How to listen to a toddler's lungs with a stethoscope

[lmk1]

About 3 months ago, from a seemingly innocuous cold, my 2 yr old developed pneumonia and started wheezing. I took him to the Dr several times while his lungs sounded "great", then when "oh it's just a little fluid", and then "oh wow, he's wheezing". At no time, did I suspect anything based on what I heard externally from his chest or breathing. I bought a stethoscope so I could hear his breathing better, and know when we have an issue or not, as of course, he may now wheeze again. He just developed a cold with a cough, and I think he sounds fine, but then again, I'm not a Dr. Does anyone know any websites, that have 'sample' wav/mp3 files so I could hear what troubled breathing sounds like for comparison?

The pedi gave us extra Xopenex for "next" time, but I'm a little confused on when to use it...I mean should I use it even if he's not wheezing??? And how can I tell if he's wheezing if I couldn't tell last time?

[not now]

http://www.wilkes.med.ucla.edu/lungintro.htm

Turn the volume up on your computer and click on any of the three options on the left.

[lmk1]

Thank you! Now I have an idea what I'm listening for. I hear him breathe in, but I don't hear the breathing out...so I'll assume that's a good thing...that he's not wheezing? Funny, how every time I asked someone what wheezing sounds like, they say it's like a whistle...but that link really doesn't sound like a whistle...more like the whale song or something!
He's coughing quite a bit today, and I've got my fingers crossed, that there will be no wheezing, but I'll see about taking him in if he's still coughing in a few days, just in case, I don't recognize the wheezing. Do you know if there's always coughing during wheezing?

[lmk1]

I think I was listening in the wrong place ... I was listening too low, so I heard the lungs, and now that I'm listening high, it sounds like wheezing or stridor. We're doing xopenex now, and will take him in tomorrow. This sucks. I was so hoping the wheezing was a one time thing, not an every time thing.