A 2 MHz and 5 mW/cm2 ultrasound beam is traversing 10 cm of material having an attenuation of 2 dB/cm. What’s the intensity of the beam after it has passed through this material?
Properties of sound
A sound wave is a mechanical wave (or mechanical vibration) that transit through media such as gas (air), liquid (water), and solid (wood).
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A sound or a sound wave is defined as the energy produced due to the vibrations of particles in a medium. When any medium produces a disturbance or vibrations, it causes a movement in the air particles which produces sound waves. Molecules in the air vibrate about a certain average position and create compressions and rarefactions. This is called pitch which is defined as the frequency of sound. The frequency is defined as the number of oscillations in pressure per second.
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People perceive sound in different ways, like a medico student takes sound as vibration produced by objects reaching the human eardrum. A physicist perceives sound as vibration produced by an object, which produces disturbances in nearby air molecules that travel further. Both of them describe it as vibration generated by an object, the difference is one talks about how it is received and other deals with how it travels and propagates across various mediums.
A 2 MHz and 5 mW/cm2 ultrasound beam is traversing 10 cm of material having an attenuation of 2 dB/cm. What’s the intensity of the beam after it has passed through this material?
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Then, why the answers are different when I use different formulas, dB= 10log (I/ I0) and I= I0 10^-ax?
The first one is 5e-5 W/cm^2 and the second one is 5e-23 W/cm^2.
by Bartleby ExpertIn this question, I know the intensity of incident ultrasound and I know the attenutaion after it passes 10cm material which should be -20 dB. So, I would like to know by using the formula, dB = 10 log (I/ I0), can I directly calculate the I which is the intensity after passing the material by substituting the dB= -20 and I0 = 5 mW/cm2 given in the question?
Like -20 = 10 log( I / 5e-3), I= 5e-5 W/cm^2?
by Bartleby ExpertCan we use the attenuation formula (I = I0 exp -ax) in this question? If yes, how to calculate this? If no, why?
by Bartleby Expert
