The eardrum is a single sensor: The sound pressure which vibrates the eardrum propagates as a single signal in the hammer bone which is attached to the inner surface of the eardrum, i.e. there is no several bones which would detect the pressure on different locations of the tympani (which would probably be inefficient anyway).
Direction-dependent mono-aural cues: Horizontal Spatial hearing cues are mainly driven by differences in time and amplitude of the sound wave in the two ears, while vertical spatial hearing is mostly driven by direction-dependant spectral signature of the head and pinae (HRTF).
--> Studies with single-sided deafness individuals show that it is possible to learn to localize sound sources from HRTF cues in the horizontal planes too.
Agterberg MJ, Hol MK, Van Wanrooij MM, Van Opstal AJ, Snik AF. Single-sided deafness and directional hearing: contribution of spectral cues and high-frequency hearing loss in the hearing ear. Front Neurosci. 2014 Jul 4;8:188. doi: 10.3389/fnins.2014.00188. PMID: 25071433; PMCID: PMC4082092:
To investigate whether single-sided deafness listeners rely on monaural pinna-induced spectral-shape cues of their hearing ear for directional hearing, we investigated localization performance for low-pass filtered (LP, <1.5 kHz), high-pass filtered (HP, >3kHz), and broadband (BB, 0.5–20 kHz) noises in the two-dimensional frontal hemifield. We tested whether localization performance of single-sided deafness listeners further deteriorated when the pinna cavities of their hearing ear were filled with a mold that disrupted their spectral-shape cues. [...] Several listeners with single-sided deafness could localize HP and BB sound sources in the horizontal plane [...]. Localization performance of these listeners strongly reduced after diminishing of their spectral pinna-cues.
This literature review about spatial hearing with impaired ear points some laboratory limitations to the above findings:
it will be necessary to show that it extends to more realistic and challenging listening situations than those typically used in the laboratory, and that the benefits include not only a recovery in sound localization accuracy, but also improved speech-in-noise perception.
The Agterberg et al. 2014 paper also reviews the studies with non-human single-sided deafness and how inborn versus later deafness are involved.