I have a 2004 Monaco 34 ft. It is a diesel pusher. Purchased in May of 2017. At purchase it had 29,000 miles - was kept in a garage by the original owner. When I purchased it I had a local mechani...
Check door seals, Window seals and espically around the windshield.. If the glass has MOVED (yes it can) you may have a small gap and what you hear is a "Whistle" thus produced.. But without hearing the noise with my own ears.. I can not be sure.
Next step... Using your phone's VOICE RECORDER.. Record and upload an MP3. Perhaps someone (not necessarly myself) can identify the specific sound.