TV settings
Make sure the volume is turned up on both the TV and the DVD player. Also, check the audio settings on the TV to ensure that the volume is set to the appropriate level.
DVD player settings
Check the audio settings on the DVD player to make sure that the volume is turned up. Also, make sure that the audio output is set to the correct type of connection (e.g., HDMI, optical, etc.).
Cable connections
Make sure that the cables connecting the DVD player to the TV are properly connected and secure. Also, try replacing the cables with a different set to rule out any cable issues.
Speakers
If you are using external speakers, make sure that they are properly connected and powered. Also, check the volume settings on the speakers to make sure that they are turned up.
Audio format
Some DVDs may be encoded with a different audio format than your TV or DVD player can support. Check the audio specifications on the DVD case to make sure that your equipment is compatible.
If you have tried all of these suggestions and you are still having trouble hearing the sound on your DVD player, you may need to contact the manufacturer of the DVD player or TV for further assistance.