Presented herein are techniques for increasing sensitivity of a hearing prosthesis to sound signals received from the “side” of a recipient. The sensitivity of the hearing prosthesis to sound signals received from the side of a recipient is provided by a spatial pre-filter that is configured to use a primary reference signal (i.e., a first directional signal) and a side reference signal (i.e., a second directional signal having at least one null directed to the side of the recipient) to calculate a side gain mask. The side gain mask includes gains for each of a plurality of frequency channels associated with the received sound signals.