Frank J. Wilstach, comp. A Dictionary of Similes. 1916.

Drowsy

Drowsy as the hum of a bag-pipe.
—Anonymous

Drowsy as the clicking of a clock.
—William Cowper

Drowsy as … Andalusian Seville.
—Henry T. Finck

Drowsy voice, like murmur of a leafy sycamore.
—Alexander Smith