Final answer:
The HRTF is effective for high frequencies because these frequencies have short wavelengths that are absorbed or blocked by the head, creating a distinct spatial audio pattern for the ears to detect.
Step-by-step explanation:
The Head-Related Transfer Function (HRTF) works for high frequencies because high frequencies are better addressed by the HRTF compared to low frequencies. This is due to the fact that high frequencies have short wavelengths, which causes them to be affected by the geometry of the ear and the head, such as diffraction and reflection. Essentially, high frequencies get absorbed or blocked by the head, leading to a distinct pattern of how they reach our ears, which the HRTF can capture, allowing for spatial audio perception and sound source localization.
Option c) 'High frequencies are absorbed by the head' is the correct answer to the question 'Why does the HRTF work for high frequencies?'. This is supported by the biology of hearing, where hair cells located near the base of the basilar membrane respond best to high-frequency sounds, and the physics of sound where high frequencies have short wavelengths. Lastly, humans are particularly sensitive to sounds in the mid-frequency range, where a lot of detail and spatial information can be detected, making the HRTF especially useful for these frequencies.