Calculate the diameter of a baby's head using ultrasound speed

In summary, the baby's head can be calculated to be 8.6 cm in diameter using ultrasound and a time delay of 96 μs.
  • #1
Littlegirloud
6
0

Homework Statement


Calculate the diameter of a baby's head if there is a time delay of 96 microseconds between receiving pluses from either side of the skull and the speed of ultrasound can be assumed to be 1250m/s.

Homework Equations

The Attempt at a Solution



The diameter of the baby’s head can be calculated using distance = speed x time where:

Speed of ultrasound = 1250 m/s
= 0.00125 m/ms

Therefore:
Distance (diameter) = 0.00125 x 96
=0.08625 m
= 8.6 cm (1dp)

Where am in going wrong? I'm advised to think about the echo factor the sound waves leaves the transducer reaches the skull and then has to travel back to the transducer.

Please help!
 
Physics news on Phys.org
  • #2
Littlegirloud said:
Distance (diameter) = 0.00125 x 96
=0.08625 m
I get a different result in that multiplication.

There is another error. Imagine the source of the sound is directly at one side of the head of the baby. In terms of "head diameters", how far does the sound travel to reach the opposite side of the head and come back?
 
  • #3
Thanks for the pointer on the calculation, I'll do it again. Is the second mistake that I'm only considering travel time in one direction? So 96x2 to a count for return time too? For some reason I'm just really struggling to get my head around (pun half intended) this one.
 
  • #4
Littlegirloud said:
So 96x2 to a count for return time too?
That is the wrong direction.
The sound needs 96 microseconds for both directions together.
 
  • #5
Thank you!
 
  • #6
Here's my updated attempt. Closer?

The diameter of the baby’s head can be calculated using distance = speed x time where:
Speed of ultrasound = 1250 m/s
= 0.00125 m/ms

and if 96 microseconds is the time taken for the wave to reflect then time taken across the baby’s head = 96/2
= 48

Therefore:
Distance (diameter) = 0.00125 x 48
= 0.06 m
= 6 cm
 
  • #7
Littlegirloud said:
Here's my updated attempt. Closer?

The diameter of the baby’s head can be calculated using distance = speed x time where:
Speed of ultrasound = 1250 m/s
= 0.00125 m/ms

and if 96 microseconds is the time taken for the wave to reflect then time taken across the baby’s head = 96/2
= 48

Therefore:
Distance (diameter) = 0.00125 x 48
= 0.06 m
= 6 cm
Yes, but "ms" is the abbreviation for milliseconds. For microseconds it is μs.
 

Related to Calculate the diameter of a baby's head using ultrasound speed

What is the formula for calculating the diameter of a baby's head using ultrasound speed?

The formula for calculating the diameter of a baby's head using ultrasound speed is: diameter = speed of sound x time / 2.

How do you determine the speed of sound in the calculation?

The speed of sound used in the calculation is typically set at 1540 meters per second, which is the average speed of sound in human tissue.

What is the role of time in this calculation?

Time is a crucial factor in calculating the diameter of a baby's head using ultrasound speed. The time is measured from the moment the ultrasound wave is emitted to the moment it is received after bouncing off the baby's head.

Can this calculation accurately determine the diameter of a baby's head?

Yes, this calculation is a reliable way to measure the diameter of a baby's head. It is commonly used in medical settings and has been proven to be accurate.

Are there any limitations to this calculation?

While this calculation is a useful tool, it does have some limitations. It may be less accurate in cases where there is an abnormal shape or size of the baby's head, or if there is excess fluid in the mother's uterus.

Similar threads

  • New Member Introductions
Replies
1
Views
49
  • Introductory Physics Homework Help
Replies
7
Views
2K
  • Introductory Physics Homework Help
Replies
3
Views
5K
  • Introductory Physics Homework Help
Replies
2
Views
4K
  • Introductory Physics Homework Help
Replies
3
Views
978
  • Introductory Physics Homework Help
Replies
33
Views
3K
Replies
3
Views
6K
  • Introductory Physics Homework Help
Replies
12
Views
3K
  • Introductory Physics Homework Help
Replies
9
Views
6K
  • Introductory Physics Homework Help
Replies
5
Views
6K
Back
Top