1999 Chevy Lumina Whining from belt under hood

I have been getting this whining "eehh" sound coming from under the hood it appears to be coming from the timing belt. The sound gets louder and more noticeable as I press on the accelerator.

Strange but sometimes it will go away and come back. A mechanic said he didn't hear anything because it was not doing it that day and said there is a tension adjuster that could be doing that.

Should I have the belt replaced? It is about four years old.

Is lubricating the belt recommended?