The reasons are as follows:
1. If there are obstacles or a long distance between your phone and earbuds, it will cause the other person to hear low sound and noise. Please make sure there are no obstacles between your phone and earbuds, such as taking your phone out of your pants pocket and placing it in your shirt pocket;
2. If the signal at your call location is weak and the network is unstable, it will affect the call quality. Please move to an area with a good signal before making the call;
3. If there is an object with significant electromagnetic interference next to you, it will cause the other party to hear a low volume and noise. It is recommended that you stay away from objects with significant electromagnetic interference such as microwave ovens during use.