Many musicians around the world have developed hearing impairment (too loud music, industrial noise, etc.). Hearing aids only help speech perception but badly distort the timbres of musical instruments. Using DSP we can pre-warp sounds so that music playback sounds correct to them, instead of turning oboes into muted jazz trumpet sounds. The secret is understanding human loudness perception and performing spectral multi-channel nonlinear compression to compensate for degraded hearing. I aim to describe how our perception operates and then how to easily perform the nonlinear compression needed to compensate sensioneural hearing impairment.