It won't fit. The adaptor you linked is for converting two mono sockets into a single stereo socket. The sockets on BA are designed to carry two stereo signals. The larger socket carries the main signal, the smaller one the noise cancelling signal, though I guess this one may be mono. Regardless, unless you have headphones with a similar noise cancelling set-up to BA, the second socket is useless. Superimposing the signal would have a detrimental effect, I think, as I would imagine there is a seperate pair of drivers for the noise cancelling as this is mid/low fregquency only... the ear pads being sufficient to cancel the high frequency. I would imagine the signal expects a crossover for the low frequency drivers, something yer average earphone won't have...

Off topic, but does anyone know where the background noise is sampled for the noise cancellation?