Ch 3- Describing Sound Waves

What are the typical values for amplitude?

1 million pascals to 3 million pascals.

What is the period of the earth's rotation around the sun? A) 1 day B) 1 hour C) 1 month D) 1 year

1 year.

What is the speed of sound in soft tissue?

1540 m/s or 1.54 mm/μs or 1.54 km/s. (A mile a second).

Which of the sound waves are infrasonic? A) 4 MHz B) 400 kHz C) 28 Hz D) 2 Hz

2 Hz

What is the frequency range for the human ear and what is this range called?

20 Hz to 20,000 Hz (20kHz) Audible.

Identify the wave that is ultrasonic. A) 400 mHz B) 4MHz C) 28 Hz D) 2 Hz

4 MHz, ( 4,000,000 Hz).

Which of these waves is ultrasonic and most useful in diagnostic sonography? A) 400 MHz B) 4 MHz C) 2 kHz D) 200.000 Hz

4 MHz. The only option that falls into the typical range of frequencies used in diagnostic ultrasound.

What is the typical values for propagation speed?

500 m/s to 4000 m/s *depending on the tissue* in which it is traveling.

Which of the following waves has the longest period? A) 2MHz B) 4,000 Hz C) 6 Hz D) 1 kHz

6 Hz

If the period of a wave is 1/8 second, what is the frequency?

8 Hz. (8 cycles per second or 8/1).

Of the four waves whose periods are listed below, which has the lowest frequency? A) 8 s B) 80 microseconds C) 8 Ms D) 800 ks

8 Ms

Of the four waves whose periods are listed below, which has the highest frequency? A) 8 s B) 80 microseconds C) 8 Ms D) 800 ks

80 microseconds

What is the typical value of period?

*0.06 microseconds (us) to 0.5 microseconds (us)* 6 x 10^ -8 5 x 10 ^ -7

3 bigness parameters

*API* Amplitude Power Intensity

What is power determined by?

*Sound source*, Initial power is determined by the U/S machine. It decreases as it travels through the body. The rate at which it decreases depends on the characteristics of the medium and wave.

As frequency *increases*, period ____.

*decreases*

As frequency *decreases*, period ____.

*increases*

A top is spinning on a table. What is the period of the spinning top? A) 4 pounds B) 8 dollars C) 0.05 seconds D) 3 cm

0.05 seconds. Only answer with appropriate units.

What would the equation for a sound with the frequency of 2MHz has a wavelength of 0.77mm in soft tissue?

0.77(mm)= 1.54mm/2

1/8 X 8 =?

1

Period X Frequency = ?

1

What is wavelength determined by? (Review)

By both medium and sound source.

If the power in a beam is 1 watt and the area is 5 cm^2, what is beams intensity? A) 5 W/cm^2 B) 1 W/cm^2 C) 0.2 W/cm^2 D) 1 watt

C) 0.2 W/cm^2 Intensity = power (W)/area (cm^2) Intensity = 1 watt/5 cm^2 Intensity = 0.2 W/cm^2

What is the wavelength of 3 MHz sound in soft tissue? A) 0.51 m B) 0.51 km C) 0.51 mm D) 0.51 nm E) 0.51 μm

C) 0.51 mm Wavelength = 1.54 mm/frequency (MHz)

A sound beam travels a total of 10 cm in 2 sec. What is the speed of sound? A) 10 cm/sec B) 2 cm/sec C) 5 cm/sec D) 0.2 cm/sec

C) 5 cm/sec 10 cm/2 sec = 5 cm/sec

Which of the following characteristics will create the slowest speed of sound? A) High density, high stiffness B) Low density, high stiffness C) High density, low stiffness D) Low density, low stiffness

C) High density, low stiffness

What is amplitude measured in?

Can have units of any acoustic variables: Pascals (pressure) Density (g/cm^3) Particle Motion (cm, inches, or any distance) Can also be measured in decibles

Name the acoustic variables.

Density, particle motion, and pressure.

How do you calculate the wavelength of a sound wave in soft tissue?

Divide 1.54 mm by the frequency in MHz.

What is the wavelength of a wave with an unknown frequency traveling in soft tissue? A) 0.51 μs B) 0.51 m/s C) 0.51 pascals D) 0.51 watts E) 0.51 mm

E) 0.51 mm. The only possible answer is E because it is the only option with units of distance.

Sonographers use ______ frequency transducers rather than ______ frequency transducer for higher quality pictures.

Higher, Lower

What is the equation for intensity?

I=P/A

When a wave's power is doubled, what happens to the intensity?

It also doubles.

When power and amplitude increase, what happens to intensity?

It also increases. These three parameters are all directly related.

