Acoustic Velocity

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Questions and Answers

What is the relationship between compressibility and sound velocity?

Compressibility is directly proportional to sound velocity

Compressibility is proportional to the square of sound velocity

Compressibility is inversely proportional to sound velocity (correct)

Compressibility has no effect on sound velocity

How does an increase in density affect sound velocity?

It decreases sound velocity (correct)

It increases sound velocity

It has no effect on sound velocity

It depends on the type of medium

Why does sound travel faster in solids than in gases?

Because gases are lighter

Because solids are less compressible (correct)

Because solids have a higher density

Because solids are more compressible

What determines acoustic velocity?

Both compressibility and density Signup and view all the answers

What is bulk modulus?

A measure of the stiffness of a medium and its resistance to being compressed Signup and view all the answers

What is the relationship between the wavelength and frequency of sound?

v = λf Signup and view all the answers

What happens to the beam when the velocity of ultrasound is higher in the second medium?

It enters the medium at a more oblique angle Signup and view all the answers

What is the main cause of artifacts in clinical ultrasound images?

Refraction Signup and view all the answers

What is the key difference between scattered and reflected ultrasound energy?

Direction of motion Signup and view all the answers

What is Snell's law related to?

Refraction of ultrasound Signup and view all the answers

What happens to the energy of ultrasound when it is scattered?

It decreases in intensity Signup and view all the answers

What is the term used to describe the interaction of ultrasound with small structures?

Scattering Signup and view all the answers

What is the consequence of refraction on the ultrasound beam?

It enters the medium at a different angle Signup and view all the answers

What is the required medium for the propagation of sound waves?

Elastic medium Signup and view all the answers

What is the result of scattering on the ultrasound image?

Low- to mid-level grey tones Signup and view all the answers

What is the direction of displacement of the medium in longitudinal waves?

In the same direction as the direction of the travelling wave Signup and view all the answers

What is the term for the fractional change in volume per unit pressure in units of Pa−1?

Compressibility Signup and view all the answers

What is the unit of measurement for velocity of sound?

m.s-1 Signup and view all the answers

What is the result of the vibration of the vocal cord?

All of the above Signup and view all the answers

What is the term for the transfer of pressure changes from one molecule to another?

Propagation Signup and view all the answers

What is the particle velocity produced by the wave represented by?

u(x,t) Signup and view all the answers

What is the undisturbed mass density of the medium represented by?

o Signup and view all the answers

Study Notes

Wave Characteristics

The wavelength (λ) and frequency (f) of a wave are related by the equation v = λf, where v is the velocity of the wave.

Velocity of Sound

The velocity of sound is dependent on the compressibility and density of the propagation medium.
Density (ρ) impedes sound propagation, and sound velocity is inversely proportional to the square root of density (c ∝ 1/√ρ).
Compressibility (K) also impedes sound propagation, and sound velocity is inversely proportional to the square root of compressibility (c ∝ 1/√K).
Bulk modulus (B) is a measure of the stiffness of a medium and its resistance to being compressed.

Factors Affecting Sound Velocity

Compressibility has a greater effect on sound velocity than density, even though density often changes less than compressibility.
Sound propagates faster in solids (hardly compressed) than in gases (easily compressed).
Sound propagates slower in denser materials (having greater inertia).

Transmission and Refraction

The transmission of sound across an interface is described by the transmission coefficient.
Refraction occurs when the velocity of ultrasound is higher in the second medium, causing the beam to enter at a more oblique angle.
Snell's law describes the relationship between incident and refraction angles.

Scattering

Scattering is the interaction of ultrasound with small structures, resulting in a change in the direction of motion of the ultrasound.
Scattered energy is distributed in all directions, unlike reflected energy which travels in a single direction.
Scattered energy is generally much weaker than reflected energy, resulting in low- to mid-level grey tones in the image.

One-Dimensional Ultrasonic Waves

A pressure plane wave propagating through a homogeneous, non-attenuating fluid medium can be formulated using Euler's equation and the equation of continuity.
The undisturbed mass density of the medium (ρo) and compressibility of the medium (κ) affect the wave propagation.

Vocal Cord and Sound Generation

The sound generated from the mouth is due to the vibrations of the vocal cord.
These vibrations are carried by the molecules present in the mouth, and the motion of the tongue and lips helps to coordinate the sound produced.

Propagation

The pressure changes of vibrating molecules are transferred mechanically to neighboring molecules through an elastic medium, such as a solid, liquid, or gas.
Different media propagate sound differently.

Longitudinal Waves

Longitudinal waves are waves where the displacement of the medium is in the same direction as the direction of the traveling wave.

Compression and Rarefaction

Compression and rarefaction are phases of a longitudinal wave, resulting in pressure changes in the medium.

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Description

Learn about the factors that affect the speed of sound, including density and compressibility of the medium, and how they relate to wavelength and frequency.