The cell phone radiation studies are out there and you have folk that worry about it and then some that are adverse in their feelings about any RF signals. I won't be addressing that.
But small world that it is now, way back when I was in R&D and the engineers there were experimenting with ways to beam form and modulate in the audio range. I won't get into that but if the mass was great enough that it could alter the microwave path and the volume level could move this mass then you could affect the microwave transmission. As to harm, you didn't detail what harm you mean but yes it could cause interference of the transmission.
Interesting stuff and we only tried this in the labs but it never left the labs since you could do the beam forming in other ways much more efficiently.
Could microwaves from wireless iphone speakers do more harm when the volume is turned higher, or does volume not affect microwaves at all?
Thanks for any info.