It's a pressure wave and not a projectile or a waveform. There isn't enough length or width in the tube etc to discuss which direction a wave travels. The half wave of 15 khz is already a centimeter long. I didn't mean to get into a physics discussion. Never mind. Somebody else compare with the more revealing gray filters and report back. Until then, Happy Holidays.
Edited by goodvibes - 12/22/11 at 4:54pm