I did some more testing.
1. One of the questions was addressing that the microphone may be moving inside the chassis. With the windshield vibrating, it could be adding to the sound in a bad way. So, while it was running and there was road noise, I removed the unit and held it by the mount for a short time. In short, there was no difference.
2. I was curious to see what the audio profile was. So I simultaneously recorded a couple of clips with both my mobile phone camera and the DVR. The phone was placed right next to the DVR to get any additional audio reflections from the hard surface of the windshield. I took these video samples and stripped the audio out (and converted to .wav 48kHz stereo). I then viewed the waveform side by side in Audactiy. I did try to keep them the same scale, but there is some difference.
My results:
The first is with the car running, stopped, and very little ambient noise. You'll see 4 big sound pulses. This is my voice saying "Mark Mark Mark Mark" to try and line up the waveforms for analysis. On the right is my phone, on the left is the DVR.
Some observations:
1) The noise floor of the DVR is significantly higher.
2) The peaks are clipped earlier.
3) A lot of the extra detail is lost, although perfect audio fidelity is not required for this type of device. In other words, the lower dynamic range is fine.
4) So overall, the shape is there, but it quickly gets distorted.
5) Just listening to the audio though, I find nothing wrong with either. Both produce usable sound.
This second clip was performed the same way, but instead at 60mph (110kph) on the highway. My car isn't exactly the quietest, but it's far from loud. Windows were shut, no radio was on.
1) The mobile phone on the right, you can see that the ambient noise has significantly increased, which reflects real world sound.
2) You can clearly see the four pulses again on the right, although they are starting to get distorted. Again, the phone audio is usable.
3) The audio from the DVR, to be frank, is totally misleading. I couldn't find my 4 pulses at all. The entire waveform is saturated by ambient noise and there's no detail in the sound left. Additionally, there's significant clipping everywhere.
As suspected, it appears there is just too much audio gain in the unit. It needs to be lowered significantly.
. The audio was perfect with no distortion at all, although this isn't a true test as to in the vehicle but I think maybe it's at start. I don't have the time right now to rig up a power supply for my truck so this will have to wait until this evening, but I do have some confidence. Also so maybe this why some people are having trouble with the imagine that the camera produces, it may be as simple as having to high of voltage. I will post here as soon as I have tested it with the correct voltage in the truck. Good Luck to all.
