This GPS is designed for motorcycle riding.
Riders are better to use a Bluetooth headset to listen to navigation audios to avoid noise disturbance.
If you use it in a car, sound directly from the GPS is also very low. But there is another way to resolve this problem, pls have a try:
As we know, this GPS supports an FM transmitter. This function is designed/special for use in cars. It’s just an FM launcher that changes navigating audio signal into frequency modulation signal and playing in your car stereo system.
That means you can listen to the GPS’s voice navigation, music, etc through your car stereo speaker with an FM transmitter.