Shoulder reflections create a distinguishable 1-ms delay in head-related impulse responses

Evidence

The change of HRIR in the median plane is shown in Figure 12.8a as a function of the cone of confusion elevation δcc. The peaks caused by the sound arriving along the direct path are located at temporal positions 0.3–0.5 ms, which means that the ear canal is relatively well at the centre of the rotation of the source. Perhaps the most interesting details in the figure are the faint arcs or half-arcs which coincide at 0.5 ms with source directions −45◦and 225◦. The arcs or half-arcs seem to have their apexes at temporal positions of about 1.5 ms, 2.5 ms, and 3.5 ms. The first arc, with apex at 1.5 ms, is caused by the reflection from the shoulders. When the source is above the subject, the sound reaching the shoulders is reflected back to the ears, and thus it travels a distance about 30 cm longer than the direct sound, which causes the 1-ms delay seen in the figure. When the source is lower in the median plane, the extra travel time is shorter, and the shoulder contribution arrives earlier. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1421

Categorization

• DEFINE: Explains how shoulder reflection produces a measurable, systematic delay in HRIRs — a concrete mechanism connecting anatomy to acoustic signal structure.
• XREF: connects to: Shoulder reflections imprint identifiable arcs on measured head-related impulse responses. — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 1421