I'm not sure who coined the term, but ear fatigue is simply pain in the ears caused by poor fitting ear tips or it can sometimes occur when you've had your earphones in for a long time - too long perhaps. The principle cause is that most people satisfy themselves with whatever the closest fit is of the three sizes of ear tips that came with their earphones, but that's not always a good idea. Stock ear tips in small, medium, and large are usually made in intervals of 2mm so one size will typically be usable, but usable and comfortable are not always the same thing. All ear tips, whether they be made out of silicone, memory foam, or have some unique shape like a triple flange ear tip all work the same way, they go inside your ear canal and stay in due to friction created by the pressure of the ear tip trying to expand back to its original form. Sometimes you must take a tip that is too large for you and push it in a little farther than is comfortable because the size below it goes in deep but just isn't wide enough to get a good seal, and the result is ear fatigue is as little as a few minutes. Using a size that is more comfortable but doesn't seal well denigrates the sound quality of the earphone. "Tinny" sounding earphones are often just good earphones that have a weak seal in the ear canal and don't isolate as they must to get the full sound they are capable of. The solution is to try a multitude of sizes until you find one that fits your earphones connection and fits your ear. We make 5 sizes in the most common connection diameter (our size 4 model) to overcome this problem, but we also have a number of choices and styles in our various connection diameters that will still be labelled Small, Medium, and Large, but have a different outside diameter from their counterparts in the same connection size. If you are experiencing ear fatigue, the best thing to do is try a number of styles of ear tips to find the best fit. And by the way, there is no rule that says you have to wear the same size in both ears. Many people have different size ear canals, so experiment with that idea too. Once you find the right combination of isolation and comfort, you'll be prepared with all you need to get the most enjoyment out of your earphones. Thanks for stopping by earphonesplus.com today!