Auditory localization is the ability to locate a sound source in the environment, and humans can do this relatively well using hearing alone. We locate sounds using a set of cues. The individual cues are not sufficient in of themselves, but work well when combined together.
These cues are:
Relative intensity. This cue gives us the ability to asses the distance of a sound source, based on how loud it sounds.
Interaural time difference. Neural systems within the brain register minute time differences in specific sound patterns reaching the ears. This cue works best at low frequencies, due to the size of low frequency sound waves.
Interaural level difference. This is a difference in sound intensity due to the head blocking sounds originating at the opposite side of the head, and the intensity will vary depending on which angle it comes from. This cue works best with high frequency sounds.
Filtration effects. There are qualitative differences in sound entering the ear due to the effects of filtration at different points at the head and ear, giving us an assessment of location based on differing filtration effects.
Spectral dampening. Due to the sound absorbing qualities of air, higher frequencies are dampened to a greater degree, and are therefore dampened to a greater degree when travelling longer distances.
Spectral reflection differences. Different frequencies are reflected in different amounts, giving us an additional cue for assessing the location of a sound source. Lower frequencies will reach the hearing apparatus more directly, while higher frequencies will reflect to a greater degree from objects in the environment.