Let me briefly share with you the steps.

Computer: MacBook Air

System: macOS12

Software: WPS (PPT) 2019

1. First, we open ppt and click Speaker button for background music.

2. Then the options pop up and click the volume in the upper left corner.

3. Then we click Mute.

I hope it will be helpful to you. If you have any questions, please leave a message. Thank you.