Sanderxpander
Ahhh you may be thinking of Audition which is Adobe software? Audacity is a free open source DAW with some built in noise reduction functions.
Here;
http://audacity.sourceforge.net/

You my friend are absolutely correct.  I knew that I should not have skipped that geritol this morning... Now I guess I will go and take my ole self and huddle up with a goodie powder and rub my feet with some "linament"...

Hi, Sanderxpander and LunaTech,
 
as I stated above, I already tried Audacity but didn't like the results but, anyway, I didn't discard it yet, it runs very fast in my computer, even for these long files.
 
RX3 is in my wishlist for next year.  I won't receive anything for this project as I offered the help for friends.
 
Thanks!!

Audition is no longer offered as standalone  product.  It's subscription only and even that I think is only offered as part of suite.
 
In listening to the file, there are a number of factors at play.  It is very noisy.  Even if the room was empty, it sounds like a very bad on camera mic from far away so the voice is very dull and probably picking up more room reflection than desired.  I tried two quick approaches just to see if there was a quick fix for the noise problem.   This is a quick two pass noise reduction in Audition with a quick filter of the top end:     https://www.dropbox.com/s...sqmnbqabrj/Sample2.mp3
 
It dulled it even more but took away a good chunk of the noise.  With enough time, one could probably do this in a way that gave the voice more sparkle.   
 
This was a quick attempt within Sonar using R-mix and ewq to reduce noise.  Again, i did not attempt to tackle any other issue.  I am going to try this again later when I am not as pressed for time.  I have never considered using two light passes with R-mix, but I suspect that would give me a better result than this.  I pretty much stopped just short of the dreaded robotic artifact point.  Where as the two pass approach in audition gave me a cleaner, if duller end result.  https://www.dropbox.com/s/ifzotynsao8x6ac/sample3.mp3
 
 
I

Hi Atsuko,
 
Noise wise, what you did is good considering the quality of the recordings.  Similar to the audition results.  I'm sure with practice you will be able to make it even better.  The sound does have a slight metallic/robotic type ring, but it is hard to avoid that when the original recording has so much distance from mic to speaker in a large room.  I suggest trying it again on lower setting and making multiple passes and see if that takes off the ringy quality some.
 
For those who are looking for other free/low cost solutions, I was able to get results similar to what I got using R-mix with Spectro by Stillwell.  Not  quite as good as R-mix but Stillwell products offer longer than usual evaluation period, are 64-bit and reasonably priced.

I have an old voice track that I wanted to remove hum and pops from and had remembered seeing many posts where people said they preferred to clean audio in Adobe Audition. I actually have owned this as part of the "Creative Suite" for years but rarely used it.
 
Like the OP, I started searching and tried to use an EQ, but was not effective (I actually had a hum that was getting louder toward the end). I did not try R-MIX, but that may be a viable alternative, as it also had the "spectrum analyzer" look of Audition.
 
After finding this on Adobe's web site (http://help.adobe.com/en_US/audition/cs/using/WS58a04a822e3e5010548241038980c2c5-7f30.html ) I tried out Audition for the first time, and it worked very well (you can grab an area of generic background noise and have it filter an entire track against this)! However, Audition is not free...
 
Michael

Sorry, I chimed in on this one late, I am sure your project is well underway. I have owned Adobe for year, and the "trial" versions of their software is fully functional for 30 days (i.e. Audition). I actually got the trial of Adobe CC to modify some flash work I was doing a month ago to make sure it was updated correctly to the current flash versioning on the streets. A trial version of Audition should be similar.

'Just found this thread and wanted to chime in on iZotope's RX3 -

the "dereverb" and "dialog denoiser" features are new to the Advanced version.

RX3 Advanced is my go-to waveform editor (replacing Sound Forge in my Utilities drop-down menu in Sonar) and is one
truly amazing editor "add-on" to Sonar!
(Save up and get the standard version, then wait for a discounted upgrade path - you won't be sorry!)

I'm thinking that the 128kbps MP3 isn't the best format for detailed cleaning - BUT -
I have yet to try either new feature, both of which might be the ticket on your files.

For "practice", I would like to try it on one of your files.

If you are still working on this project, PM me and I'll get one of those from you for "experimental purposes".

Cheers,
MG

Yes, Dub - I put that sample in my drop box and will try it if he's done with all of the full-length files.

My thought was that if he was still working through them, I'd help by working on one!

RX also features the ability to do batch files, which I've used with great success.
(Nothing too custom - just generic processing.)

IF - all of the lectures were recorded in the same space, from the same spot, with roughly the same number of attendees,
then some gentler settings could be used with the batch feature and make light work of those 40 lectures...!

Regards,
MG