A communication device comprising: a processor; a source interface comprising a first source interface for a first external source and a second source interface for a second external source; a signal generation module comprising a first noise generator for generating one or more noise signals; and an output interface; wherein the processor is configured to: obtain a first input signal via the first source interface; obtain a first complementing signal based on one or more noise signals from the first noise generator; combine the first input signal and the first complementing signal to a first combined signal; apply a first filter function to the first combined signal for provision of a first left output signal and a first right output signal; the first filter function comprising one or more head related transfer functions (HRTF_1_L, HRTF_1_R); obtain a second input signal via the second source interface; obtain a second complementing signal, wherein the second complementing signal is the same as the first complementing signal; combine the second input signal and the second complementing signal to a second combined signal; apply a second filter function to the second combined signal for provision of a second left output signal and a second right output signal; the second filter function comprising one or more head related transfer functions (HRTF_2_L, HRTF_2_R); and output a left output signal and a right output signal via the output interface, wherein the left output signal is based on the first left output signal and the second left output signal, and the right output signal is based on the first right output signal and the second right output signal. a processor; a source interface comprising a first source interface for a first external source and a second source interface for a second external source; a signal generation module comprising a first noise generator for generating one or more noise signals; and an output interface; obtain a first input signal via the first source interface; obtain a first complementing signal based on one or more noise signals from the first noise generator; combine the first input signal and the first complementing signal to a first combined signal; apply a first filter function to the first combined signal for provision of a first left output signal and a first right output signal; the first filter function comprising one or more head related transfer functions (HRTF_1_L, HRTF_1_R); obtain a second input signal via the second source interface; obtain a second complementing signal, wherein the second complementing signal is the same as the first complementing signal; combine the second input signal and the second complementing signal to a second combined signal; apply a second filter function to the second combined signal for provision of a second left output signal and a second right output signal; the second filter function comprising one or more head related transfer functions (HRTF_2_L, HRTF_2_R); and output a left output signal and a right output signal via the output interface, wherein the left output signal is based on the first left output signal and the second left output signal, and the right output signal is based on the first right output signal and the second right output signal.