Lecture 11

Lecture 11 - How sound is alternated by the environment -...

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How sound is alternated by the environment - Reflection: echoes - Diffraction: sound travels around objects - Refraction: propagation speed increases with density of the medium - Absorption: objects along the sound path can be absorb o Meaning it can be distorted - Attenuation: intensity id reduced away from a course - Transmission: sound can be transmitted between media - Habitat type and height of the speaker can affect how far sound travels o Attenuation is minimal at particular frequencies How hearing works - Sound vibrates tympanic membrane when it enters the ear canal o Bones (incus, malleus, stapes) vibrate the oval window o Basilar membrane distorts the tectorial membrane Stiffness of basilar membrane is altered depending on distance from sound source - Inside cochlea o Basilar membrane with hair cells that shear against the tectorial membrane o Varying the tuning of hair cells get adaptations on how an animal can hear o Hair cells have kinocilium or stereocilium o Physical interaction btw tectorial membrane and kinocilium is what causes you to hear - The frequency of stimulus will vibrate the basilar membrane differentially along its length, this creates a tonotopic map - Modifications or distortions in the tonotopic map lead to different species - Birds and most reptiles have similar ear structures - Amphibians, fish and a few reptiles (turtles) don’t have a basilar membrane A case study: pressure sensitive ears – bats - Bats might be able to detect wires by echo-location - Donald Griffin 1958 o Observed that little brown bats could fly a dark room with wires hung in it without hitting the wires. How do they avoid the wires? o
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Lecture 11 - How sound is alternated by the environment -...

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