Yes. The original meaning of "winnow" is:
1.
a. trans. To expose (grain or other substances) to the wind or to a
current of air so that the lighter particles (as chaff or other
refuse matter) are separated or blown away; to clear of refuse
material by this method.
That has been extended to mean:
To separate (the valuable part from the worthless); (now esp. with
out) to extract, select, or obtain (something desirable) by such
separation.
However, Joyce seems to have used it to mean that a desirable feature,
vigour, has been removed from his voice.
--
Peter Duncanson, UK
(in alt.usage.english)