|MadSci Network: Physics|
Hi Lizzy, The question you ask is a very good one - and I couldn't find any resources to answer the question directly for us so we'll have to do it the hard way. Our ears detect sound, but sound is actually a wave of pressure which is transmitted through the air around us. As the wave encounters our ear it transmits pressure changes to our inner ear. Our ear is very, very sensitive and can detect extremely small changes in pressure. It interprets these pressure changes as the sounds we hear. The higher the pressure (or the harder it pushes against our inner ear), the louder the sound. Normally some mechanical action creates the pressure waves we hear (much like when you move your hand [a mechanical action]in a swimming pool or bathtub and create a wave in the water). Some examples of mechanical actions that create sound waves in the air are vibrating violin strings, the impact of a hammer against a nail or wood, or the vibrations of our own vocal cords. In the case of the popping balloon no mechanical action is required because the pressure wave is bottled up inside the balloon already, waiting to be released. A balloon contains pressurized air which presses out against the sides of the balloon, stretching the sides and allowing the balloon to keep its nice shape. The more air we put into a balloon, the harder we have to blow (the air already inside the balloon is pushing out against the air we want to add to the balloon). Because the air on the inside of the balloon is always pushing out in all directions, when we pop the balloon this pressure escapes. This high pressure "wave" would travel away from where the balloon was to our ear. Our ear would sense this change in pressure - in this case a relatively large change in pressure - and interpret it as a loud sharp "POP" sound (remember, the higher the pressure the louder the sound we "hear"). Another interesting version of this problem is what causes the thunder we hear after lightning strikes. Britannica.com (Encyclopedia Britannica) gives a good description here: http://www.britannica.com/bcom/eb/article/0/0,5716,74210+1+72323,00.ht ml Additionally, they discuss sound waves and our sensitivity to pressure here: http://www.britannica.com/bcom/eb/article/5/0,5716,117555+2+109557,0 0.html Some of the math is difficult but the pictures of wave representations may be helpful. Acoustics is a very challenging area of engineering but can be a lot of fun. Try to learn all the math you can while you are in school because math really is power! I hope this helps. Sincerely, Steven Miller Undergrad - Mechanical Engineering San Diego State University
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