The Collaborative International Dictionary of English v.0.48:

Vocule \Voc"ule\, n. [L. vocula, dim. of vox, vocis, voice.]
   (Phon.)
   A short or weak utterance; a faint or feeble sound, as that
   heard on separating the lips in pronouncing p or b. --Rush.
   -- Voc"u*lar, a.
   [1913 Webster]