Question

Please answer all of these questions with brief explanations. Thank you!

Name: Doppler ultrasound PROBLEM 4-8 points Ultrasound is the name we give to sound waves that have a higher frequency than 20 kHz, which is the maximum frequency our ears can respond to. For this problem, assume that high frequency sound waves travel through human tissue at 1500 m/s (about the speed of sound in water). 2 points] (a) Ultrasound equipment for diagnostic imaging typically uses frequencies between 1 MHz and 10 MHz. What is the range of wavelengths in human tissue for sound waves in this frequency range? How does that compare to the diameter of a human aorta? [1 point] (b) Based on this paper https://www.ncbi.nlm.nih.gov/pubmed/6695664 published in 1984, measurements of the blood flow in the ascending aorta shows a maximum speed of 92.00 cm/sec. Assuming the ultrasound frequency used is 2.000000 MHz (the paper uses 2.25 MHz), calculate the frequency as seen by the blood that is traveling toward the ultrasound transducer at 92.00 cm/s. The transducer, which both transmits and receives the sound waves, is not moving. It's fine to use lots of significant figures here, so you can see the difference in frequency. 2 points] (c) Now, calculate the shift in frequency for the waves received by the transducer after the waves have reflected off the flowing blood back to the transducer. The shift in frequency is the difference in frequency between the incoming and outgoing waves. 2 points] (d) The transducer is then re-positioned so that the blood is flowing away from the transducer. Again, calculate the shift in frequency for the waves received by the transducer after the waves have reflected off the flowing blood back to the transducer. [1 point] (e) For (d), calculate the magnitude of the percentage difference between the incoming and outgoing frequencies. (It's essentially the same magnitude for part (c), too, because the speed of the blood is so much smaller than the speed of sound.)

Answer 1

Waveluyan t = velocity 2 2000000-1 s2-200 24 64.35% Difterence 2454-2452 Xloo