Work on spike in sound machine's output (4,5)

I believe the answer is:

pink noise

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'sound machine's output' is the definition.
I know nothing about this answer so I cannot judge whether this works.

'work on spike in' is the wordplay.
'work' indicates anagramming the letters.
'on'+'spike'+'in'='onspikein'
'onspikein' with letters rearranged gives 'PINK NOISE'.

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