Cats And Dogs Whispering

In normal speech, the vocal cords alternate between states of voice and voicelessness. In whispering, only the voicing changes, so that the vocal cords alternate between whisper and voicelessness (though the acoustic difference between the two states is minimal).
There is no symbol in the IPA for whispered phonation, since it is not used phonemically in any language. However, a sub-dot under phonemically voiced segments is sometimes seen in the literature, as (ʃʊ̣ḍ) for whispered should.