I suppose that the answer to that is that you are always your own test pilot. So many variables, shape of your helmet, sensitivity to noise, large hairy ears etc. For non helmet wearers, going the Bradley Wiggins route and cultivating your own might have the same effect for free. I used to wear a helmet at times and found it noticeably noisy in certain circumstances, most likely due to having straps which disturbed the airflow close to my ears. So cat ears, or anything which reduces that disturbance in theory ought to work. But, YMMV!