sound
hum
dsp
2026-05-26
Lately I have been doing some signal processing to identify humming noises located in my home and local area. Since new year I have noticed humming getting more and more noticeable in my home and local area. This is the second time I am experiencing humming noise.
The first time the humming noise originated from an old electric breaker. The breaker was mounted in the stairwell and the humming noise was able to travel through the walls into the bedroom. It should have been obvious, but it took 2 months before it was found after multiple investigations of the ventilation system. If you experience humming, then please check your electric breakers.
Second time the humming noise are more subtle and more difficult to pinpoint. One of the reason for this is the low-frequency quality of the humming noise below 50Hz. Low frequency humming noise is omnidirectional making it difficult to pinpoint. No obvious direction and can travel far within and outside buildings. I informed the building administrator about the noise and we tried to find the source of the noise.
During 3 appointments we tried the following:
When I had my first experience I create a bunch of Matlab scripts to perform signal processing of the various ventilation and building recordings. This time I have bumped up the scripts and I am working on an Android application making it easier for myself and others to analyze noise and humming.
The images are from the Android app showing different noise spectrums/spectrograms:
A zoomed-in spectrum:
What I can conclude for now:
The first time the humming noise originated from an old electric breaker. The breaker was mounted in the stairwell and the humming noise was able to travel through the walls into the bedroom. It should have been obvious, but it took 2 months before it was found after multiple investigations of the ventilation system. If you experience humming, then please check your electric breakers.
Second time the humming noise are more subtle and more difficult to pinpoint. One of the reason for this is the low-frequency quality of the humming noise below 50Hz. Low frequency humming noise is omnidirectional making it difficult to pinpoint. No obvious direction and can travel far within and outside buildings. I informed the building administrator about the noise and we tried to find the source of the noise.
During 3 appointments we tried the following:
- Turn off all ventilation in the building
- Turn off all elevators in the building
- Turn off all garbage ventilation in the building
- Turn off all garbage ventilation in all building sharing the same garbage collect system
- Turn off the electric breakers in my apartment
- Investigate all basements in the building
When I had my first experience I create a bunch of Matlab scripts to perform signal processing of the various ventilation and building recordings. This time I have bumped up the scripts and I am working on an Android application making it easier for myself and others to analyze noise and humming.
The images are from the Android app showing different noise spectrums/spectrograms:
A zoomed-in spectrum:
What I can conclude for now:
- FFT spectrum show low frequency noise
- Ear plugs does not work for the low frequency humming
- Checked noise level from building transformers
- Recorded during night hours when the city is more quiet
- Biked the local area looking for noise sources, some candidates but no obvious low frequency candidates
- Cars
- Trucks
- Motorway
- Wall drilling
- Elevators
- Dryers
- Washers
- Ventilation
- Airplane
- Heavy industry, I have candidates, but need calibrated microphone
- Local area roof ventilation
- Faulty local area transformers