Week 1 Ch.1-3

Front 1

Directly Related

Back 1

An increase in one variable results in an increase in the other

• stiffness and speed are directly related

Stiffness⬆ Speed ⬆

Front 2

Inversely Related

Back 2

An increase and one result in a decrease of the other

• density and speed are inversely related

Density ⬆ Speed ⬇

• period is inversely related to frequency

Frequency ⬆ Period ⬇

Front 3

Reciprocal relationship

Back 3

When variables are inversely related in an exact way instead of in a general manner

Front 4

Cosine

Back 4

Ratio of the length of site adjacent to the angle of the hypotenuse

Adjacent/ hypotenuse

Front 5

Sine

Back 5

Ratio of the lengths of the side opposite the angle of the hypotenuse

Opposite/ hypotenuse

Front 6

Wave

Back 6

A wave is a traveling variation and one or more quantities, such as pressure, density, & vibrations. There are two basic types wave transverse and longitudinal

Front 7

Sound

Back 7

Sound of something that travels through a medium. That "something" is traveling variations and pressure.

- sound is a wave

- mechanical

Front 8

Tan

Back 8

Ratio of the length of the side opposite the angle to the side adjacent to the angle

Sine/ cosine = opposite over adjacent

Front 9

Acoustic variables

Back 9

Three quantities that defines sound waves.

- pressure

- density

- particle vibration (distance)

Front 10

Pressure

Back 10

Concentration of force in an area.

• varies with time as the wave moves through the medium

Unit: pascals (Pa)

Front 11

Density

Back 11

Concentration of mass and the volume

Units: kg/cm^3

Front 12

Sound waves

Back 12

Sound propagates through air or other mediums as a longitudinal wave in which the mechanical vibration constituting the wave occurs along the direction of the propagation of the wave.

-Generated by vibrating objects -Cause alternating compressions and rarefactions in the particles of the medium - the particles move back and forth in the direction of propagation of the wave

Front 13

Particle motion (distance)

Back 13

Distance (measure of particle motion)

Units: cm, ft, mile

Front 14

Longitudinal waves

Back 14

And longitudinal wave particles move along the same direction as the wave they are mechanical waves. They are made up of areas of compression also called condensation and areas of rarefaction.

Front 15

Radiowaves

Back 15

Travels at the speed of light and do not need a medium for propagation. Radiowaves are electromagnetic waves

Front 16

Transverse wave (shear waves)

Back 16

In a transverse wave the motion that constitutes the wave is perpendicular or transverse to the direction in which the wave is moving. They are electromagnetic sources such as a light or radio

• fully ossified bone is the only biological tissue that can cause production of transverse waves

Front 17

Ocean waves

Back 17

Travel slower and are produced by the moon's gravitational force on Earth they are mechanical waves

Front 18

Electromagnetic waves

Back 18

Electromagnetic waves are radio waves, radar, gamma, ultraviolet, infrared, visible light, microwaves, Etc., they do not need a medium for propagation

Front 19

How does sound wave travels

Back 19

The wave travels through the medium by the progressive interaction of individual particles as they oscillate back-and-forth.

The energy in the mechanical wave is transmitted through the motion of these particles

- the medium itself does not move from one place to another

Front 20

Mechanical waves

Back 20

Mechanical waves propagate energy through a medium by cyclic pressure variations, they need a deformable, elastic medium like air, water, or soft tissue

• mechanical waves can be either transverse or longitudinal

Front 21

Fundamentals of waves

Back 21

The fundamentals of waves are audible, ultrasound, and infrasound they have the same properties, they are all mechanical waves and are longitudinal

•Audible ~ 20 - 20k cycles/sec (20-20kHz)

•Ultrasound ~ >20k cycles/sec (20kHz)

•Infrasound~ < 20 cycles/sec (20Hz)

Front 22

Sound

Back 22

Sound can be described as periodic changes and the pressure of medium so they can also be called pressure waves are compression waves.

Front 23

Audible waves (human speech)

Back 23

Human speech are mechanical produced by deformation of air caused by vibration of the vocal cords in the larynx.

