I've got an 03 touring 350Z with 93k miles on it. If I take it above 70mph, I get a sound like this
If I take it back down below 70, the sound goes away.

Any idea what it is? It sounds like it's coming from the rear, but I'm not entirely sure.

 

I really could not hear the sound from your recording.
Does the sound stay there above 70mph or does it go away say,when you hit
80?Could be a wheel bearing.However,my guess its coming from one of your rear
tires.Whats the condition/brand of your tires?Stock?Aftermarket wheel etc?
Its natural for the inside of the rear tires to wear due to the camber.The more
they wear,you will get more of a "whine" especially of smooth black top.

 

I coouldnt hear it either....

 

You can hear it from 11 seconds onwards in the video. I wish I had better audio, but that's the best I could do unfortunately.

The tires are Falken and in good condition, the rims are stock.

I have a feeling that my left rear suspension is bad, although I'm not sure if that would cause the issue.