Tympanogram A depicts middle ear compliance (bold black line) within the normal range (light blue area). Tympanogram B, which is flat and without a peak, depicts the reduced middle ear compliance characteristic of middle ear effusion.
Adapted from: Acoustic Impedance and Admittance: The Measurement of Middle Ear Function, Feldman AS, Wilber LA (Eds), Williams & Wilkins, Baltimore 1976. p.103.