Effects: Equalization stopped working

Sorry, I posted this request in the general Windows area-it should be here in audio.
I downloaded and started using Audacity yesterday in order to edit a MP3 file of a CD recording (recorded on our stereo system) of a 40 year old cassette tape my late father-in-law made of his trip to Europe (it will eventually narrate his slide show in Photo Story). I am trying to control the percussive “p” “t” etc of his vocal recording (is this called “popping vocals”? I think he used a hand-held mic too close to his mouth). Yesterday I tried the various versions of Equalization on selected segments of the audio and had some improvement. I tried more corrections today on selected segments but the Equalization does not affect the recording (the sound waves do not change their range?). Am I missing something?
Do you have any other ideas of what I can try to control the percussive sound? (I’ve read about Fade-in, FFT filter, Hard Limiter)?
I think Audacity is an incredible program, and am impressed that it is a free download. I will be sure to credit it on our families final DVD of the slide show!
Thank you, Jean

I think I may have posted some thoughts about this on the other section.

Several people make devices that you can plug your microphone into and that remove everything below 100Hz. Some choose 120Hz. While the human voice does have stuff down that low, most of it doesn’t contribute at all to the quality of the voice or the intelligibility. Most of it is room rumble and gut-punching “P Popping” sounds.

If you drag the equalizer window out bigger and bigger, it will give you more and more accuracy.

Don’t just cut everything at 100Hz. Start at around 200 and gradually droop it as it goes down. They sound better like that.