Not much is known about acoustic cues concerning consonant place and voicing of whispered fricatives, so the productions of sustained sibilants, disyllabic words, sentences and reading of a phonetically balanced text, were compared in voiced and whispered speech modes. Spectral peak frequencies and levels, spectral slopes, sound pressure level and durations were calculated. A Functional Principal Component Analysis (FPCA) of Power Spectral Density (PSD) estimates of voiced, whispered, and whistled fricatives was developed. The broad peak frequency was used to discriminate /s/ and /ʃ/. Spectral slope and broad peak frequency were associated with place. FPCA scores revealed various sources of variation. PSD was significantly different in voiced, whispered, and whistled fricatives. The relative duration of same-place voiceless fricatives was higher than voiced fricatives both in voiced and whispered speech. This evidence can be used to restore voiced speech signals from aphonic patients.