To analyze voice function before and after thyroidectomy for patients with normal preoperative voice using a standardized multidimensional voice assessment protocol. The natural history of post-thyroidectomy voice disturbances for patients with preserved laryngeal nerve function has not been systematically studied and characterized with the intent of using the data for postoperative voice rehabilitation. During a prospective single-arm study, patients with normal voice underwent functional voice testing using a standardized voice grading scale and a battery of acoustic, aerodynamic, glottographic, and videostroboscopic tests before, 1 week after, and 3 months after thyroidectomy. Differences in observed sample means were evaluated using analysis of covariance or t test; categorical data was analyzed using the Fisher exact or chi-square test. Fifty-four patients were enrolled; 50 and 46 were evaluable at 1 week and 3 months, respectively. No patient developed recurrent laryngeal nerve injury; one had superior laryngeal nerve injury. Fifteen (30%) patients reported early subjective voice change and seven (14%) reported late (3-month) subjective voice change. Forty-two (84%) patients had significant objective change in at least one voice parameter. Six (12%) had significant alterations in more than three voice measures, of which four (67%) were symptomatic, whereas 25% with three or fewer objective changes had symptoms. Patients with persistent voice change at 3 months had an increased likelihood of multiple (more than three) early objective changes (43% vs. 7%). Early maximum phonational frequency range and vocal jitter changes from baseline were significantly associated with voice symptoms at 3 months. Early vocal symptoms are common following thyroidectomy and persist in 14% of patients. Multiple (more than three) objective voice changes correlate with early and late postoperative symptoms. Alterations in maximum phonational frequency range and vocal jitter predict late perceived vocal changes. Factors other than laryngeal nerve injury appear to alter post-thyroidectomy voice. The variability of patient symptoms underscores the importance of understanding the physiology of dysphonia.

Electroglottographic (EGG) and acoustic records from 10 normal men prolonging the vowel /a/ at 60–68 dB, 70–78 dB, and 80–88 dB SPL were obtained. "Contact quotient" (EGG duty cycle) was shown to vary directly with vocal SPL. The mean contact quotient was 0.57 (SD=0.07) and varied on the order of 1% over the course of a given phonation. "Contact index," a metric of EGG symmetry, also tended to vary with SPL. Consistent with previous qualitative descriptions of EGG morphology in modal register voice, the contact ndex averaged –0.52 (SD=0.08), indicating that the EGG "closing phase" represents about 24% of the entire "contact phase" Contact index was more variable than contact quotient on consecutive EGG waves, varying by about 10% during phonation. Subjects were also instructed to produce a slow crescendo. Sound pressure and EGG data indicated that both the slope of Increasing EGG contact and EGG duty cycle were significantly related to the amplitude of the acoustic signal These results suggest that quantitative electroglottography may provide powerful insights nto the control and regulation of normal phonation and into the detection and characterization of pathology.

One-second acoustic samples were extracted from the mid-portion of sustained /a/ vowels produced by 50 black and 50 white adult males. Each vowel sample from a black subject was randomly paired with a sample from a white subject. From the tape-recorded samples alone, both expert and naive listeners could determine the race of the speaker with 60% accuracy. The accuracy of race identification was independent of the listener’s own race, sex, or listening experience. An acoustic analysis of the samples revealed that, although within ranges reported by previous studies of normal voices, the black speakers had greater frequency perturbation, significantly greater amplitude perturbation, and a significantly lower harmonics-to-noise ratio than did the white speakers. The listeners were most successful in distinguishing voice pairs when the differences in vocal perturbation and additive noise were greatest and were least successful when such differences were minimal or absent. Because there were no significant differences in the mean fundamental frequency or formant structure of the voice samples, it is likely that the listeners relied on differences in spectral noise to discriminate the black and white speakers.

Signal-averaging and autocorrelation analysis revealed that the cardiovascular system exerts a modest but consistent influence on vocal fundamental frequency (F ₀ ), accounting for approximately 0.5% to 20% of the absolute F ₀ perturbation (jitter) measured during a sustained phonation. There was also a marked trend for this percentage to decrease with increasing vocal F ₀ . Estimated mean "deterministic jitter" (J ) values of 3.7 µsec (SD = 3.2) and 0.9 µsec (SD = 0.5) were derived from 6 normal male and 6 normal female subjects, respectively, with an overall mean of 2.3 µsec (SD =2.7). These values represent approximately 6.9% of the mean total jitter for men and 2.4% of the mean total jitter for women, or about 4.6% for all subjects. The results are discussed in terms of their significance regarding more reliable vocal jitter measurement.