Fig. 4. Nonlinear phenomena at sonic frequencies. (A) Fundamental frequency of audible sound is correlated with the amplitude of the driving air pressure. (B) A small pressure increase at approximately 3.2 s coincides with an eight- to seven mode-locking transition and an increase in the sound level. It is not clear whether the change in pressure is the cause or result of the sudden transition in the oscillatory state and amplitude. (C) Period doubling, frequency jumps and chaos with a low audible fundamental frequency (f₀). Click-like spikes in sound indicated by diagonal arrows are artifacts caused by flexing of a plastic membrane that sealed the open end of a centrifuge tube around the frog's neck. All data are from frog #4. 1 cmH₂O=98 Pa.