"I ordered an Sordin electronic ears muff. This product is a new design. When recieved the ears muff, I noticed there is a whistling sound. I called and find out what is going on. They explained that the sound is a feedback sound which is expected when two muffs is close together. I will give it a try a little longer to see what how it will hold up. Shipping is supper fast, they shipped out on the same day."