The ear’s frequency resolution worsens progressively at higher frequencies.

Evidence

The excitation pattern provides a great deal of intuition about the representation of sound by the ear, as it reflects the imperfect frequency selectivity of the ear as well as the changing frequency selectivity with increasing frequencies. The imperfect frequency selectivity of the ear is illustrated by the overall smoothing of the spectrum in the excitation pattern. The frequency effects are also illustrated, as the individual harmonics become more smeared together in the high versus the low frequencies. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 515

Categorization

• DEFINE: The excitation pattern is a running representation of the spectrum; this passage defines what it does — smoothing the spectrum via the ear’s imperfect filters.