Ultrasound Physics Chapter 1 & 2: Math Basics & Sound Waves

What are the 5 relationship types?

Related, Unrelated, Directly Related, Inversely Related, and Reciprocal

Related (AKA proportional)

2 things are associated, but the relationship isn't specific. ( ex Santa is related to Christmas)

Unrelated

2 items that have nothing to do with one another. ( ex Hair color is unrelated to shoe size)

Directly Related (aka Directly Proportional)

2 items that are associated and when one increases, the other increases as well. When one decreases, the other decreases as well. (Ex Clothing size is directly related to a person's weight)

Inversely Related (aka indirectly Proportional)

2 items that are associated and when one increases, the other decreases. (Ex Golf score is inversely related to skill.)

Reciprocal

2 items that have a special inverse(when 1 ↑, the other ↓) relationship... when you multiply them together, you get 1. (Ex 2 and ½ are reciprocals)

Name the common units

Length: cm, feet, inches

Area: cm^2

Volume: cm^3

Length

The amount of space from one place to another

Area

The amount of space taken up in a 2-dimensional, flat object

Volume

The amount of space taken up in a 3-dimensional object

Increase by a factor" means to

multiply by that number

Decrease by a factor means to?

divide by that number

Name the metric system prefixes from largest to smallest

Giga, Mega, Kilo, Hecto, Deca, Base Unit, Deci, Centi, Milli, Micro, Nano

giga (G) meaning

billion

Prefix and symbol for billion

giga (G)

mega (M) meaning

million

Prefix and symbol for million

mega (M)

kilo (k) meaning

thousand

prefix and symbol for thousand

kilo (k)

hecto (h) meaning

hundred

Prefix and symbol for hundred

hecto (h)

deca (da) meaing

ten

Prefix and symbol for ten

deca (da)

deci (d) meaning

tenth

Prefix and symbol for tenth

deci (d)

centi (c) meaning

hundreth

Prefix and symbol for hundredth

centi (c)

milli (m) meaning

thousandth

Prefix and symbol for thousandth

milli (m)

micro (u) meaning

millionth

Prefix and symbol for millionth

micro (u)

nano (n) meaning

billionth

Prefix and symbol for billionth

nano (n)

Scientific Notation

A method of expressing a very large number as the product of a number between 1 to 10 multiplied by a POWER of 10 ( ex 1,750

1,750.0

1.750

1.750 x 10³)

What is sound?

Sound is a mechanical, longitudinal wave that carries energy, not matter.

Sound waves are mechanical waves so that means them have a _______ in order to exists

A medium

What is a medium?

A substance/particles (Ex. Human tissues, water, gel, air, gas, etc.)

What is sound in relation to a medium

Sound is the vibration of molecules in a medium

What is another word for vibrate

Oscillate

What are the 3 acoustic variables

Pressure, Density, and Distance

What is the definition pressure and what is it's unit?

Concentration of FORCE in an area (Pascals Pa)

What is the definition density and what is it's unit?

MASS per unit of volume (kilograms/centimeter cubed kg/cm³)

What is the definition Particle Motion (Distance) and what is it's unit?

Distance molecules travel in a back and forth motion (centimeters cm and millimeters mm)

Acoustic Variables

Changes in medium that distinguish sound from other waves

What is another word for sound waves?

acoustic waves

What do acoustic variables do?

•help us determine whether we have a sound wave or a different type of wave (ex. Microwave, x-ray, light wave, etc.)

What do we do after we determine it's a sound wave?

We have 7 different characteristics to help us describe the sound wave which are called the Acoustic Parameters

What are the 7 acoustic parameters

Period, frequency, amplitude, power, intensity, wave length, and propagation speed

Sound is a mechanical which means?

It's a longitudinal wave that carries energy, not matter.

Rarefaction

Particles are STRETCHED apart, and are LOW pressure/ LOW density

Compression

Particles are SQUEEZED together, and are HIGH pressure/ HIGH density

Propagation

Transmit or be transmitted in a particular direction or through a medium.

Longitudinal Waves

Particles oscillate in the direction parallel to the wave propagation

Transverse Waves

Particles oscillate in the direction perpendicular to wave propagation

Which way does sound travel?

Sound Travels in a Straight Line

Acoustic Propagation properties

The effects of a medium on a sound wave

Biological Effects

The effects of a sound wave on biological tissue(medium) it passes through

What is a wave?

A wave is a disturbance that transfers energy from one place to another without transferring matter. Waves transfer energy away from the source, or starting place, of the energy.

Interference

When more than one wave of sound is travelling in a medium at the same time, in the same location, they will combine to form a single wave.

What are the 2 types of interference?

Constructive and Destructive

Constructive Interference

When waves are "in-phase" with one another. (This means their compressions & rarefactions are occurring at the same time) this results in a bigger wave than either of the original waves.

Destructive Interference

When waves are "out-of-phase" with one another.

This results in a smaller wave than either of the original waves.

We can have special situation where out-of-phase waves with the same amplitude completely cancel each other out!

What happens if we have 2 waves that are in-phase some places and out-of-phase in some place?

We can have both constructive and destructive interference areas occur.