Sensation of the frequency of a sound wave (number of compressions per second) -> experienced oh how high or low a sound is. Complexity of sound - what makes sounds diff from one another. Structure that we commonly refer to as ear known as -- pinna. Tympanic membrane = ear drum stapes = bones inside ear malleus = bones inside ear. Why is it important for sound vibrations to be amplified as they pass through the ear: more force needed to create fluid vibrations vibrations in the fluid of the cochlea causes: hair cells to displace. The pinna does help us identify the location of a sound. -> helps us localize the source of the sound. -> since they are located right next to ear. Inferior colliculus: similar role of being a receiving point to directing messages to different points.