Split audio into left and right channel.

hi! I've seen in this http://forums.ni.com/t5/LabVIEW/Split-audio-into-left-and-right-channel/td-p/1635312and i did it as he says too,but i find some question in it,i used the vi ,but When I send a signal to oscilloscope From the headphone(In order to verify the left and right channel output signal can be different, I will one sinusoidal waveform into a cosine waveform),but i But the oscilloscope display of the X, the Y signal is the same,so i cann't understand ,I hope you tell me the reasons for this situation,thank you very much,