Head intensity-shading fails below the frequency where head size reaches one-third wavelength

Evidence

When a sound is to the right of a listener, the reflection reduces the sound energy that arrives at the left ear. Consequently, the intensity of the sound reaching the right ear will be much higher than the intensity of the sound reaching the left ear. The reduction in intensity at the ear distant from the source is called head shadow. Note also that the head shadow is greatest when the sound is to one side of the head. As a sound moves around the head from the left ear to the center of the head, the degree of head shadow will decrease. A sound directly in front of a listener will not yield a head shadow, and sound intensity at both ears will be the same. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1454 (#expands, via linked claim)

Whether a sound is reflected or diffracted is determined by its wavelength and the size of the object encountered. The smaller the ratio between wavelength and object size, the greater the reflected sound energy. The wavelength of sound (l) is determined by the frequency of sound and the speed of sound, l =c/f, where c is the speed of sound and f is the frequency of sound in Hz. The speed of sound is roughly a constant, and is approximately 340 m/s. Thus, we observe that the wavelength of sound is inversely proportional to its frequency: Low-frequency sounds have long wavelengths and high-frequency sounds have short wavelengths. Thus, high-frequency sounds are more likely to reflect from objects whereas low-frequency sounds are more likely to diffract around objects. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1450 (#corroborates, via linked claim)

Categorization

• XREF: connects to: Directional hearing resolution is worst near 1.7 kHz where head size equals one wavelength; Head shadow attenuates sound arriving at the far ear unless the source is centered — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1454; Head shading creates interaural level differences used for sound localization — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 726 (+3 more)

Broader Connections

• Head shadow attenuates sound arriving at the far ear unless the source is centered #expands (0.95) — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1454
• Head shadowing gives roughly 6 dB interaural amplitude difference near 1.85 kHz #exemplifies (0.90)
• High-frequency sounds reflect off the head while low-frequency sounds diffract around it #corroborates (0.90) — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1450
• Head shading creates interaural level differences used for sound localization #expands (0.85) — Ville Pulkki, Matti Karjalainen, Communication Acoustics- An…, 726
• Head orientation is necessary because interaural level differences plateau off-midline #corroborates (0.80)