Medical Physcis CH 5 Waves& Sound

Mechanical waves are waves that require a …………..

medium

A medium is a form of ……………through which the wave travels such as

matter (water, air, glass)

Waves such as light, X-rays and other forms of radiation do not require a ………….

medium

Transverse wave is a type of …………. waves that moves…….

Mechanical wave that moves up and down a right angle to the direction of the wave

Types of Mechanical waves are

Transverse, Longitudinal (compression waves)

In longitudinal waves the matter in the wave moves……….

back and forth parallel to the direction of the wave

The tuning fork ………. and you hear a sound

vibrates

sounds are made when an object

vibrates

Sound is a ………that ………………………… in a medium

longitudinal wave, that propagates via pressure variations

pressure waves vibration produces areas of …………. and changes are recorded by the ear ……….

higher pressure , drum

Place a ringing clock inside bell jar and what happens?

There is air inside the jar so sound can travel and be heard

Remove air from bell jar and what happens?

The sound cannot be heard because there is no air inside (vacuum)

Required elements of sound

1- Source of vibration 2- energy 3- path or medium 4- receiver

Speed of sound is dependent on……………..and………, and doesn’t depend on the frequency of the wave

the medium and the temperature

Speed of sound can roughly be considered as a constant=…………

1540m/s in the human body

Speed of sound equation

Speed of sound is constant for …… and is determined by ……and……..

any medium, by density and compressibility of the medium(measured with bulk modulus of elasticity k)

Incompressible medium has …………velocity

high

Bone is very ………….., has ……… k and higher………….than…..

incompressiblem high k, higher speed of sound than muscle

sound needs substance to travels by

particles vibrating

Sound waves travel fastest through ………..

solids.

in a solid particles are closer together This means vibrations are more easily ………..from particle to particle and so sound travels ………….

passed, faster

The ………..the medium, the faster sound will travel.

denser

type of substance …………the speed of sound

affects

A healthy human ear can hear frequencies in the range of ………………….(sonic).

20 Hz to 20,000 Hz

Humans cannot hear below Hz. Sounds below this frequency are termed infrasonic

20

The higher the temperature, the faster the particles of the medium will move and the ………. sound will travel

faster

Sounds above 20,000 Hz are termed………. dogs can hear them but not humans

ultrasonic

The larger the amplitude of the wave on the trace, the

……….. the sound

louder

which is louder

A

the pitch of a sound is shown by…………

frequency

The greater the number of waves across the oscilloscope trace, the……………the frequency and pitc

higher

Frequency is perceived as pitch; Low freq. =………… High freq.=………………..

Low→bass pitch

High→ treble

Sound intensity is the …………..that the sound

wave possesses

energy

The greater the intensity of sound the ………. the sound will travel and the ………….the sound will appear.

farther, louder

Loudness is a ………..Relative to surrounding and intensity

sensation

Humans can detect intensities

as low as……..

The threshold of pain

is

10-¹² W/m2, 1

intensity formula

Acoustic Impedance (Z ) It is a measure of the ………..of the particles of the medium to mechanical vibrations

resistance

For a plane wave Z is also given by: …..with unit

Kg/m² . s

Bone has a ……….acoustic impedance than fat, since the density of the bone is very high

higher

The most important single interaction process for purposes

of generating an ultrasound image

Reflection

types of reflection

1- Specular reflection

2- Non-specular (diffuser or scattered) reflection

Types of reflection depend on

- Size of the boundary relative to wavelength of the

ultrasound beam.

- Irregularities of the shape on the surface of the reflector

What’s the difference between Wave Reflection Types

-specular

-Medium

-Scattered

specular → large impedance→ large reflection reducing wave amplitude

Medium→ dense tissue(muscle)

Scattered(diffuse)→ soft tissue(liver)

When a sound wave hits the body:

- part of the wave is reflected

- part is transmitted into the

body

in interference The alternating pattern produces a ……………..

beat

If an ultrasound wave meets, at an oblique angle, a boundary

between two media having different speeds of sound, the transmitted wave will be …………

deflected

(ultrasound waves) if the velocities are equal, There would be no …………..occurred

and the beam goes straight into the second medium

refraction

the velocities of the different tissues in the human body are

quite close, refraction's can be ………

ignored

A echoes is a ………..sound wave

reflected

Sonar systems use ………… to map out objects

underwater

sound waves

The amount of time it takes for echoes to return

depends on …………… the reflecting surface is

how far away

……………. – the ability to emit high pitched

squeaks and listen for echoes. Bats and dolphins use it

Echolocation

In ………………. sound is received by chest piece and sent to the earpieces by multiple reflecting through a long tube.

stethoscope,

In doppler, As you move closer to the source you encounter each sound wave a ……………,ex of using doppler effect are……

little earlier, radar for speeding cars

The closer you get the …………the pitch

higher

When you move away , each sound wave takes longer to reach

you, you hear fewer ……………., which results in a …………pitch

wavelength, lower

Clinical Ultrasound – uses……….. sound waves

high frequency