Electrical Hum in Apartment Building

[HubriSonics]

There is an electrical hum in my apartment building.

REW’s real-time analyzer indicates that the loudest components of the hum are at 30 Hz, 60 Hz, 120 Hz, and 180 Hz. The SPL of individual peaks often reaches 55 dB.

Var smoothing reveals comb filtering that is not revealed at 1/48 octave smoothing.

Does anyone know what might be causing this noise?

 

[sam_adams]

Motors from HVAC systems, refrigerators, elevators. Mutli-unit buildings are always abuzz with low frequency vibrations. Interesting to note that the peak at about 60Hz looks to be actually 59 Hz. I've seen the same type of backgound noise.

 

[HubriSonics]

I have a friend who thinks it is unlikely that the hum would have a component at 59 Hz, but that it is likely that the hum would have a component at 60 Hz. My friend thinks that REW is misreading a 60 Hz component as being at 59 Hz.

In my opinion, modern digital power supplies can behave strangely, and perhaps the frequency of the AC power is being changed by the power supplies for the cell phone antennas on the roof of my apartment building.