Tympanographic volume measurements of the canine ear.

External ear canal volumes of 50 dogs were measured by tympanography. Comparison between each dog's weight and ear volume revealed a linear increase in volume with increasing weight up to 10 kg. At weights greater than 11 kg, ear volumes did not increase. After ear canal measurement, the tympanic membranes of 30 of the dogs were punctured, permitting determination of the combined volumes of the external ear canal and middle ear. This combined volume increased with increasing weight.