barely audible, the barest, faint, gentle, hushed, low, mere/the merest, soft | fierce, harsh | audible, loud, stage
‘I knew this would happen,’ he said in a stage whisper (= one that he wanted everyone to hear).

hoarse, husky, strangled | awed, excited, urgent | confidential, conspiratorial

above a ~
Their voices were very quiet, hardly above a whisper.

in a ~
They spoke in whispers.

softly | hoarsely, huskily, thickly | fiercely, urgently
‘Come on,’he whispered urgently.

brokenly, shakily, unsteadily | angrily, bitterly, furiously | confidentially, conspiratorially | excitedly | almost, half | back
‘Yes, ’ I whispered back.

can/could only
He could only whisper in reply.

hear sb
She heard him whisper her name.

about
I felt that everyone was whispering about me.

against
‘Hush, ’ he whispered against her hair.

through
‘No, ’ he whispered through gritted teeth.

to
‘Let''s go,’ she whispered to Anne.

whisper sth in/into sb''s ear, whisper sweet nothings
He held her and whispered sweet nothings in her ear.