Beamforming directs the signals on transmitters and receivers with multiple antennas to improve transmission speed. It is accomplished by detecting the signals and sending feedback to the transmitter to adjust the phase and amplitude of the signals at its antennas. Starting with the 802.11ac version of Wi-Fi, beamforming was standardized for vendor interoperability (see 802.11ac).Beamforming can also work with receiving devices only. For example, certain hearing aids can be configured to emphasize sound coming directly in front or from the left or right. See MIMO and antenna diversity.