I recently found my old pair of Shure e2c in-ear monitors minus the earbud tips. I prefer the memory foam tips that seal out all outside noise. The foam tips made by Shure can be uncomfortable -the foam feels like sandpaper in my ears- and they are expensive! $15-$20 for 5 pair. I have thought for a while about making my own out of ear plugs used in my workplace for ear protection. These earbud tips are practically free since they are made from ear plugs found in virtually any high-noise area. The best part is that when they get old and dirty, just toss 'em out and make yourself some new ones!
Metal-tipped retractable pen
Foam ear plugs
Step 1: Cut the Ear Plugs
Cutting the ear plugs is pretty straightforward. Just make sure your utility knife has a fresh blade in it. You want to cut the plug a couple millimeters longer than the earphone shaft that will receive the earbud. That extra overhang won't interfere with the path of the sound, but it will help the earbud stay in your ear more securely. The ear plug foam is pretty squishy, so you will have to cut them with a sawing motion back and forth, slowly pressing down until you have cut all the way through.
Step 2: Creating the Hole
Flip the ear plug up on end now. Center the metal tip of the pen shaft on the end of the ear plug. Slowly push the pen shaft down, staying centered through the length of the ear plug (see the picture for clarity). Once you feel the pen shaft is properly centered on the ear plug, give it a couple whacks with the hammer. Keep in mind you will probably ruin the pen shaft by doing this. Pull the pen shaft out and now you should have a nice small hole running the length of the ear plug. The stem on my headphones is pretty narrow, so 1 small hole works perfectly. You want the fit to be pretty tight so your new earbud tip doesn't fall off in your ear! But other brands such as Skullcandy have much thicker stems on their earphones, so you may need to repeat this step a couple times to widen the hole so your new tips will fit on.
Step 3: Attach to Your Earphones and Enjoy!
Slip your new earbud tip over the shaft of your earphones. Slide it up as far as it will go. Ensure you have the overhang I spoke of earlier. Not only will the overhang help hold your earphones in your ears, but it also helps keep your ear wax out of the little orifice on your earphones that the sound travels through. Insert your earphones like you would insert ear plugs: Roll the foam tip between your fingers, compacting the foam. Slip the tip into your ear canal and hold it there for a few seconds until the foam re-expands and grips the inside of your ear. Now you can enjoy your music without any interference from outside noises!