Anatomy of the Auricle - The auricle is the visible part of the ear outside the head. - It is also known as the pinna. - The developing auricle forms from the auricular hillocks derived from the first and second pharyngeal arches. - Cutaneous sensation to different areas of the auricle is provided by the trigeminal nerve and facial nerve. - Vesicles on the auricle can be seen in herpes infections of the facial nerve.

Functions of the Auricle - The auricle collects sound and amplifies it, directing it to the auditory canal. - It acts as a funnel to collect sound. - The pinnae have a filtering effect that selects sounds in the frequency range of human speech. - The auricle helps in sound localization and provides directional information. - In animals, the pinna collects sound, performs spectral transformations, and aids in vertical sound localization.

Amplification and Modulation - The pinna, tympanic membrane, and middle ear amplify sound by about 10 to 15dB in the frequency range of 1.5kHz to 7kHz. - This amplification can cause inner ear trauma at elevated sound levels. - Non-electrical hearing apparatuses have been studied to protect hearing in loud environments. - These apparatuses fit snugly in the concha and are designed to protect musicians and others in loud environments. - The Institute of Sound and Vibration Research (ISVR) at the University of Southampton has studied these apparatuses.

Notch of Pinna - The pinna has a notch that eliminates a small segment of the frequency spectrum. - It works differently for low and high frequency sounds. - For low frequencies, it acts as a reflector dish, directing sounds towards the ear canal. - For high frequencies, it causes phase cancellation, eliminating certain frequency components. - The pinna notch typically affects sounds around 10kHz and aids in vertical sound localization.

Additional Information - Visible auricles are common in mammals, particularly placental mammals and marsupials. - Marine mammals usually have reduced or no auricles due to sound traveling differently in water. - External auricles are absent in reptiles, amphibians, and birds. - Skin impressions show large auricles in certain extinct mammals. - The pinna can also signal mood and radiate heat in various species.