Sound waves are converted finally into which of these signals in order to be processed by the brain?

Sound waves are longitudinal wave which propagates in form of compression and rarefaction through the medium

As the medium is have compression and rarefaction then we will have few positions in the medium where we have pressure maximum and few points of less pressure.

this pressure difference creates disturbance into our ear drum and this disturbance or this signal is convey to brain as sound.

The transmission of this signal is always in form of electrical signal which are carried by neurons into our brain

So the sound waves are converted finally into electrical signals in order to be processed by the brain.

at positions a, g kinetic energy is maximum.

at position d, potential energy is maximum.