Immediate Fix
The most common reason for the Slack mobile app having no sound is a conflict between system-level notification settings and app-specific overrides. Often, the app is set to “Deliver Quietly” or the device is in a Focus mode that suppresses audio alerts.
Check Sound and Haptics Settings
First, ensure your physical mute switch is off and your volume is turned up. On Android and iOS, navigate to the system settings and verify that “Do Not Disturb” or “Focus Mode” is disabled. These modes frequently block Slack audio even if the app volume is at maximum.
Verify In-App Notification Sounds
Open the Slack app and tap your profile picture. Go to Settings > Notifications. Ensure that “Allow Notifications” is enabled and that the “Sound” toggle is switched on. If you have custom sounds set for specific channels, verify they are not set to “None”.
| Issue Type | Primary Solution | Success Rate |
|---|---|---|
| System Mute | Check physical silent switch/toggle | 95% |
| Focus Mode | Disable Do Not Disturb | 80% |
| App Permissions | Enable “Sound” in OS settings | 70% |
Technical Explanation
At a technical level, Slack relies on the mobile operating system’s notification daemon (APNs for iOS or FCM for Android). If the audio payload within the push notification is malformed or blocked by the OS power-saving features, the sound will fail to trigger.
When Slack is running in the background, the OS manages its resource allocation. If the app’s cache becomes bloated, the listener for incoming audio pings may lag or fail entirely. Resetting the app’s internal state can force the OS to re-register the audio channel.
# Technical Simulation: Resetting Notification Listeners
$ slack-cli notifications --reset-audio-daemon
$ service slack-mobile restart --clear-cache
Alternative Methods
If basic settings don’t resolve the issue, try clearing the Slack app cache. In the app, go to Settings > Advanced > Reset Cache. This removes temporary files that might be corrupting the audio playback sequence without deleting your message history.
Another common culprit is connected Bluetooth devices. Your phone may be routing the Slack alert sound to a pair of headphones or a car stereo that is not currently in use. Turn off Bluetooth temporarily to see if the sound returns to the phone’s internal speakers.
Finally, ensure your Slack app is updated to the latest version. Developers frequently release patches for audio driver compatibility, especially after a major iOS or Android system update. If all else fails, a clean reinstallation will force the OS to re-prompt for all necessary audio permissions.