Terrible echo suddenly on Text-to-Speech

Hi, I'm a text editor and I rely heavily on having text-to-speech, specifically the Alex voice, to read back to me when my eyes need a break. After being on Mavericks for a while, my 2008 iMac started producing an echo on the voice; I figured it was yet another sign that the machine was dying, but but now my brand-spanking new MacbookPro has started doing the same thing. It is happening across programs (Word, Chrome, Gmail, Pages, Safari) and it seems to come and go. There was no echo for the first week I had the new laptop, but now it's almost constant, but not entirely consistent. It sounds like he's talking in a stadium. Alex and I have had a long and productive relationships--Anyone have a solution for bringing him back?

Echoing is almost always caused by signal delay and feedback. Are there any other sound pickup devices that you have close by the iMac and or the MacBook Pro? Such as another set of speakers or an open mike?

Thanks for the reply. I did check that all the blue tooth speakers are unpaired, and that did not help. However, someone over on the Apple forum suggested going back to preferences and turning off the quick key command that I had set up (I use command+5) to initiated text-to-speech, and lo and behold, Alex is back to his old charming voice.. The weird thing is that even with "speak selected text when key is press" unselected in preferences, my od quick key command still works.