Find difference in echo times, doppler shift?

[Angie_Agnes]

Homework Statement

A bat is pursuing an insect, and using echolocation of 41 kHz sound waves to track the insect. The insect is initially 34 cm from the bat but then moves to a distance of 44 cm as it tries to escape. What is the difference in the two echo times that the bat measures?

Homework Equations

I'm not sure... is this a doppler shift question? the book has a few sentences about bats using reflection time and doppler effect to judge distances of objects.

This is an equation for radar: Ltot=vΔt
λ=v/f

Doppler shift (moving away from observer)
Fobs=(fsource)/{1+(Vsource/Vsound)}

The Attempt at a Solution

I attempted to find time by using the Ltot=vΔt equation. 2(.34)=343t -> t=.0019s
2(.44)=343t -> t=.0026s. Obviously wrong. Don't know where to start. Please help.

 

[technician]

I don't think it is a doppler effect question. I think it is just two echo times.
You need a value for the speed of sound

 

[Angie_Agnes]

the speed of sound is 343m/s

 

[technician]

Now calculate the time to echo from 34cm, then from 44cm.
The difference??

 

[Angie_Agnes]

had a miscalculation the first time I did it. Thanks.