Very easy to do this. Just plonk an ‘ambient sound’ in the level, set the sound to play in the details and make these two changes:
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Check ‘Override attenuation’
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In the attenuation distance section change the Inner Radius and Falloff Distance to 250 ( to get a pronounced effect ).
You’ll find you can only hear the sound when you’re near the actor, and you can place as many of these in your level to get the effect you want 