Inhuman sound? (3)

I believe the answer is:

hum

I'm a little stuck... Click here to teach me more about this clue!

'sound?' is the definition.
(I know that hum is a more specific form of sound)

'inhuman' is the wordplay.
'HUM' is hidden in amongst the letters.
But, I'm unsure how the hidden word is indicated.

Can you help me to learn more?

(Other definitions for hum that I've seen before include "Sound (of business?)" , "Drone or buzz" , "Sound of a bee" , "Make musical sound with closed lips" , "Smell strongly" .)

I've seen this clue in the Evening Standard.

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