Can someone who cannot talk still whistle?
Sounds such as certain phonemes are made merely with the use of air flow and movement of the lips or tongue, without the need for action of the vocal chords. Think of 'f', 's', 't', k in the English language. These are called unvoiced phonemes in phoniatrics (see the phonemic chart). Also, clicking sounds and whistling can be made without use of the vocal chords.