A hearing aid system includes a Bluetooth enabled sound output device and Bluetooth enabled sound output device. The sound output device has a first processor coupled to a first memory, to a first Bluetooth module, to a sound processing module including an amplifier and a speaker, and to a first power supply. The sound input device has an optional aux jack, and a second processer coupled to a second memory, to a second Bluetooth module selectively Bluetooth linkable with the first Bluetooth module, to a sound input module, and to a second power supply. The sound input device may adjust audio volume level of audio signals to a default level before transmission to the sound output device. A second sound input device may transmit audio signals based to the sound input device, from which the audio signals are transmitted to the sound output device.