Final approach to model the effects of fluid in the middle ear. Left: Acoustic input impedance at the eardrum Z_D and eardrum acoustic shunt impedance Z_ac for different factors of eardrum area. Middle: Ear canal impedance for different factors of eardrum area resulting from the model using an ear canal radius of 1.7 mm and an ear canal length of 14 mm. Right: Ear canal impedances measured in infants’ ears with middle ear effusion from [7].