# problem with the dopper effect (1 Viewer)

#### red802

##### Member
-describe the Doppler effect in sound waves and how it is used in ultrasonics to obtain flow characteristics of blood moving through the heart

-outline some cardiac problems that can be detected through the use of the Doppler effect

can someone explain this in easy terms, and please dont link it to hsc online

#### Mountain.Dew

##### Magician, and Lawyer.
my physics is rusty after about 1/2 yr, so please bear with me...

-describe the Doppler effect in sound waves and how it is used in ultrasonics to obtain flow characteristics of blood moving through the heart

the Doppler Effect is the effect of the apparent change in wavelength or frequency of sound waves from a source as that source moves uniformally relative to a stationary observer.

how it is used in ultrasonics: projected ultrasound waves are reflected off moving red blood cells that 'changes' the wavelength or frequency of that original ultrasound. this new wavelength is recieved and compared with the original wavelength. the discrepancies calculate the value of red blood cell's velocity at that point. obtaining multiple velocities would help us to obtain blood flow characteristics.

-outline some cardiac problems that can be detected through the use of the Doppler effect

usually heart disease - pretty much any other cardiovascular disease that involves the impedenece of the flow of blood (e.g. can analyse if there are blood clots, perhaps other abnormal blood flow, etc...

hope this helps, M.D.

#### beemz

##### New Member
Re: problem with the dopper effect II

doppler effect....
without linking it to ultrasound etc. exactly
just describing it
if the source is moving, waves infront bunch up; increasing frequency blah blah and waves behind spread out and opposite happens...
in diagrams i have seen the wavelengths of all infront are the same size, should they not be getting smaller?.. or the ones behind getting bigger as the source moves forward???
:\$
just checking...

#### alcalder

Re: problem with the dopper effect II

beemz said:
if the source is moving, waves infront bunch up; increasing frequency blah blah and waves behind spread out and opposite happens...
in diagrams i have seen the wavelengths of all infront are the same size, should they not be getting smaller?.. or the ones behind getting bigger as the source moves forward???
:\$
just checking...
It all depends on whether your body is moving with constant velocity or not. If it is travelling with constant velocity then there wavelengths are constant - bunched up at the front and spread out at the back.

If the body is acclerating then the wave lengths at the front will be bunched up but getting closer and closer together as the body catches up on its previous waves, until it hits the speed of sound and all the wave lengths meet at one point - hence the sonic boom.

The converse for a decelerating body.

Hope that helps

#### Irskin

##### Member
The Doppler Effect is the apparent change in frequency of sound waves when there is relative motion between an observer and a source of sound waves.
A pulse of sound waves is sent through the body in the direction of blood flow from and back to the heart. Any changes in frequency can be detetced and problems identified. For example, if there is not enough blood being pumped out of the heart or if it is not at an efficient reat. It is important to note that the transducer sending the pulse of sound waves must be directed down towards the flow of blood from the heart so that it measures the rate of blood flow of blood leaving the heart.

Many problems (cardiac) can be detected using flow characteristics and Doppler ultrasound. The left ventricle can be analysed to see if it is pumping enough blood around the body, valves can be studied to make sure they are operating correclty and are not blocked by fatty tissue etc...

#### beemz

##### New Member
Re: problem with the dopper effect II

great! thanks alcalder! i think thats what i wanted to know