When a wave's amplitude is doubled, what happens to intensity?

It is increased 4 times (2x2=4)

What is the meaning of a flat screen tv with a frame of 120 Hz?

Means the tv displays 120 frames per second

Medium One: density 9/stiffness 6 Medium Two: density 8/stiffness 6 Which medium will have a slower travel time?

Medium One. Since both mediums have the same stiffness, the one with the higher density will have a slower travel time.

What is speed determined by? (Review).

Medium. (Speed & density)

What is the units for propagation speed?

Meters per second, mm/μs, or any distance divided by time.

How is time reported?

Microseconds, second, hours, or days.

Amplitude is measured from the _________ value, to the _________ value.

Middle/undisturbed value, to the max value

Is frequency adjustable?

No.

Is period adjustable?

No.

Is propagation speed adjustable by the sonographer?

No.

Is wavelength adjustable?

No.

What five parameters are initially determined by the sound source?

Period Frequency Amplitude Power Intensity

What are the seven parameters used to describe sound waves?

Period Frequency Amplitude Power Intensity Speed Wavelength

If the frequency of a wave is 12 Hz, what is the period?

Period is 1/12 second.

What is the difference between wavelength and period?

Period refers to the time it takes to complete one cycle. Wavelength is the length or distance of a single cycle.

When you think of a light bulb think of _______.

Power (watts)

What is the equation for the relationship between power and amplitude?

Power is proportional to amplitude squared.

What does the symbol ∝ mean?

Proportional to.

A sonographer increases the amplitude of a wave by a factor of 3. How has the power changed?

Recall that power is *proportional* to the amplitude squared: 3x3=9. *So the power increased 9-fold.*

What special relationship do frequency and period share?

Reciprocal.

If either frequency or period remains constant, what happens to the other?

Remains unchanged.

Complimentary units? Match. A) Kilohertz B) Hertz C) Seconds D) Milliseconds

Seconds and Hertz. Milliseconds and Kilohertz.

Why is wavelength important in U/S?

Shorter wavelengths are created by high frequency sound and produces higher quality images.

What is magnitude?

Size and strength of sound wave

What does the three bigness parameters describe?

Size magnitude and strength of sound wave

What is frequency determined by?

Sound source only.

What is period determine by?

Sound source only.

What is amplitude determined by?

Sound source. however, amp decreases as sound propagates in body.

What is known as the ability of an object to resist compression

Stiffness

What two characteristics determine the speed of sound in a medium?

Stiffness and Density.

What is intensity determined by?

The *sound source* or U/S machine. It also decreases as it travels and the rate at which it decreases depends on characteristics of the wave.

What is intensity?

The concentration of energy in a sound beam. Intensity is how the power in a wave spreads or is distributed in space.

What is peak-to-peak amplitude?

The difference between max values and min values of acoustic variables.

If two media are equally stiff but one of them is more dense what will result?

The media that is more dense will have a slower travel time.

What is propagation speed determined by?

The medium.

What is frequency?

The number of cycles that occur in *one second*

What is power?

The rate of energy transfer or the rate at which work is performed.

What is the source of sound in ultrasound?

The ultrasound system and transducer.

What is density?

The weight of a material. (mass)

What is the relationship between *wavelength* and *frequency*?

They are inversely related. If frequency increases, wavelength decreases.

What is period?

Time from the start of one cycle to the start of the next cycle.

True of False: all three big parameters are directly related?

True

A wave with a frequency of 15,000 MHz is ultrasonic. True or false?

True. 15,000 x 1,000,000 = 15,000,000,000 Hz Ultrasonic sound: wave with a frequency above 20,000 Hz.

Propagation speed does not change as frequency increases. True or false?

True. Propagation speed is only determined by medium.

What are frequencies greater than 20,000 Hz (20 kHz) called?

Ultrasonic or ultrasound. Not heard by humans.

How is frequency reported?

Units per second. (Hz) 1 cycle/second = 1 Hz 1,000 cycles/second = 1kHz 1,000,000 cycles/second = 1 MHz

What is the unit of power?

Watts.

What is known as the distance or length of *one complete cycle*?

Wavelength

What is the only parameter to be determined by *both* sound source and medium?

Wavelength

Is Intensity adjustable?

Yes, initial intensity can be changed.

what other terms describe stiffness?

bulk modulus, elasticity, compressibility.

How are wavelength and period differentiated by?

by their units. wavelength (distance) period(time)

Stiffness and Speed are ______ related.

directly; when Stiffness increases, Speed increases

What are the typical values for frequency?

frequency ranges from 2 MHz to 15 MHz. (2 million to 15 million per second)

What is the relationship between intensity and amplitude? (Equation)

intensity ∝ amplitude^2

What is the relationship between intensity and power? (Equation)

intensity ∝ power

Period and frequency are _________ related to each other.

inversely

How are density and speed related?

inversely related

What are the units for wavelength?

mm, meters, or any other unit of length.

