**Core Concept**
The higher auditory centre, also known as the auditory cortex, plays a crucial role in processing complex auditory information. It is responsible for interpreting and understanding various aspects of sound, including its localization.

**Why the Correct Answer is Right**
Sound localization is the ability to determine the source of a sound in space. The higher auditory centre achieves this through the integration of information from both ears, taking into account the time difference and intensity of the sound wave reaching each ear. This process involves the lateralization of sound, where the brain weighs the input from the two ears to pinpoint the sound's origin. The superior olivary complex and the inferior colliculus in the brainstem, as well as the primary auditory cortex, are key structures involved in sound localization.

**Why Each Wrong Option is Incorrect**
**Option A:** Sound frequency is determined by the lower auditory centre, specifically the cochlea and the auditory nerve, which convert sound waves into electrical signals that are transmitted to the brain.
**Option B:** Loudness is also processed by the lower auditory centre, primarily through the cochlea's hair cells, which respond to sound intensity.
**Option C:** Speech discrimination, while a complex function of the auditory system, is not solely determined by the higher auditory centre. It involves a network of brain regions, including the primary and secondary auditory cortices, as well as other areas involved in language processing.

**Clinical Pearl / High-Yield Fact**
The ability to localize sound is often impaired in unilateral hearing loss, where the affected ear fails to provide adequate input for sound localization. This can lead to difficulties in understanding speech in noisy environments.

**✓ Correct Answer: D. Sound localization**