Can formant shifts and effort cues enhance boundary tone perception in whispered speech?

Whispered speech holds cues to speech melody, in
spite of the absence of F0. Shifts in the locations of
formant peaks have been forwarded as a main cue.
Whispering speakers, however, may convey high
versus low boundary tones signalling questions
versus statements without shifting their formants.
Would the addition of formant shifts enhance these
natural productions and improve question/statement
classification in whisper? Moreover, multiple
acoustic correlates tend to vary with pitch or
intonation conditions in whispered speech, and may
function as listener cues. Here, an attempt was made
to better understand the function of one of these
‘secondary’ cues: intensity. Results show that
formant shifts may improve performance, but not
dramatically, and that intensity seems more useful
when coding increased effort than when being
higher across the board to compensate for reduced
audibility in whisper