Possible Clues:

• Dairy din
• Herd mentality output?
• Sounds from the pasture
• Cattle calls?
• Sounding like a cow
• Cattle yard 12-Down
• Heard from the herd, by the sound of it
• Might the doctor go in, being confused and sounding beastly?
• Low sound?
• It's beastly, by the sound of it