Final answer:
Sound localization is affected by the head shadow effect, which attenuates high-frequency sounds and creates interaural intensity differences. In indoor environments, wave interference from a stereo system can also cause variations in sound intensity.
Step-by-step explanation:
The phenomena in question pertain to sound localization and how the head can create an area of decreased sound intensity, known as the "head shadow." This head shadow causes high-frequency sounds to be attenuated when they reach the ear that is farther from the sound source. This can create an interaural intensity difference, which is one of the cues our brain uses to localize sound in the horizontal plane. The ear closer to the sound source will perceive a louder sound compared to the other ear. Conversely, in an indoor environment where a stereo system is set up, sound reflections and wave interference can occur, leading to zones where sound seems dull due to destructive interference, or excessively loud due to constructive interference.