[78-L] audio "restoration" question

[Randy Watts]

A question for those of you who know more about audio restoration than I do. (I just clean up the records and listen to 'em.) Someone I know sent me a CD-R of 78s he "restored." Frankly, I thought what he did to them sounded awful. I'd rather have heard them with surface noise, scratch, pops and clicks intact. One thing I'm specifically wondering about is what it is that people do to recordings that creates a very noticeable pumping effect on the volume. I don't know what else to call it. During loud passages, it's not that noticeable, but as the volume of a recording goes up and down, you can hear this effect kicking in and out, sort of like it's mashing down on the sound. The quieter the recording gets the more noticeable it is. I'm not sure how else to describe it. I hear this effect far too often on old radio shows that have had amateur "restorations" and am just curious what causes it. It can make listening to the dialogue on a radio show rather
 difficult, not to mention what it does to musical dynamics.

Thanks,

Randy