Our trackers with live audio have a small microphone hole usually on the front face or side of the tracker. This hole needs to be pointed in the direction of the person speaking. If you can place it out in the open, do so.
In our experience, the best hidden location inside a car is underneath the passenger seat. There is usually a metal bar that you can fix the tracker to.
Note: if you put the tracker on the outside of your vehicle you will hear sounds of the road, but not the people inside the car. Thus, the device must be inside the car.
Our devices function first as GPS tracking devices, second as live audio monitors. If you are looking for a device with the best audio quality we recommend the Car Charger Tracker. Out of all of our products, this device has the best audio quality.