HIss is white or pink noise.

Tape hiss lies somewhere in between white and pink, typically leaning towards the white side. Websearch the terms.

Not a single frequency at all, but covers the entire spectrum as tiny pulses that, when heard together, sounds like the rush to our ears.

There are, however noise removal algorithms that may or may not work without leaving digital artifacts behind. One such that may work is the PGVinyl plugin, James designed it for use with vinyl records, but it does have a noise reduction algo in there. There are other plugins as well, some designed specifically for reducing tape hiss, a websearch might bring something up.


--Mac