English: To generate a psychoacoustical tuning curve, choose any frequency, and lower the amplitude such that the subject can barely detect it (~2dB above threshold). This probe tone will be intermittent. Then, the masker tone is presented at a different frequency, and increase the amplitude as high as possible such that the subject can still detect the probe tone. Repeat the process for multiple frequencies, and derive your line graph. Here, we see two psychoacoustical tuning curves - one for a normal cochlea and one for a cochlea with damaged outer hair cells. Notice that the damaged cochlea is both less sensitive (the line is lower) and less selective (the curve is not sharp). Thus, to restore hearing in someone with outer hair cell damage, simple amplification is not enough, since that raises inaudible, indistinguishable sounds to the level of audible, indistinguishable sounds. The selectivity problem needs to be solved to have useful hearing.