there must be an alarm somewhere within your home, maybe an old mobile phone, electricity meter or could it be the smoke alarm? not sure why it should appear like it occurs in different rooms but definitely an alarm, maybe a watch, clock anything like this.
That loud "beep" sound that you have heard once every hour is the device that deteced fire/smoke harzard. However, since it's "beep" every hour, means that the homeowner is required to replace new battery.
