What causes the interaural level difference (ILD)?

What causes the interaural level difference (ILD)?

• A. Pinna filtering at low frequencies
• B. Distance-based attenuation that affects all frequencies
• C. Temporal jitter between ears
• D. Head shadowing that attenuates high-frequency sound.

Answer: (D)

Interaural level differences come from the head acting as a barrier that reduces the sound reaching the far ear. This head shadowing effect is most pronounced for high-frequency sounds because their wavelengths are short enough to be blocked by the head, leading to a noticeable attenuation at the ear opposite the source. At low frequencies, wavelengths are long enough to diffract around the head, so the level difference between ears is small. Temporal differences (ITD) involve timing, not level, and pinna-related effects shape spectral cues more than straightforward level differences. So the main cause of ILD is head shadowing that attenuates high-frequency sound.

Interaural level differences come from the head acting as a barrier that reduces the sound reaching the far ear. This head shadowing effect is most pronounced for high-frequency sounds because their wavelengths are short enough to be blocked by the head, leading to a noticeable attenuation at the ear opposite the source. At low frequencies, wavelengths are long enough to diffract around the head, so the level difference between ears is small. Temporal differences (ITD) involve timing, not level, and pinna-related effects shape spectral cues more than straightforward level differences. So the main cause of ILD is head shadowing that attenuates high-frequency sound.