Why the person at back on a two wheeler feels hard to listen to sound of the person riding

Situation

Today while I was riding a two wheeler(activa) and was talking simultaneously my sister behind me complaint that she wasn’t able to hear anything I was saying

but I dont get it when we are in a closed space like car there is no problem with sound but when we ride a bike or a cycle the person at back finds it difficult to hear what the person in front is saying

---

I believe the observation should be based on

1. Compression and rarefractions
2. Doppler effect as both source and observer are moving
3. Based on one comment I believe that since I am speaking in direction opposite to that of air, is it possible that there is super position of waves in different phase resulting in a decrease in amplitude

Is there a more logical explanation