Wind turbine loudness

I stood this close to the turbine and used the dB meter. 

60dB is like the gale through the poplar tree. I wondered if the time interval for the large scale oscillations matched the turbine's rotations. 10 turns in 20 secs means time period is 2 secs. It doesn't match. 

Headphone volume

There was an article in The i on Monday about an epidemic of tinnitus. It links it to prolonged headphone use at high volume. Over 85dB for long periods is bad. It suggests using maybe 60% of full volume on your device to avoid this. I tried my dB app on my headphones. Not sure how good the reading is but it is mostly in the 60s.

Fight gravity!

I loved this car sticker. In a sense, just standing up is fighting gravity. I suppose it means "doing work against gravity" and that is how I have gravitational potential energy. 

Weighing the length

I've been knitting hearts that can be filled with stuffing. I don't have much wool left and was wondering if I had enough wool to knit the two halves. I normally measure length but I don't know how long a section I need.

I'm a bit late to the party on this one but I realised I should weigh it instead. I used the empty tub to get over the low mass cut off - it won't read below 10grams though after that the resolution is 1gram.

And there is enough for the two halves. So an odd bit of metrology.

Magnet recycling

There is a good piece in this month's Physics World about the recycling of rare-earth magnets, citing their roles in wind turbines and electric car batteries. It states that 259 million hard disk drives for computers were shipped in 2021. They tend to go to the tip every few years as a new computer is needed. I have extracted several of the magnets to play with. Previously long-loop recycling was used and the whole thing was broken down, the rare earths being recovered as oxides. Energy is then needed to convert the oxides back into metals before casting alloys, reducing this to powder and then turning the powder into metals. Under a new short-loop process the rare-earth alloys break apart to form a powder after treatment with hydrogen. Much less energy is needed so if it scales up well, this process is probably the future!

How loud is the storm?

I've posted about the sound spectrum of the wind in this big tree but now I've got a dB meter. We were sat in the greenhouse sheltering from the wind and Storm Kathleen was raging. Peak volume from the tree was over 80dB. Some sources have that as being "busy traffic", which seems about right.

There were quiet lulls as well. Interesting to note that these lasted about 5 seconds.

Energy in petrol

This wrecked exhaust silencer shows the energy in even a small amount of petrol. An Internet search reveals varied answers but one gallon of petrol contains the same energy as over 10 sticks of dynamite. This has led me to find more information on the energy density of fuels. This site gives diesel as containing more energy per litre than gasoline whereas this one has them about the same for energy per kilogram. This is because petrol is a little less dense than diesel. That said, it is litres that I put into the tank, not kg. I was also interested in the Gasoline Gallon Equivalent.