Doppler effect problem (observer is moving away)

[Emmanuelle]

Ben is walking in a park in a straight line at 1.2 m/s. A bird is hiding in a bush. When Ben is closest to the bush, he is 2 m away from the bird and he hears a 10 dB sound. How long will he continue to hear the bird?

Thanks for your help!

 

[NascentOxygen]

Please attend to points 2 and 4 ...
https://www.physicsforums.com/threads/guidelines-for-students-and-helpers.686781/

 

[Dick]

Ben is walking in a park in a straight line at 1.2 m/s. A bird is hiding in a bush. When Ben is closest to the bush, he is 2 m away from the bird and he hears a 10 dB sound. How long will he continue to hear the bird?

Thanks for your help!

This isn't about the doppler effect. A speed of 1.2 m/s won't affect frequency much. It's more about how distance affects sound intensity. There are some assumptions to be made here.