Wireless headphones, sometimes called cordless headphones, are small electronic speakers that a user can wear close to his or her ears to listen to sounds provided by a device but that are not connected to the device by wires. The sounds typically are transmitted from a device, such as a digital music player or smartphone, to the headphones using radio frequency waves. Some early versions transmitted the sounds using infrared signals. The headphones can be as large as padded cups that cover the ears or as small as earbuds that fit snugly into the ear canals. Wireless headphones can receive signals up to a certain distance away from the source device — usually at least 100 feet (30.5 m).