How Does an Ultrasound Machine Detect Reflected Waves?

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Discussion Overview

The discussion centers on the functioning of ultrasound machines, specifically how they detect reflected sound waves using piezoelectric crystals. Participants explore the mechanisms of sound wave generation and reception, the conversion between mechanical and electrical energy, and the interpretation of signals to produce images.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how the change in electric field relates to wave detection, expressing confusion about the underlying principles.
  • Another participant explains that the piezoelectric crystal acts both as a speaker and a microphone, converting electrical energy to sound and vice versa, referring to this as the reverse piezoelectric effect.
  • Some participants discuss the process of oscillation of sound to produce images, noting that sound waves reflect off surfaces and the time taken for these waves to return to the transducer is used to create images.
  • There is mention of the circuitry in the ultrasound machine that facilitates the conversion of sound to an electric signal, with one participant clarifying their understanding after initial confusion.
  • A participant raises a question about the effect of amplitude changes on the detection process.
  • Another participant inquires about the absorption of high-frequency waves, questioning whether it is related to wavelength.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the technical details of ultrasound operation, with some points being clarified while others remain contested or unresolved. There is no consensus on certain aspects, such as the implications of amplitude changes and the absorption of high-frequency waves.

Contextual Notes

Some participants express confusion about specific technical statements, indicating a need for clearer explanations of the piezoelectric effect and the relationship between sound waves and electric signals. The discussion reveals a range of understanding among participants, with some concepts remaining ambiguous.

Who May Find This Useful

This discussion may be useful for individuals interested in the principles of ultrasound technology, piezoelectric materials, and the conversion of sound to electrical signals, particularly those seeking clarification on these concepts.

Mathysics
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how does ultrasound machine detects the reflected wave?

i have read a bit of information and unfortunately I am still unsure how they detect the wave.

"The rapid shape changes, or vibrations, of the crystals produce sound waves that travel outward. Conversely, when sound or pressure waves hit the crystals, they emit electrical currents. Therefore, the same crystals can be used to send and receive sound waves."

I don't understand how the change in electric field can be related to the detection of the wave. please help
 
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The speaker and microphone are the same thing.
If you put a voltage across the piezo crystal it changes shape and emits a sound, if you change it's shape, by a sound hitting it, it generates a voltage.

This is true of most microphones/speakers
 
mgb_phys said:
The speaker and microphone are the same thing.
If you put a voltage across the piezo crystal it changes shape and emits a sound, if you change it's shape, by a sound hitting it, it generates a voltage.

This is true of most microphones/speakers
So when this happens this is the reverse of the piezoelectric effect? (from mechanical energy to electrical energy.)

And the transducer receives sound wave because of this reverse piezoelectric effect?

also there is the other bit that i don't understand

"the crystal will be changed in the same way as when crystal the crystal was generating ultrasound. In this case the changing crystal will cause a changing electric field to be produced across the crystal"

to be honest, I have no idea what they talk about at all. :(
 
Last edited:
Oscillation of sound to produce an image. Instead of using gamma rays to produce material densities, you use sound to reflect surfaces. When sound is produced by a device and interpreted in a certain way, it can produce images.
 
threadmark said:
Oscillation of sound to produce an image. Instead of using gamma rays to produce material densities, you use sound to reflect surfaces. When sound is produced by a device and interpreted in a certain way, it can produce images.
yes it calculates the time that takes to travel back to the transducer to produce an image.

but i don't really get this staement below "the crystal will be changed in the same way as when crystal the crystal was generating ultrasound. In this case the changing crystal will cause a changing electric field to be produced across the crystal"
 
The crystal is a sensor, it creates vibrations and interprets vibrations. the change from sound to an electric signal is in the circuitry of the machine. The crystal interprets sound to be transmitted over the circuit.
 
threadmark said:
The crystal is a sensor, it creates vibrations and interprets vibrations. the change from sound to an electric signal is in the circuitry of the machine. The crystal interprets sound to be transmitted over the circuit.

oops sorry i understand now thx!
 
just wondering, would the change in amplitude (voltage) has any effect on this?
 
yes?
 
  • #10
hey here is another question :S

When the frequency of the wave is too high it will be absorbed easily? I don't understand why. Is it because of the increase in wavelength?
 

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