I thought it was from my windshield too. Taped it off and it was still there. It was driving me nuts. I hate whistles. My 02 Tacoma had a whistle. The dealership replaced the windshield thinking that was where it was coming from. Still had the whistle. They then taped the whole front end, every open space it had. Drove down the road, stoping and pulling off one piece of tape at a time until the whistle showed itself. They found it and it was behind the turn signals. They put some foam tape behind them and I never heard it again. Then I get this 2013 model and I'll be danged if it didn't have a whistle. This time though Toyota already had a TSB on it. It was a 20 minute fix. They did have to order the "parts" to fix it however.