Vocalisation may be voluntary or involuntary, it may vary in tone and different words may be used to describe the different sounds in different species e.g. in the dog: growling, snarling, whimpering, grunting, groaning, whining, yelping, screeching and crying. Characteristic sounds may be produced during a particular physiological function or behaviour e.g. grunting when the reticulum contracts in cattle with traumatic reticulitis or yelping when a dog with a damaged bladder urinates or cry when a lamb with Coccidiosis tries to defaecate. Systematic correlation of vocal patterns, their intensity and duration with other signs of pain have been attempted in only a few situations including castration of piglets (White et al 1995; Weary et al 1998), and circumcision and blood sampling of children. Piglets show a cry of a higher frequency during the most painful stages of castration, compared with the cry they produce when picked up.
Lambs show an increase in the incidence of vocalisation after rubber ring castration and tail docking. They show different types of cry from a groan to a loud cry. Vocalisation with other methods of castration was largely confined to during application of the procedure (Molony et al 1997).