Front 24

Mode conversion

Back 24

Is defined as one type of wave motion being converted to another

Front 25

Surface waves

Back 25

Some ways are not simply longitudinal or transverse. Such are classified as surface waves (particle movement restricted to a thin layer at the surface of the medium supporting the waves)

Front 26

Acoustic variables

Back 26

Acoustic variables allowed to identify sound waves from other type of waves, there are three type acoustic variables:

• pressure

•density

•distance

If any one of these AV oscillates rhythmically the wave is a sound wave

Front 27

Interference

Back 27

When two or more waves combine to form a single wave

Front 28

Constructive interference

Back 28

Two in Phase waves form a single wave of Greater amplitude

Front 29

Huygen's principal

Back 29

Every point on a wave front serves as a source of spherical secondary wavelets. The created wavelets will have the same frequency and speed as the original. When these wavelets combined they have an hourglass appearance.

Front 30

Destructive interference

Back 30

2 out of phase waves form a single wave of a lesser amplitude

Front 31

Acoustic parameters

Back 31

Acoustic parameters describe sound waves. There are seven parameters in total:

•Frequency

•Period

•Wavelength

•Speed

•Amplitude

•Intensity

•Power

Front 32

Frequency

Back 32

Is the number of how many complete variations (cycles) pressure (or any other acoustic variable) goes through and one second of time. It is how many occurs in a second. It is measured in hertz (Hz). Determined by the Sound Source only.

• it is important because it affects the resolution and penetration of sonographic images

•ranges from 2MHz-10MHz

Front 33

Period

Back 33

Period is the time it takes for one cycle to occur; it is reported in units of time (seconds). The period is determined by the Sound Source only. It is inversely related to frequency.

• typical value 0.1 to 0.5 microseconds

Period (T)=1/f (MHz)

Front 34

Wavelength

Back 34

Is the length (distance) over which one cycle occurs, the cycle length. Wavelength is measured as distance represented by the symbol Lambda. Important because it relates to detail resolution in an image

• determined by both the source and the medium

•the basic unit is meters

•wavelength=velocity/frequency

•typical value: .10-.08mm

Front 35

Propagation speed

Back 35

Propagation speed of sound is the speed at which a particular value of an acoustic variable moves in a certain medium. It is the velocity at which the wave of the energy moves through the medium.

☆Speed of sound depends on the properties of the medium.

-Stiffness

-Density

-Temperature

•units: meters/second (m/s)

•in body, speed of sound 500 m/s to 4000 m/s

•velocity of ultrasound in soft tissue 1540 m/s

•Wavelength=V(mm/micro.S)/F(MHz)

F=V/wavelength V=F (wavelength)

Front 36

Speed and tissue

Back 36

Air= 330 m/s

Water= 1480 m/s

Metal= 2000-7000 m/s

Front 37

Determining the speed of sound in a medium

Back 37

Front 38

Amplitude

Back 38

Amplitude is the maximum variation that occurs in a constant variable. It is the maximum value minus the normal.

• determined the Sound Source

• amplitude decreases as sound goes through the medium

• amplitude units depend on the acoustic of variable Express

-Pessure: Pascals MPa

-Density: g/cm^2

-Particle motion: cm, in., etc.

Front 39

Power

Back 39

Is the rate at which energy is transferred from one part of the system to another. Is the energy transferred divided by the time required to transfer the energy. As with amplitude power decreases as sound travels through the medium

• determined by the source but can be adjusted by the sonographer

• units: watts (w)

• typical values: 0.004 to 0.090 watts

4 to 90mW

Front 40

Amplitude and Power

Back 40

Amplitude and power are parameters they both describe magnitude of a wave

• power equal to amplitude squared

P=A^2

•Power ⬆ Amplitude ⬆

Front 41

Intensity

Back 41

It is the rate at which energy passes through a unit area. Intensity depends on both power in the beam and the area over which it is applied. Intensity is very important describing sounds sent into the tissue by a transducer and while discussing bioeffects and safety.

• determined by the store change is a sound travels through the tissue

• intensity= Power (P(mW))/ Area (A(cm^2))

Intensity = Power

Intensity= Amplitude^2

Power ⬆Intensity ⬆

Area⬇Intensity ⬆