What is known as the rate at which sound travels in a medium (soft tissue)?

propagation speed

All sounds, regardless of the frequency, travels at the _________ speed through any specific ___________.

same speed, medium

The more dense an object is the _______ sound will travel.

slower

Materials that are not stiff and very dense will have the ________ speed.

slowest

The average or typical biological medium is called?

soft tissue

as a general rule, sound travels fastest in

solids, slower in liquids, slowest in gases.

Speed is not affected by the nature of a?

sound wave

What is the formula for propagation speed?

speed (m/s) = frequency (Hz) x wavelength (m)

stiff vs density, which is more important?

stiffness

The rate at which amplitude decreases as sound propagates depends on

the characteristics of both the sound wave and the medium.

What is established by the ultrasound system?

the quantity or level of some parameters

Parameters are determined by the _______ through which the sound is traveling, which is also known as _______.

tissue, medium

Peak-to-peak amplitude is _____ the value of the amplitude.

twice

What are the units for intensity?

watts/square centimeters

The effects of a medium on an ultrasound wave are called _____.

Acoustic propagation properties.

The effects of tissue on sound waves are called _____.

Acoustic propagation properties.

Why is frequency important in ultrasound?

Affects penetration and image quality.

In what order does speed travel in these mediums? (Slowest to fastest). Muscle Air Bone Tendon Fat Soft tissue Blood Tendon

Air (330 m/s)* Lung (500 m/s)* Fat (1450 m/s) Soft tissue (1540 m/s)* (Average) Blood (1560 m/s) Muscle (1600 m/s) Tendon (1700 m/s) Bone (3500 m/s)*

What is described as the bigness of wave. That is the difference between max value and the average.. also, difference between min value and average.

Amplitude

**What three parameters make up magnitude?

Amplitude, power, and intensity.

What is the wavelength of a 2 MHz sound in soft tissue? A) 1.54 mm B) 0.77 mm C) 0.51 mm D) 1.54 km/s E) 3.08 mm

B) 0.77 mm Wavelength = 1.54 mm/frequency (MHz). Wavelength = 1.54 mm/ 2 MHz Wavelength = 0.77 mm

If the intensity remains the same while the power is doubled, what has happened to the beam area? A) Quadrupled B) Doubled C) Halved D) Unchanged

B) Doubled. Intensity = power (W)/area (cm^2) If intensity remains the same, whatever happens to power must also happen to area.

Which of the following characteristics will create the fastest speed of sound? A) High density, high stiffness B) Low density, high stiffness C) High density, low stiffness D) low density, low stiffness

B) Low density, high stiffness

Of the four waves whose frequencies are listed below, which has the shortest period? A) 12 kHz B) 6,000 Hz C) 205 Hz D) 1 kHz

12 kHz

what is the wavelength of *1MHz* sound in soft tissue?

1.54mm

What is the meaning of a sound wave with the frequency of 100 Hz?

100 Hz means 100 *cycles* per second

Identify all of the waves that are inaudible. (Select all that apply). A) 4 MHz B) 400 kHz C) 28 Hz D) 2 Hz

A, B, and D.

What is wavelength determined by?

Both *source and mediium.*

How are amplitude and power related?

Both describe size or magnitude of a wave. Directly related. When one increases, so does the other.

If the power of a wave is halved, the intensity is reduced to one-fourth its original value. True or false?

False. If we halve the power we halve the intensity.

If the amplitude of a wave is increased to 3 times its original value, the intensity is increased by 6 times. True or false?

False. If we triple the amplitude we increase the intensity by a factor of 9.

Propagation speed increases as frequency decreases.

False. Propagation speed is only determined by medium.

Propagation speed increases as frequency decreases. True or false?

False. Propagation speed is only determined by medium.

Propagation speed increases as frequency increases. True or false?

False. Propagation speed is only determined by medium.

What are parameters and how many are there?

Features of sound waves. Seven.

__________ affects penetration and axial resolution (image quality).

Frequency

What are the typical values of power?

In imaging: 0.004 to 0.090 watts.(4 - 90 milliwatts)

What are the typical values for intensity?

In imaging: 0.01 to 300 W/cm^2

What are the typical values for wavelength?

In imaging: 0.1 to 0.8mm.

Frequencies below 20 Hz are called...?

Infrasonic or infrasound. Humans can't hear it.

Is power adjustable?

Inital power is adjustable yes via the U/S machine.

Is amplitude adjustable?

Initial amplitude is, yes.