Convolution of a mono sound with the MIT HRTF database

I would like to ask how we convolve a mono sound with a pair of hrtf from the MIT Kemar database. when I try to convolve a sound with one of the HRTFs it has an error msg says that:

A and B must be vectors.

I load a sound 'wav'. then I use the readhrtf function. then I am trying to do the convolution and I have this error.

Any ideas?

Thanks