Table 1.
Normative values of formant frequencies in male groups of iRBD, PD and HC.
| iRBD | PD | HC | |
|---|---|---|---|
| mean/SD (range) | mean/SD (range) | mean/SD (range) | |
| F1/a/ (Hz) | 548/43 (448−627) | 548/53 (452−676) | 582/49 (497−667) |
| F2/a/ (Hz) | 1331/78 (448−627) | 1328/81 (1172−1567) | 1350/86 (1119−1535) |
| F1/i/ (Hz) | 331/16 (300−376) | 332/18 (293−380) | 348/23 (304−408) |
| F2/i/ (Hz) | 1980/108 (1680−2179) | 1931/128 (1703−2190) | 2012/103 (1750−2226) |
| F1/u/ (Hz) | 331/19 (294−377) | 337/20 (295/401) | 340/20 (299−405) |
| F2/u/ (Hz) | 770/64 (661−957) | 786/52 (680−894) | 762.9/54 (666−903) |
iRBD, isolated rapid eye movement sleep behaviour disorder, PD Parkinson’s disease, HC Healthy control, F1 First formant frequency, F2 Second formant frequency