Noise and Health
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Function of the Pinna - the Outer Ear
The outer ear, consisting of an ear flap, also known as the auricle and pinna, and the auditory canal (meatus), has the task of catching and guiding the sound to the eardrum (tympanic membrane).
The complex folds of skin and cartilage of the pinna, the visible fleshy part of the outer ear, are attached to the skull by ligaments and muscles. The ear lobe (lobule) is the only part not supported by the framework.
They may look like it, but the folds are not a mad and random act of evolution/creation. The ‘hills’ and valleys’ of the pinna interfere with sound and modify the spectrum. One may also describe the pinna as a form of audio filter.
The funnel-
Humans have two ears for a reason. The sound arrives at a speed of around 330 metres or 1,070 feet per second. This is faster than an airliner flies at full throttle. Nevertheless, our ears, together with the brain, can compute minuscule time differences and variations in sound pressure level at each ear.
Another cue to the direction of a sound source is the difference in sound reflection, diffraction and absorption on the shoulders, head and the folds of the pinna. These processes lower the intensity and change the spectrum of the sound. In other words, the sound or the noise is not quite the same in both ears.
By turning the head towards the sound we can eliminate the differences and home in on the direction from where the sound is coming from. This process is known as binaural hearing. The brain’s interpretation of the sound signals gives us also an idea of the distance to the sound source.
The amplified and modified sound now flows into the auditory canal, a tube which
is about 2-
Picture source: Wikipedia