As a gulf coast region resident, I can attest to this phenomenon. When the cold front came through this weekend, it was like someone just turned down the volume outside. The difference is incredible, but you can never quite put your finger on any particular source. I do think it's just everyone's HVAC compressors & fans combining into this noise soup. Everyone says they can sleep better when it's colder at night, but I think it's just because it's so much quieter at night around here when its below 70F. The noise floor had to have dropped by 6dB or better overnight.
