Some Problems in the Measurement of Cochlear Distortion

Proper specification of the magnitude and purity of the sound stimulus is of utmost importance in studies dealing with distortion processes in the ear. It is shown that, in general, sound pressure level (SPL) measurements in rigid walled couplers do not provide adequate representation of sound levels observed at the experimental animal's eardrum. Similarly, the distortion generated by the experimental apparatus can be either over or underestimated if measured in couplers. It is shown that, in general, the absolute specification of tolerable distortion level created by the experimental apparatus is not possible, and that this level depends on various factors of the actual experiment. Finally, evidence is presented that favors the prosecution of studies on aural distortion with the auditory bulla closed.