Outer and middle ear transfer function determines loudness across frequency.

Evidence

The outer ear primarily consists of the pinna and ear canal. The components of the pinna and ear canal, together, amplify incoming sound, predominantly for frequencies ranging between 2000 and 3500 Hz (Shaw, 1974). The tympanic membrane lies at the end of the ear canal and vibrates in response to the incoming (and now amplified) sound. The middle ear transmits the vibrations of the tympanic membrane to the cochlea, via the ossicular chain, which consists of the malleus, incus, and stapes and serves to provide an impedance match between the air-filled communication medium and the fluid-filled cochlea. The ossicular chain provides a second source of amplification, with an emphasis on frequencies between 600 and 1800 Hz (Kurokawa & Goode, 1995). — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 212 (#corroborates, via linked claim)

Loudness is the perceptual correlate of sound level. But it is also dependent on frequency, incident angle, the duration of the signal and its temporal envelope. It is one of many psychoacoustic relationships that defy simple descriptions. Yet, one must start somewhere, and so most investigators focused on pure tones in acoustically simple circumstances, like headphone or anechoic listening. — Toole, Floyd E, Sound reproduction- the acoustics and…, 903 (#qualifies, via linked claim)

Categorization

• XREF: connects to: Middle ear impedance match is optimal near 1 kHz; Frequency-domain analysis mirrors how the human ear processes sound — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 377; SOAE bouncing is not caused by middle-ear impedance changes (+6 more)

Broader Connections

• Outer and middle ear structures provide frequency-specific amplification of incoming sound #corroborates (0.95) — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 212
• Loudness depends on frequency, angle, duration, and envelope, not just level #qualifies (0.85) — Toole, Floyd E, Sound reproduction- the acoustics and…, 903
• Head-related transfer functions are measured with in-ear microphones in anechoic chambers #expands (0.80) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1410
• The ear’s frequency response is level-dependent, favoring mid frequencies at low volume #expands (0.80)