Figure 3: Output level of a hearing aid as curve of the input level with non-linear amplification (thick line) in comparison to the unamplified signal (dotted line). The amplification below the knee-point is 20 dB, above the knee-point of 60 dB it decreases linearly. Above 100 dB, even signal attenuation occurs. The whole amplification process may be described by the initial amplification, the knee-point, and the compression.