Yes and no. I believe loud buzzing like that is due to unshielded or poorly-shielded cabling; so, if you cheaped out on your SNES video cable, that may be why. I got this kind of buzzing when I ordered the basic $6 SCART cable from Behar Bros when I ordered my Toro for my Dreamcast, and it was significantly reduced when I replaced it with one of those shielded Kabeldirekt SCART cables on the US Amazon.
That said, since you’re using the analog audio output, there will always be some level of buzzing (analog noise floor), which will be noticeable when you turn up the volume when no audio is playing.
And then perhaps the best way to get audio out of the SNES, barring a native HDMI mod (none of which exist at this point, to my knowledge), would be a TOSLINK mod, which gets you digital audio output over an optical cable, which means no interference from other cabling and no analog noise floor, but potentially means audio jitter (which I have never noticed using TOSLINK on my other consoles).