If the sound generated by the Club-winged Manakin is coming from one wing tip hitting the other, we might expect to hear a series of quick knock-like noises. Instead, we hear a continuous hum. Kim Bostwick found that to make the sound we hear the air is actually vibrating 14 times faster than the wing-knocking that occurs 107 times each second. This must mean that for each time the Club-winged Manakin’s wings come together and spread back apart, something else is happening 14 times. What could be happening? Where could these 14 vibrations be coming from?