A compressor is often modeled as

x_out (t) = A tanh[ax_in(t)]

We assume that that the input to the compressor is an audio signal having frequency content in the range 20 ≤ f ≤ 15,000 where frequency is measured in Hz. Select α so that the compressor gives a 6-dB amplitude attenuation at 20 Hz. Denote this value as the reference value α_r. Let A = 1 and plot a family of curves illustrating the compression characteristic for α = 0.5α, 0.75α, 1.0α, 1.25α, and 1.5α. Recognizing that the frequency content of the input signal is negligible for f ≤ 15 Hz, determine a suitable ex-pander characteristic.