Table 2. Acoustic characteristics in the different phases of the menstrual cycle with results of statistical tests.

		Cycle Phase
Acoustic Variable	Follicular	Pre-Ovul	Ovulatory	Luteal	Menstr.	F	P	Partial Eta2	Observed Power
Fundamental frequency	213±3	212±3	211±3	214±3	214±4	0.90	0.464	0.011	0.285
F0 maximum	252±4	251±4	249±5	254±4	256±5	1.63	0.165	0.020	0.502
F0 minimum	185±3	185±3	185±3	187±3	185±3	0.35	0.840	0.005	0.131
F0 SD	5.3±0.3	5.4±0.3	5.0±0.2	5.5±0.3	5.6±0.4	1.32	0.262	0.017	0.412
Degree of unvoiceness	8.2±0.9	8.0±0.9	7.2±0.6	7.1±0.8	9.1±1.1	2.89	0.022	0.036	0.779
Noise-to-harmonic ratio	0.139±0.004	0.138±0.004	0.132±0.003	0.141±0.005	0.147±0.007	2.50	0.042	0.031	0.710
Shimmer	4.3±0.3	4.6±0.3	4.2±0.2	4.3±0.3	4.5±0.3	0.86	0.487	0.011	0.274
Jitter	2.1±0.1	2.1±0.2	1.9±0.1	2.0±0.1	2.1±0.2	1.85	0.119	0.023	0.559

Mean and s.e.m for N = 23 women and results of the statistical analysis the effect of cycle phase on different acoustic variables.

GLM with subject and vowel as random factor, and menstrual cycle phase as fixed factor; df = 4,313 for all analyses. Partial Eta² provides an overestimate of the actual effect size; observed power gives the probability that the test statistic is greater than the critical value under the alternative hypothesis.