Is directionality a significant factor with whistles? Higher or lower pitch in a whistle is still relatively high. IMO a bigger problem is hearing loss for some individuals at certain frequencies.

I recently passed a flight physical and at some frequencies my hearing loss is significant due to thousands of hours of P-3 cabin noise and just hanging around flight lines. I'll bet that a lot of our Mid-East war vets will have similar hearing loss issues albeit for different reasons. That is a more significant issue than the frequency a whistle tweets. $.02