Say “Hey Siri, turn up the volume”
Use the volume up button on the side of your iPhone or iPad while Siri is speaking
Go to Settings
Tap Siri & Search
Tap Siri Responses
Adjust the Siri voice volume if available
Make sure your device is not in Silent mode
Disconnect Bluetooth headphones or speakers if audio is routed there
Increase the media volume in Control Center
Check that Reduce Loud Sounds is turned off in Settings
Restart your device if Siri volume still seems low