A:Answer I can't answer this with absolute accuracy, but I've made calls with one, and both earbuds in and did not notice a difference. Is it possible that the buds can sense when one, or both, are in use? You have to watch the battery when making a lot of calls. It seems to drain the battery quicker. The instructions included with the buds leave a lot to be desired, but I'm very pleased with these ear buds.