Half-intensity depth, and Impedance Flashcards Preview

Physics 110 Exam 2 > Half-intensity depth, and Impedance > Flashcards

Flashcards in Half-intensity depth, and Impedance Deck (14)
Loading flashcards...
1

What is half-intensity depth, (HID)?

The depth of tissue that results in 3 dB of attenuation to the intensity.

OR:

The distance sound travels in a tissue that reduces the intensity of sound to one-half its original value.

 

2

Name some half-intensity depth synonyms:

Penetration depth, depth of penetration, and

half-boundary layer

3

What are the units of half-intensity depth?

Always 3 dB of attenuation

4

How do you set up an attenuation problem?

Set up: Actual attenuation = coefficient x depth x frequency. Then: Solve for unknown.

Ex: dB = 0.5 x cm x MHz

5

As frequency decreases, depth of penetration ______.

Increases

6

As path length increases, the half boundary

layer _____ __ ____.

Remains the same

7

Impedance is associated with ___ __ _____.

Only the medium

8

As the path length increases, the attenuation coefficient of ultrasound in soft tissue:_______?

[increases, decreases, remains the same].

Remains the same

9

Acoustic impedance = _____ x _____.

Impedance (rayls) = density (kg/m3) x propagation speed (m/s)

10

Impedance is important in _____ at boundaries.

Reflections

11

What is impedance?

The acoustic resistance to sound travelling in a medium.

12

How do you calculate acoustic impedance?

Multiply the density of a medium by the speed at which sound travels in the medium.

13

What are the units of impedance?

Rayls. Impedance is often represented by the letter Z.

14

Impedance is determined by: _____?

Medium only.

It is calculated, not measured.