Distinctive features refer to a trait that distinguishes one speech sound from another. For example, at the articulatory level, the difference between /s/ and /z/ is the voicing. At the phonetic level, that is, the physical manifestation of the signal in instrumental analysis (phonetic), the /s/ has concentration of energy in the high frequency region as opposed to the voiced /z/. Such features were thought to help the listener distinguish between these minimal pairs in perception. But please note that other pairs may have the same phonetic features even though the ear identifies them as different. Therefore, phonetic features do not necessarily have phonological relevance.