allophone
Linguistics term: a variant pronunciation of a phoneme that does not change meaning. Used in academic or technical contexts.
In Japanese, the moraic nasal ん has multiple allophones.
strange noise; unusual sound
General term for an odd, unfamiliar, or unexpected sound, often implying something is wrong or out of place.
I heard a strange noise from the engine, so I stopped the car immediately.
heteronym
Compound of 異 (い, 'different, unusual') and 音 (おん, 'sound'). The linguistic sense is a calque from English 'allophone'.