Head and pinna scattering imprint direction-dependent spectral notches onto the ear signal.

Evidence

Due to scattering and reflection caused by the head and the pinna, the magnitude spectrum of the sound entering the ear(s) is dependent on the direction of arrival. These cues are denoted as spectral cues. Spectral cues are important when localizing sound sources in the median plane and its vicinity. To illustrate the spectral cues, the left ear HRTFs measured with a source in different directions in the median plane are shown in Figure 12.13 for four subjects. It can be seen that the HRTFs indeed carry information on direction; there are vast changes in the spectra when the elevation changes. The pinnae of subjects are different, and so are the spectral cues. The figures have similar structures, the arcs have similar shape, but they are located at different frequencies. The notches and humps at 4–10 kHz are also located at different frequency-elevation positions, although some similarities between subjects are evident. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1451

Categorization

• DEFINE: Defines spectral cues as the direction-dependent magnitude spectrum alteration caused by head and pinna scattering.
• XREF: connects to: Head-related transfer functions encode how the head and pinna shape spatial hearing; Head-related transfer functions spatially pan monaural sources by modeling each ear’s directional filter response — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2250; Pinna, head, and torso shapes encode spatial direction into ear-canal sounds — Toole, Floyd E, Sound reproduction- the acoustics and…, 286 (+6 more)

Broader Connections

• Pinna, head, and torso shapes encode spatial direction into ear-canal sounds #expands (0.95) — Toole, Floyd E, Sound reproduction- the acoustics and…, 286
• Head-related transfer functions encode how the head and pinna shape spatial hearing #expands (0.93)
• A low-frequency spectral notch in pinna cues shifts upward with elevation angle #exemplifies (0.90) — Dijk, Pim van, Physiology, Psychoacoustics and…, 3062
• Individual ear shapes give each listener a unique head-related transfer function #expands (0.90) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 736
• Pinna spectral notch frequency increases with sound elevation in the median plane #exemplifies (0.88) — Dijk, Pim van, Physiology, Psychoacoustics and…, 3061
• Head-related transfer functions spatially pan monaural sources by modeling each ear’s directional filter response #expands (0.85) — David M. Howard, Jamie Angus, Acoustics and Psychoacoustics, 2250
• Moving one’s head shifts spectral notches that encode source direction #expands (0.85) — Eric J. Heller, Why You Hear What You Hear- An…, 1936
• Head scattering creates level differences between the two ears’ received signals. #corroborates (0.82)
• The outer ear’s resonant shapes enable front-back sound localization #qualifies (0.78)