Yep, the sound changes, but I couldn't hear it at first. It took some experience to be able to notice the difference. A good rule of thumb has been to change your needle with every 8 hours of sewing. Now that does not mean you change the needle every day. Those guidlines mean a sewing machine sewing constantly for 8 hrs. While I may spend an entire day sewing, that day also includes pressing seams and trimming and a break now and again. When I find my brand of needles on sale I stock up. The sharper the needle, the less likely the needle will go looking for path of lease resistance when you are aiming for the exact center of two seams, as in star points. Always remember that the better our tools, the better our success. A new sharp blade makes cutting accurate strips a breeze. I always delint my machine and change the needle at the begining of each new project.