Ultrasound

Question 1

Describe Sound

Answer 1

Answer: Sound is simply a pressure wave (a form of mechanical energy) that travels in a longitudinal wave

A sound wave is created when a vibrating object (such as a cone in a speaker) sets the molecules of a medium (such as air) into motion

When the vibrating object contacts a medium, the molecules of the medium are compressed together, creating an area of high pressure. This is called compression

When the vibrating object moves away from the medium, it pulls the molecules of the medium along with it. This creates an area of low pressure called a rarefaction.

Question 2

What is the difference between Frequency, Amplitude and Wavelength?

Answer 2

Frequency is the measure of a pitch.
- It tells us how many cycles occur in a given period of time.
- Measured in Hertz (Hz) or cycles per second

Wavelength is the distance between two identical points on adjacent cycles
- Frequency and wavelength are closely related.
- A higher frequency produces a shorter wavelength
- A lower frequency produces a longer wavelength

Amplitude represents the sound’s loudness (measured in decibels). It is determined by the degree of pressure fluctuations from the displacement of the molecules within the medium.
- A higher amplitude produces a greater pressure change and a louder sound
- A lower amplitude produces a lower pressure change and a softer sound

Question 3

How does sound propagate through tissue?

Answer 3

Answer: Propagation velocity of sound through several mediums relavant to ultrasound:
- Air: 343 m/sec
- Soft tissue: 1,540 m/sec
- Bone: 3,000 - 5,000 m/sec

NOTE: when no medium is present (such as in a vacuum or outer space), there is no sound

Question 4

What is echolocation?

Answer 4

Answer: The use of sound to visualize physical structures.

EXP: Bats use echolocation as the emission of ultrasonic sound waves by chirping and “listening” as the sound waves bounce off nearby objects.

By calculating how long it took the sound to make a roundtrip and the volume of the returning signal, we can determine the nature of objects around us and their position in space.

By emitting different frequencies, the bat can filter out non-essential information while it focuses on vital information