Hi there! I understand you're having trouble with sound on the BBC World Service app. Let's troubleshoot this together.

1. Check Volume Settings: First, make sure the volume on your device is turned up and not muted. Sometimes, the simplest things get missed.

2. Restart the App: Close the BBC World Service app completely and then reopen it. This can often resolve temporary issues.

3. Restart Your Device: Try restarting your computer. This can refresh your system and fix minor glitches.

4. Check for Updates: Make sure that both the BBC World Service app and your operating system are up to date. Sometimes bugs are fixed in newer versions. You can check for updates in the Windows Update settings.

5. Network Connection: A stable internet connection is essential for streaming audio. Ensure you are connected to the internet and try switching it off and back on again.

6. Audio Device Settings: Go to your device's sound settings and ensure that the correct audio output device is selected (like speakers or headphones).

If you've tried these steps and the app still doesn't produce sound, please let me know, and we can explore some more advanced troubleshooting steps! Are you satisfied with this initial guidance?