constant motor type sounds in the house
According to user LCD, from How do I find out the cause of a low frequency hum in my house?, you can detect the source of the hum with a variety of methods:


  
  Check that others can hear the noise. Other family members, neighbors, etc.
  Make a cone listening device with something like a sheet of paper that you can hold up to your ear. This will help you to better narrow down the location that the sound is coming from.
  Use a stethoscope (you can find one pretty cheap at a drugstore), preferably with a metal head. Use this to try to further locate the source of the sound. Place the stethescope on pipes, walls, floors, radiators, vents, etc. Be careful not to come into contact with electricity as you're doing this.
  Turn off circuit breakers (individual, or the master). If the master breaker stops the hum, then use the individual breakers, one-by-one until the hum returns. If you find the circuit that the hum is on, start tracing that circuit.
  Turn off water supply (individual, or the master).
  


You might also consider using an app on your phone meant for monitoring audio or showing "spectrograms". This might help you to visualize the frequency of the hum.

The above listed reference also includes a variety of potential sources that are worth checking to help identify the potential source.