These high-pitched sounds no longer exist with Canon Speedlites. The last ones with a whistling sound were Speedlite 380EX, 420EX and 550EX. All the newer ones are almost silent.

I have not noticed any special noises. I know this whistling sound from old flash units as well. I hear the high frequencies, like marten devices, quite well.

My four flashes work quietly and reliably. My hearing is not yet so old that I would no longer hear high frequencies ;)