If you do not hear sound from your iPhone, first make sure that the device is not in silent mode, the volume button is fully on, and Bluetooth is turned off. If you still can't hear the sound or there is distorted sound coming in, open any app containing music and adjust the volume using the slider or volume button.
You can also restart your device, because restarting solves many phone issues. If nothing works, the problem might be with the hardware. The iPhone speaker needs to be replaced or repaired.
