The Channels are the routes in the environment for the propagation of the sound waves generated through transduction.
The three boxes of the Effector Unit underscore the complexity of the Speech Mechanism, and the allocation of many body parts and functions to that process.
Once the neural impulses are transduced into sound waves, they are propagated through the environment by two Channels to breach the gap between the speaker and the listener. But why are there two channels in Mysak's model?
For the speaker only, as far as the sound waves are concerned, there are two channels of propagation.