An experiment to find the acoustic impedance of paraffin and water
Abstract
The speed of sound through paraffin and water was measured, and came close to the generally expected value. The speed in was calculated as 1458.36±16.2ms^(-1) in water and 1212±23.7ms^(-1) in paraffin. Then the density of these two liquids was measured, and combined with the speed of sound to find the acoustic impedance. . The acoustic impedance of water was 1575±29kgm^(-2) s^(-1) and the acoustic impedance of paraffin was 1066.6±32kgm^(-2) s^(-1) . To check that these values were correct the reflection coefficient of a boundary between paraffin and water was calculated using the acoustic impedances of the liquid, then found by comparing the amplitudes of the transmitted and reflected waves. The values were 0.192±0.02 and 0.13±0.02, which are close enough to each other to validate that the acoustic impedances measured are quite accurate.
introduction
When a wave travelling through a material hits a boundary with another material it is affected by the boundary and some of it will be reflected back. How much is reflected back depends on the acoustic impedance of the materials at the boundary.
This experiment will find, experimentally, the acoustic impedance of paraffin and water. This will be done by measuring the density of these materials and the speed of sound through them. The values obtained for the acoustic impedance will be used to find the reflection coefficient of the boundary. This value will be checked by measuring the amplitude of reflected waves off a boundary and then finding the reflection coefficient from these measurements. If the two values obtained for the reflection coefficient are close, then the acoustic impedance measurement...
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...for the acoustic impedance of paraffin and water, the reflection coefficient between paraffin and water was calculated to be 0.192±0.02 . By observing the reflected amplitude of the waves from the boundary, the reflection coefficient was again calculated; but in this calculation its value was 0.13±0.02. These two values are very nearly within each other’s error bounds, but there is still a slight discrepancy. This discrepancy is hard to explain, but it could be due to changes in temperatures in the room or just larger errors involved than was thought during the experiment. The second calculation for the reflection coefficient is probably closer to the true value because less measurements were taken for its calculation.
Works Cited
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The Scholar: I think that's more a function of sound wave vibration than anything else.
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