it is also my experience compared to passive salt lamp ( the audible difference here can be a placebo i cannot know) ...
And Schumann generators are more audible than ion generator ...Here i dont consider only mere placebo effect at all and in the case of ion generator either .....
A decent Negative Ion Generator works much better than the Him. Salt Lamp to purify the air. I've had both . I don't think the Him. Salt Lamp is anything more than a Lamp.