An ultrasonic scan uses the echo waves coming from something moving (such as the beating heart of a fetus) inside the body and the waves that are directly received from the transmitter to form a measurable beat frequency. This allows the speed of the internal structure to be isolated and analyzed. The speed of the ultrasound waves in tissue is about 1540 m/s. What is the beat frequency ?beats detected when waves with a frequency of 3.80 MHz are used to scan a fetal heartbeat (moving at a speed of ±8.50 cm/s)? hint that came with it: In this problem there's a stationary source of ultrasound that reflects sound off of a moving object which then returns back to the ultrasound device to measure the frequency. There are 2 Doppler shifts that need to be considered. First the stationary source and the moving observer. Second, when the sound reflects off, the moving object now becomes the source and the ultrasound device becomes the observer. In this shift, the frequency measured by the observer from the 1st shift becomes the frequency emitted by the source for the 2nd shift. Finally, you will need to change the "positive direction" when you calculate the 2 shifts - it should point from observer to source in each case.
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).
Quality Of Sound
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.
Categories of Sound Wave
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.
An ultrasonic scan uses the echo waves coming from something moving (such as the beating heart of a fetus) inside the body and the waves that are directly received from the transmitter to form a measurable beat frequency. This allows the speed of the internal structure to be isolated and analyzed. The speed of the ultrasound waves in tissue is about 1540 m/s.
What is the beat frequency ?beats detected when waves with a frequency of 3.80 MHz are used to scan a fetal heartbeat (moving at a speed of ±8.50 cm/s)?
hint that came with it:
In this problem there's a stationary source of ultrasound that reflects sound off of a moving object which then returns back to the ultrasound device to measure the frequency. There are 2 Doppler shifts that need to be considered. First the stationary source and the moving observer. Second, when the sound reflects off, the moving object now becomes the source and the ultrasound device becomes the observer. In this shift, the frequency measured by the observer from the 1st shift becomes the frequency emitted by the source for the 2nd shift. Finally, you will need to change the "positive direction" when you calculate the 2 shifts - it should point from observer to source in each case.
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