[Mpickering1]

I am trying to figure out the formula for this question
I know that 330 m/s is the medium for sound travel in air. I also know that the caluclation d=ct is used but that is where I get confused. The distance of travel is 80 meters long one way so you have to figure 160 meters there and back. Can you help please.

Last week I used a stopwatch to measure the echo time of my snare drum in the hall outside my classroom, which is 80 meters long. The average echo time was 10 milliseconds. Use your understanding of the Echo Ranging formula to prove or disprove my findings, remember this echo was heard in air.


Thanks so much for your help

[Capuchin]

Put 10ms in for t, and 180m in for d, and you should get 330m/s out for c

[Mpickering1]

I think I may have confused you about the question, sorry I added to many variables before I asked the actual question. The question is this

Last week I used a stopwatch to measure the echo time of my snare drum in the hall outside my classroom, which is 80 meters long. The average echo time was 10 milliseconds. Use your understanding of the Echo Ranging formula to prove or disprove my findings, remember this echo was heard in air.

I gave the teacher this equation and she said don't forget that it is 80 meters one way and she said don't forget to convert the m/s to m/ms

D=ct
D=80(10 milliseconds)
Sound travels at a medium of 330m/sec in air therefore the formula would be

T= 80m = 0.24 sec or 240 milliseconds or
330 m/s

The information given above is not an accurate calculation as the medium for sound travel is 330m/sec it is not possible for sound to travel 80m in 10 milliseconds.


Thank you so much for your immediate response.

[Capuchin]

Yes, it is impossible, sound travels about 3.3m in 10ms in air.

I'm still very confused about your question.

How did you measure 10 ms? That's faster than most people's reflexes

[Mpickering1]

I know I have confused you but in a way you helped. Sorry. Ok so I will just give you the question my teacher gave us and see what you think. I will not add any extra comments in there. Below is the question we have in our assignment.

Last week I used a stopwatch to measure the echo time of my snare drum in the hall outside my classroom, which is 80 meters long. The average echo time was 10 milliseconds. Use your understanding of the Echo Ranging formula to prove or disprove my findings, remember this echo was heard in air.

[Capuchin]

Oh okay. What is the "echo ranging formula" or does she just mean distance = speed*time?

so you can rearrange for t --> t = distance/speed

so your figures are 160/330 which is about 0.5 seconds (500 ms) (actually comes out to 485ms)

I see that you have worked out that 240ms is the time it would take, you used 80m which is half the distance.

The value of 485ms obviously disproves your teacher's reading, I would question her scientific method if she actually did the experiment ;)

A 10ms echo would be very hard to hear, you wouldn't really be able to discern the echo from the original sound, 10ms is a very short amount of time. Thus I was confused because the values are not something that would happen in real life.

Hope this helps!