The Collaborative International Dictionary of English v.0.48:

Stentorian \Sten*to"ri*an\, a. [L. stentoreus; cf. Gr. ?.]
   Of or pertaining to a stentor; extremely loud; powerful; as,
   a stentorian voice; stentorian lungs.
   [1913 Webster]

WordNet (r) 3.0 (2006):

stentorian
    adj 1: used of the voice [syn: booming, stentorian]

Moby Thesaurus II by Grady Ward, 1.0:

39 Moby Thesaurus words for "stentorian":
   blaring, boanergean, booming, brazen-mouthed, clamorous, deafening,
   ear-piercing, ear-rending, ear-splitting, earsplitting,
   earthshaking, forte, fortissimo, full, full-throated, gravelly,
   loud, loud-sounding, loud-voiced, loudish, loudmouthed, orotund,
   pealing, piercing, plangent, resounding, ringing, roaring, rough,
   sonorous, stentoraphonic, stentorious, thunderous, tonitruant,
   tonitruous, trumpet-tongued, trumpet-voiced, vociferous,
   window-rattling