Occasionally he caught complex rhythmical patterns racing up and down through the audible spectrum, to vanish at the upper or lower edge of hearing.
It would climb the spectrum and hover at the edge of yellow, and the cycle would reverse itself, the, star would expand and cool, becoming once more a ragged, flame-red cloud….
There are no more uses of "spectrum" in the book.
Show samples from other sources
That a man pleasured could so easily resolve himself to the whole spectrum of acts, indifferent and murderous and humane, and choose with such arbitrary will what he shall have to remember forever and forever.
Chang-rae Lee -- A Gesture Life
His appreciation of growing things became more subtle, turned within a more limited spectrum and gradually Lalla’s visits tapered away.