and S₂ was statistically significant.
2. For vowel/i/

   1. The difference in the mean between S₀ and S₁ was statistically not significant.
   2. The difference in the mean between S₀ and S₂ was statistically significant.
   3. The difference in the mean between S₁ and S₂ was statistically not significant.
3. For vowel/u/

   1. The difference in the mean between S₀ and S₁ was statistically significant.
   2. The difference in the mean between S₀ and S₂ was statistically not significant.
   3. The difference in the mean between S₁ and S₂ was statistically significant.

According to the study which we have conducted the following inference has been derived regarding,

1. For vowel/a/

   1. Hoarse—the difference in the mean value between one stage to the other stage was not statistically significant.
   2. Harsh—the difference in the mean value between one stage to the other was not statistically significant.
   3. Breathy—the difference in the mean value between one stage to the other was not statistically significant.
2. For vowel/i/

   1. Hoarse—the difference in the mean value between one stage to the other stage was not statistically significant.
   2. Harsh—the difference in the mean value between one stage to the other was not statistically significant.
   3. Breathy—the difference in the mean value between one stage to the other was not statistically significant.
3. For vowel/u/

   1. Hoarse—the difference in the mean value between one stage to the other stage was not statistically significant.
   2. Harsh—the difference in the mean value between one stage to the other was not statistically significant.
   3. Breathy—the difference in the mean value between one stage to the other was not statistically significant.

Discussion

The effects of tonsillectomy over voice have not been studied extensively from the perspective of acoustic changes, other than its effect on nasalance. A few studies have examined potential changes in vocal quality after tonsillectomy. In general, minimal changes were found [8]. Tonsillectomy can affect the voice by enlarging the resonating chamber and altering the formant frequencies or by altering the conformation of the tonsillar fossae. Potentially, part of the soft palate musculature can be removed or disturbed. This could theoretically lead to scarring and subsequent limitation of fine motor control or even velopharyngeal closure [9].

Formants are the resonant frequencies of the vocal tract when vowels are pronounced. While vowels are attributed to this periodic resonance, consonants are not periodic. They are produced by restriction of air flow with the mouth, tongue, and jaw [10]. Formant refers to peaks in the harmonic spectrum of a complex sound which arise from some sort of resonance of the source. Because of their resonant origin, they tend to stay essentially the same when the frequency of the fundamental is changed [11]. A formant is a frequency range in which a phenome has its most distinctive and characteristic pitch. Although all phenomes have their own formants, vowel sound formants are usually the easiest to identify. Almost all formants have the trait of waxing and waning in energy in all frequencies, which is caused by the repeated closing and opening of the human vocal tract. On average, this repeated closing and opening occurs at a rate of 125 times per second in an adult male and 250 times per second in an adult female. This rate gives the sensation of pitch (higher frequencies result in higher pitches) [12].

Sundberg has identified portions of the vocal anatomy which he associates with the formant frequencies. The jaw opening, which constricts the vocal tract toward the glottal end and expands it toward the lip end, is the deciding factor for the first formant. This formant frequency rises as the jaw is opened wider. The second formant is most sensitive to the shape of the body of the tongue, and the third formant is most sensitive to the tip of the tongue [11].

It is not expected that fundamental frequency (F0) change after tonsillectomy. Because it is an operation that did not directly affect larynx and not influence the rate at which vocal folds open and close during phonation [12].

Chuma et al. reported that tonsillectomy had only minor quantitative and qualitative effects on various acoustic parameters. Saida et al. and Hori et al. also reported similar observations in their Studies [12]. In a retrospective study among the performing artists done by Jarboe et al. it was stated that patients voices were not impaired after tonsillectomy [9].

Patients may ask about the possibility of voice changes after tonsillectomy. Patients perception of voice is an important treatment outcome measure, especially in the case of benign disease where the greatest impact is on the quality of life. They should be advised of potential voice changes, especially professional voice users who may be particularly sensitive to changes in resonant characteristics. However, according to Behrman et al. one-fifth of the patients perceived their voices to be improved after surgery and none thought that the voice to be worse [13]. Therefore, it is concluded that patients are unlikely to perceive a change in voice as a result of surgery, but in those cases where a difference is perceived, it is likely to be a positive change.

Conclusion

From the present study it can be inferred that the situation of vocal analysis and assessment of the vowels/a/,/i/and/u/under the categories hoarse, harsh and breathy remain more or less same during the preoperative changes, first and second post operative follow up. It was determined that tonsillectomy did not appear to change the acoustic features of vowels remarkably, it was assumed that subject may adjust the shape of vocal tract to produce consistent speech after surgery using auditory feedback.