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Biological Sciences
Jason Brown

SLIDE 2When muscles contract they produce a sound This was discovered in the late 1600sFor 2 centuries no one mentioned it again until Wollaston came along He described 2methods to estimate the frequency of the sound that muscles produceThe first method was you take a thumb and stick it in an ear and clench your fist to hear a soundWhat causes this sound is the slight changes in the muscle when it contracts When a muscle contracts its length shortens and its width increases and these changes generate frequency that you can hearThis method is being used as a noninvasive way at looking at problems of the musclesAcoustic myogrpahy is used to listen to those muscle sounds You can detect certain muscular disorders because they cause changes in the sound those muscles makeSLIDE 3The fact that you can hear the muscle sounds is because the human hearing rate is in the range is somewhere around 2020000 hertz where a hertz is cycles per second This means if you stick your thumb in your ear and clench there has to be at least 20 vibrations or as many as 20000 vibrations from that muscle in order for you to detect that soundSLIDE 4When youre talking about muscles and their ability to make sounds in order to make sounds they need to be able to contract with a particular frequencySo to make sound if a muscle wants to move an object and make a sound that you can hear that muscle has to contract and relax at least 20 times every second and up to as high as 20000The thing responsible for making the sound for grasshoppers when it comes to stridulation is what we call a file and scraper system The grasshoppers have pegs along the inside of their hind legs and it contracts its legs up and down until the pegs drag across a very hard vein on its wing which serves as the scraperEvery time each individual peg is contacted by the wing it makes a little vibration in the air and that vibration is detected as a sound
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