most studies on whispering deal with its production and perception, neglecting its communicative role. i have focused on this, especially some social and psychobiological objectives. i have combined a general inquiry into the use of unvoiced speech with stimulus-response experiments on particular signal properties. (1) analyses of answers to queries revealed that judgments about whispering depend on the social contexts. in the private domain it plays a clearly positive role, but in the public domain it is more problematical. two causative factors were identified as relevant: (a) an 'ingroup' function of whispering which could induce negative 'outgroup' effects in co-listeners, and (b) a psychobiological component of whispering which could affect the auditory vigilance of co-listeners who were not addressed personally by the signaling, but often wanted to understand a whispered message. (2) analyses of experimental data confirmed the relevance of these factors. additionally, they showed that unvoiced speech has a limited transmission range, and is easily masked by background noise. taken together, the results suggest that whispering is explained best as a close-distance signal adapted for private use among partners.