The “Hum”

The Fairview Cove Container Terminal – Halifax NS

This story goes back at least 45 years! When I lived on Braeside Lane in the late 70s I found myself experiencing a definitely audible “hum”, particularly in the middle of the night, which drove me crazy. It sounded like a very large diesel truck idling just outside my building.

A low frequency hum, almost a vibration, just on the threshold of human hearing. It’s not particularly loud. In fact, you might not have even noticed it yet – but once you do, you can’t stop hearing it. It sounds like a truck, idling on the street in front your house. Or the atmospheric din of an airplane flying overhead, that never gets further away. You can hear it when you’re outside, but it seems louder indoors, and particularly at night, when you’re lying in bed. Maybe it keeps you awake.

If you do hear it, you’re among the roughly 4% of the world’s population affected by “the Hum”, a frequently reported but little understood global phenomenon.

[From The Guardian – July 7 2021]

I struggled with the “hum” for a couple of years before finally I had the brilliant idea to call the acoustic engineers at TUNS (Dal) to see if they were aware of the “hum” and what they knew about it. Not much, it turned out, but they were interested.

Two guys came to my house with some fancy recording equipment for me to use after, say, 2:00am to see if I could capture the noise that for me was so audible and irritating. I recorded the “hum” for a week, after which they came back, collected the microphone and recorder, and analyzed the recordings.

Then they reported back to me. They could definitely detect a low pitch noise (somewhere around 40Hz – they were actually more specific but it’s been so long ago I can’t actually remember the precise number) around 5-10 decibels – loud enough for some people to hear even at that low pitch. They had no idea what the source of the sound was but they assured me it was real.

My Braeside Lane townhouse was constructed on bedrock – a continuation of the Halifax bedrock on which the Fairview Cove Container Terminal was built – so it was not inconceivable that the vibration made by the large cranes or the idling container ships docked at the port, particularly at night, might be transmitting a sound through the bedrock and reaching my house.

No way to prove that theory but I took comfort in knowing the “hum” was a real sound.

I was fortunate, in that I discovered a “node” of that vibration that happened to occur at the foot of my bed, about the diameter of a 15″ platter. Well, that helped a lot – a silent spot in the middle of the thrumming low pitch vibration was a godsend – I was able to sleep comfortably with my head at the foot of my bed and be oblivious to the “hum.” (Although it took some time to feel comfortable/safe sleeping with my head in the middle of the room!)

When I moved to Winnipeg a number of years later, and was looking for a place to live, the first thing on my list of things to watch out for was any “hum”! The realtor and I would visit a place during the day. I’d ask for silence as I walked through the house or apartment trying to listen for any “hum” particularly in the bedrooms. I wasn’t surprised to encounter a variety of “hums” – refrigerators, air conditioners, traffic, railway lines – a city is full of “hums”. I was trying to listen for that unidentified low pitch “hum” I wanted to avoid. I drove the realtor crazy asking to return to a location late in the evening so I could listen to the ambient sound before I’d consider purchasing. I finally found a condo on the Assiniboine River that fit the bill – I was never bothered by the “hum” during the four years I lived there.

When I returned to Halifax in 1997, same thing. House hunting, making sure I wasn’t also buying a “hum” to go along with the house. Again I was lucky. My Chelsea Lane townhouse, although built on the same bedrock as Braeside Lane was further from the container terminal, and “hum” free. I wasn’t bothered by any “hum” for the 20 or so years I lived in it (there was a large CBC radio antenna not far from my place, but I never encountered a “hum” emanating from it).

In August 2016 I moved into an apartment building, 6th floor (top floor), checked for “hums” – thought I’d managed to escape once again. However, on Oct 19, two and a half months later, as I was returning to bed from a trip to the bathroom at 3 in the morning, I was assaulted by a very pronounced “hum” – it persisted for the rest of the night and into the next day. I could hear it – I could feel it thrumming in my head. I could block it out if I turned on the radio, which I did. It wasn’t the highway traffic on the other side of the building – that was intermittent, and besides I really didn’t hear the vehicles, even when standing on my balcony. It might have been the air circulating fans on the roof close to my apartment – but then why hadn’t I heard them when I checked before moving in?

The “hum” was everywhere in the apartment, I could not find a silent node anywhere. I tried identifying the pitch of the “hum” using the keyboard on my iPad. It seemed to blend as a harmonic with F/F#/G two octaves below middle C – I’d lose the “hum” when I played those notes, although I couldn’t pin it down precisely (C1 – three octaves below middle C has a frequency of 32.70 Hz – which is close to the acoustic range mentioned in the Guardian article; it’s also a harmonic with F so it’s possible the base pitch of the “hum” is somewhere around C1 with harmonics further up the scale).

The “hum” never quite subsided, but I discovered an App for my iPad – White Noise – which produced a range of backgrounds to block offending noises. The sound which worked best for me, believe it or not, was the ambient sound of the International Space Station! That, combined with “grey noise” which I was able to pitch closer to F2/F#2/G2 worked to mask the “hum” – so just before turning out the light, I’d turn on White Noise and run it for the night. It allowed me to fall asleep. I used the App nightly for a couple of years and then the “hum” seemed to disappear. I stopped turning on White Noise before getting into bed.

The “hum” returned last evening! At 9:40pm – there it was again – that loud low pitched thrumming – I actually went outside to see if I could see a large diesel truck idling nearby – nope, no vehicles anywhere near the front of the building. Even turning up the volume on the TV couldn’t block the “hum”. I was getting ready to turn on White Noise when around midnight the “hum” subsided. I went to bed and was able to fall asleep.

However, this morning, it was present still, although at a lower level. I can ignore the “hum” during the day – I keep the radio on, listening to CBC or some podcast or other. It generally doesn’t bother me too much in the evening, either, the volume of the TV (to which I knit) generally masks it. And I have discovered that the programs delivered by Brian Cox (professor of particle physics in the School of Physics and Astronomy at the University of Manchester) put me to sleep quite quickly! As does David Attenborough. I’ve recorded a collection of programs by both men, which I set to play for a half hour, to mask any disturbing “hums” which might interfere with me falling asleep.

I’m waiting to see if the “hum” is present again this evening! It was very loud and irritating last night. I have found ways to mask it, making living with it bearable.

I just wish the “hum” would simply go away!