Trumpet / Clarinet Sound
 

My 07 Veracruz makes a sound like a trumpet or clarinet intermittently at highway speeds. The sound appears to come from behind the radio maybe near the firewall. I have been through many theories, the latest of which is that it is air rushing in or out of somewhere. This is based on it getting worse with headwinds.

Has anyone else experienced this?
Thanks in advance;
-Todd