An output assembly comprises at least one light detector configured for placement under skin near a temporal bone so as to couple with a behind the ear unit coupled with the Pinna. The area of the at least one detector may comprise an area to couple with a light source. As the area of the detector under the skin can be large the at least one detector under the skin can couple efficiently with a light source. An input transducer assembly can be configured to transmit light energy to the output assembly with the multiplexed optical signal through the skin tissue. The multiplexed optical signal may comprise a pulse width modulated signal so as to decrease the effect of non-linearities of the light source and light detector and provide quality sound to the user.
