170000 mi-high whistle sound when idle,shift or drive.No codes or warning lights

Thank you. At first they told me it was a barring in the engine...??? then they said it was the alternator. I just had them put in an alternator last October so they had to replace and fix for free but didn't want to give me any type of paperwork.... stating that they just have to send it in as a warranty claim. The noise is gone but I will be paying close attention for a while. Thanks again and that was an impressive guess!