Interesting seeing all these comments being raised about the veritable mainstay of British industry, the Weller like this and its associated transformer buzz. My old Katsu, a 936D clone also suffered from that buzzing as well and working late at night like I tend to do, I was very conscious of it. My new solder iron is silent, well apart from its buzzer that it is, but you can turn it off if you want to, depending on the user settings you select.
It just signals when its going into sleep mode and power off modes and also when you pick the iron up it squeaks to alert you that it is activated otherwise it as quiet as a church mouse.
If ever I want to be transported back a few years I have around the place and in the garage about half a dozen of the old direct mains heated irons and at least one with a temp control in the handle, about as much as chocolate fire guard, it was either on or off and was in a part of the handle where it was always getting knocked so it was getting adjusted accidentally in use, bloody useless heap it was and that's what lead me to get the 936D clone which was fine until the tips and the heater began to oxidise on the inside then it became unpredictable but still far better then what I had before.
![Popcorn :popcorn:](https://www.eevblog.com/forum/Smileys/default/EatingPopcorn.jpg)