adj.spoken in soft hushed tones without vibrations of the vocal cords

"a long whispered conversation"

Acoustic Analysis of Consonants in Whispered Speech
Acoustic analysis and recognition of whispered speech
Speaker Identification Within Whispered Speech Audio Streams
Acoustic Analysis and Recognition of Whispered Speech
Identification of speaker sex from isolated, whispered vowels.
Identifiability of vowels and speakers from whispered syllables
Formant Feature Differences Between Whispered And Voiced Sustained Vowels
Formant feature differences between whispered and voiced sustained vowels
Analysis and classification of speech mode: Whispered through shouted
Speaker sex identification from voiced, whispered, and filtered isolated vowels