What is the main reason behind paracusis Willis in conductive deafness or in otosclerosis patient?

 What is the main reason behind paracusis Willis in conductive deafness or in otosclerosis patient?

Many patients (20%-78%) with otosclerosis have increased understanding of speech during a cocktail party, the so called paracusis of Willis. This phenomenon occurs because the conductive hearing loss attenuates the background noise and renders the dynamic range of the ear at the level of the speaker’s voice, thus effectively increasing the signal to noise ratio.

                                                                                            paracusis Willis Ability to hear a conversation batter in a noisy environment then in a quiet one.