This question already has an answer here:
We hear/feel a pulsating sound/vibration in our house and in our car (when the car is parked at the house. The sound cannot be heard outside. It continues even after the circuit breakers are turned off so we believe the source is external to the house. We would like to measure and characterize it to help us determine the source. There are a plethora of devices out there. How should we select a high quality, but not excessively expensive - if possible - device?