...of microwave oven termination signals.

So I was sat in a small room listening to my microwave inform me with a number of beeps that its contents had finished warming. I know that it repeats this warning intermittently. I've sat in that room before, listening. Helpless.
I know that it eventually gives up. Its standard "I'm ready" signal is three monotone beeps. I now know that it repeats these every 40 or 45 seconds, because I just counted it and it came to 42. 'They're surely not going to choose 42 seconds as the repeat interval...it's just not human to do so. I'll come back to 'they' in a bit...it's pretty much 'they' that this is about. After a number of repeated "I'm ready"s - ten, I think, at a guess - it stops. When it stops, the last signal is not an "I'm ready" but a dismissive "Pfft" - a double beep. Now, for a series of beeps, this is very expressive. I actually feel like I've aggravated my microwave. I call it mine, but surely a microwave that can get aggravated is its own person...thing.
So in a factory somewhere - to be honest, I'm picturing Japan - a person or collection of persons ('they') decided the nature of the "I'm ready" signal, the interval between repetitions, the number of repetitions, and the final "Pfft" signal. They surely decided to make it expressive. I don't imagine that they meant to make me feel guilty, but the patience of the repetition and the shortness of the final "Pfft"...it's almost motherly.

"Fine...let it go cold then. You can do it yourself next time!"

So a 'they' or some 'thems' decided this. The microwave didn't. It was a human choice, unless they like...let a monkey roll some dice - I'm still, to be honest, picturing a Japanese fellow in a white coat handing dice to a monkey.
For clarification, the monkey also has a perfectly tailored ickle monkey white coat with ickle monkey biros in the breast pocket.
So I was thinking all this, sat in a small room, thinking how unusual it is that I go to a friend's house...or even an enemy's house...or a neutral house, for that matter...and see the same microwave oven there. There are loads of them. I'm guessing that the manufacturer of my microwave has a range of microwave ovens. I know that manufacturer is not the only manufacturer. I know I don't have only one friend, one enemy or one neutral person to visit. Start multiplying all that together and there are a veritable cornucopia of microwave ovens out there. I know from experience that some go "Ting!", some go "Beep!" and, well...I think it's probably just those in various patterns of repetition. Since I know they don't all beep three times, ten times in a row with a 40/42/45 second iteration period and with an exasperated two beep "Pfft" terminator, we can surely assume that the history of microwave ovens has been witness to myriad meetings of 'themses' deciding on the most expressive "I'm ready" combination. That's got to represent a vast amount of time in the history of human endeavour.
Consider that.

....then consider telephone ring tones.