IPhone 4 - iPod app plays music/podcasts with reverb - How do I make it stop?

Question

Hello!
Recently, when I play music or podcasts from my iPhone 4, whether into headphones, from the phone itself, or connected to speakers, it plays it with a sort of echo or reverb. 
It does not do this when I am on speaker phone. 
I can't think of what could be causing this, but I use my iPod often, especially in my car on the long drive to and from work. 
It's kind of creepy sometimes, depending on what's playing, not to mention, just annoying that it's happening in the first place.
Any thoughts on what could be causing this, and how it can be fixed?

Answer 1

CORRECTION:
After Apple gave me a new phone, it worked fine for a while, then the problem started again once I plugged it into the Aux input in my car.  I unplugged it, and tested the phone by itself, still did it.  But only on podcasts.
My husband did some more research and corrected the problem.  Here's what was happening:
When you play podcasts, and you're in the "now playing" screen that's a translucent black, shows volume, where you're at in the podcast, etc.  In the upper right corner of this screen, there is a little white box that says "1x".  Touching this box will allow you to change the speed of the podcast (I guess some people are such avid podcast listeners, that it saves them time to listen to it faster).  I had coincidentally and unknowingly changed the speed of the podcast to "1.1x" which just made it sound funny, not faster. 
He changed it back to "1x", and everything is now hunky dory!  But thanks for the new phone, Apple!  Just wanted to clear that up.  Sorry for the confusion.