ACOUSTIC ANALYSIS OF VOWEL EMISSION IN OBSTRUCTIVE SLEEP-APNEA

We studied vocalization in 18 men with obstructive sleep apnea syndrom e (OSAS) (age, 49 [7.5] years; body mass index [BMI] 33.6 [7.6]) and 1 0 normal men as a control group (age, 46.7 [6.2] years; BMI 24.6 [2.2] ). Polysomnographic data for patients with OSAS were as follows: total sleep time (TST), 387.5 [27.9] min; awake, 17.6 (12.6% TST); stage 1, 19.8 (18.7 percent TST); stage 2, 54.8 (23.2 percent TST); stage 3 an d 4, 1.5 (0.3 percent TST); and stage REM, 4.2 (1.7 percent TST). Apne a hypopnea index (AHI) was 43.0 (18.2) and lowest O2 saturation was 73 .6 (11.4). We recorded the following sounds in all subjects: /a/ as in ''father''; /e/ as in ''get''; /i/ as in ''see''; /o/ as in ''go''; / u/ as in ''too.'' Three maneuvers for each vowel sound were taken for analysis. Signals were digitized at 10,000 Hz. Fast Fourier transform ation was applied to segments of 512 points of each utterance correspo nding to the vowel sound. The following parameters were obtained: maxi mum frequency of harmonics, mean frequency of harmonics, and the numbe r of harmonics. Results: There were significant differences between bo th groups in the maximum frequency of harmonics of /i/ and /e/ vowels. (For /i/: 2,650 [672] Hz controls; 425 [71.2] Hz OSAS. For /e/: 2,605 [772.3] Hz controls; 1,250.0 [828.41 OSAS.) The number of harmonics f or /i/ vowel was 4.5 (1.2) for controls as compared with 2.7 (1) Hz fo r OSAS. Conclusions: Vocalization in patients with OSAS is different f rom normal subjects. Vowel /i/ can distinguish these patients from nor mal subjects.