Noise Detail-Removal Help, Sample Attached

I have a clip of audio(archived radio air checks) which was originally transferred from audio cassette to CD-R back in 1999. I have no information on how this transfer was done(equipment, levels etc). Resulting digital audio has constant static-like hissy (mega sibilant-esque) noise throughout whenever the DJ is speaking. There is no noise present when DJ is not speaking. From recollection DJ notes that this does not match audio quality of original cassette. I am assuming this noise was introduced during the transfer from analog to digital. What exactly is this noise that has been introduced? Is there any hope for this audio? Can this noise be reduced in any significant way? I have attached a sample unaltered wav file(ripped from original CD-R) of the distorted audio. Any help/tips would be appreciated much! Thanks in advance! -SF

The noise came from the original radio broadcast (or more accurately weak reception of it), and not the cassette recording. It’s a pretty familiar sort of static, combination of a weak FM signal, and a stronger station on the adjacent channel. If it is just the DJ’s patter you are interested in a low-pass filter with a corner of 2kHz and steep cutoff reduces the noise to a much more tolerable level (but also pretty seriously effects the timbre of her voice). But there isn’t any magic wand we can wave to make it all go away.