After listening to your sound, and glancing at the Venturi Mini web site, I'm convinced that the sound is not a ground loop.

In order to have a ground loop, you need physical electrical connectivity between more than one device, each with its own power supply.

If I'm reading the web site correctly, the Venturi Mini is not physically connected to your stereo, nor is it physically connected to your phone. It works entirely with Bluetooth (input) and FM radio frequencies (output). So it can't be a ground loop.

I believe your problem is simple FM radio interference. Every solution I've seen that uses an FM transmitter to play music into your car stereo is complete crap, and is always beset by exactly these kinds of noise problems.

It could very well be the Android itself generating the interference, or any number of other things in the car. Does the Venturi Mini have an option to change which FM band it broadcasts on? If so, it might be worth experimenting with. You can also try re-orienting the location of the Venturi Mini, or the phone, in the cabin of the car and seeing if either of those alter the characteristics of the noise. (To alter the positon of the Venturi, you'd either need a cigarette lighter extension cable (I've actually seen these), or some other kind of 12v connection, or another cigarette lighter location in your car.)