Two Distinct Loudness Functions of the Ear

Abstract

A binaural loudness balance was performed using subjects with normal hearing. The reference signal was a pulsed tone, and the balance signal was a steady tone of the identical frequency. The reference tone was presented at intensities of 20, 40, 60, and 80 dB re 0.0002 μbar. The balance tone consisted of a continuously varying intensity (increasing or decreasing) having an attenuation rate of 1, 2, 4, or 8 dB/sec, whose starting intensity was either suprathreshold or infrathreshold. As was anticipated, the different attenuation rates modified the balance point with the closest balance occurring with the use of 8 dB/sec attenuation rate. Suprathreshold starting intensities presented a poorer balance (balance at higher intensity) than did the infrathreshold starting intensities. An unexpected result was the differentiation of the balance levels of the supra- and infrathreshold starting intensities when compared with the various attenuation rates. A balance signal starting from below threshold gave results having a logarithmic relationship to attenuation rate, whereas a starting intensity above threshold yielded balance points having a linear relationship to that of the attenuation rate. It would appear that there are two distinct characteristics in the ear that are dependent upon the starting intensity to which the ear is exposed before performing a particular function.