Headphone experiments reveal auditory abilities that free-field studies cannot expose.

Evidence

Yost illustrated that the ear can use interaural phase cues to lateralize sounds even when there is no environmental time delay. Further confirming the results conducted in the free field, these experiments illustrate that sound lateralization is the most robust for sounds presented at midline (i.e., to the front). Yost and Dye illustrated that the ear has the ability to perceive ILDs regardless of frequency. This finding could not have been easily revealed using free-field studies alone. — Jennifer Lentz, Psychoacoustics- Perception of Normal…, 1531