brumma

Verb

 * 1) to make a deep, humming or growling sound (of for example a bear, an engine, or a fan)
 * 2) to sing monotonously and out of tune (in a low voice)

Usage notes
A deep, "thick," slowly oscillating humming sound. "Growl" is included as a translation as describing a bear as humming or droning sounds off, and "brumma" is often used for bears.