I just saw that I didn't answer your question about impedance. Basically the structures that are subjects for vibrations in the middle ear are bigger than the ones medial it. So when you detect sound waves the frequency, or point of impact is not very high in the middle ear but by passing the vibrations on to the inner ear, more directly, the oval window, stapedius etc. these vibrations remain the same but they're acting on a smaller area, thus becoming more concentrated and suitable for action within the cochlea where you have a fluid and small stereocilia that move along with the fluid, which is becoming turbulent due to the vibration conversion. The movement of the stereocilia (they're tiny tiny hairs) serve as neurotransmitters in that they move and convert the energy provided into a signal that gets forwarded to the auditory nerve and enables us to hear.

Right. So the tympanic reflex works a protection to prevent acoustic fatigue. In case of (loud) noise, when you vocalize for example, the stapedius muscle is involuntarily contracting. The tension in the muscle reduces the signal transmission (and therefore the vibrations) that are passed on to the cochlea. If we would not possess this neat little function we would hear things louder. Worth adding is that when sudden noises occur the muscle is not contracted in order to handle this due to the fact that there is a 10ms transmission "delay" and to reach full tension and therefore full mechanism of effect, the delay is even bigger so it builds up gradually in a matter of milliseconds. It mostly decreases intensity of low frequency sounds.

If it wasn't clear enough this serves as a protection for the organ of corti.

I haven't studied neurophysiology in a long time so bear with me should there be minor mistakes. But to summarise and provide an easier answer: the impedance works as a vibration multiplier that is necessary for the next functions in order - so that you convert sound waves into actual sound.

Tympanic reflex is just protection of chochlea from high pitch sound by contaction of (spedius and tensortympani muscles) and makes the conducting system rigid , don't vibrate with sound vibration.impedance matching is simply conduction of sound wave to internal ear without loss in middle ear .