the hum at 86.1Hz.

sunday, january 22nd, 2023.

I stayed up until 2 a.m. last night trying to figure out the cause of a low-pitched hum in our house's crawlspace that started last night. Flipped breakers off and back on, cut the mains power. Nothing would cull the sound. I went to bed with a mystery and an "oh no, did something else break?" feeling.

I probably dreamt of the hum, too.

I woke up this morning and saw that @michal@kottman.xyz recommended using a spectrum analyzer to chase down the problem. I downloaded a smartphone app called FFTWave and recorded the hum as heard from the center of the floor in my front room:

There it is! A steady 55dB hum at 86.1Hz. Not exactly the 60 Hz I'd expect from something electrical.

How strange!

a brief detour about small GIFs.

I wanted to share the .mov I recorded on my phone of FFTWave, but it clocked in at over 4 MB! I was able to reduce it to a much smaller 87 KB .gif using ffmpeg and gifsicle:

$ ffmpeg -i fft.mov -r 30 -s 480x221 -t 00:00:01 fft.gif
$ gifsicle -i fft.gif -O3 --colors 32 -o fft_optimized.gif
$ ls -lh
total 4.4M
-rw-r--r-- 1 chotrin chotrin 4.3M Jan 22 10:36 fft.mov
-rw-r--r-- 1 chotrin chotrin 126K Jan 22 10:54 fft.gif
-rw-r--r-- 1 chotrin chotrin  87K Jan 22 10:55 fft_optimized.gif

back to the investigation.

It's a bit dreary and wet outside today, so I didn't expect I'd be crawling around under my house to investigate. But I did wander around outside, FFTWave in hand. I noticed that my outside water spigot was vibrating— I felt it rattling in my hands! So I grabbed my wrench to cut off the water at the meter.

Sure enough, the whole water main is vibrating. You could hear the hum outside! I walked down the street to the end of the road, probably looking a little looney in my slippers and holding a wrench. The entire neighborhood was quiet except for bird chirps and that 86.1Hz hum!

I turned around to head back to my house and noticed my neighbor sitting in his carport looking quizzically at me. I introduced myself and shared the story about my plumbing vibrating and the hum and he replied, "you hear it too?!?"

He also mentioned that some neighbors across another street had their water go out yesterday. I spoke with my partner about this and they recollected seeing a fire hydrant gushing and gushing yesterday afternoon a few blocks away. Perhaps we're getting closer to the source.

I called the city utility's emergency telephone number and reported what's going on. They indicated they had a water main that was repaired yesterday. She took my name, number, and address and said they'd send someone out to investigate.

to be continued?

I haven't heard back from the city and the hum continues. Hopefully they'll get it sorted soon enough and let me know what happened! I'll be sure to share it here if I do, but I don't really expect they'll call me back.

For now, it's time to finish my coffee and have a bit of lunch. What a strange day I've had so far!

Until next time, be well! :)