'Weird sounds in the sky' reports have increased in recent weeks and the phenomenon is reflected in the record of google searches here -
Google Trends: strange sounds
This video provides a sample of the sky sounds reported.
Some people don't hear them. That doesn't mean they aren't being heard by others. We all know that there is a gadget called a 'mosquito' which is only audible to persons under 25.
If you hear anything, please mention it here.