The Law & Order sound is the strangely reverbed clanking thingy that accompanies black title screens on episodes of Law & Order and Law & Order: Special Victims Unit that indicate a sudden scene change. E.g.:
4132 Some Place in New York
[Time — optional]
*Law & Order Sound*
According to IMDB, the noise was created by mashing together about a dozen different sounds, one of which featured a bunch of monks stamping on a floor. This is by far the most interesting fact about the sound, but of course, since it's IMDB, you're never going to find even slightly more explanation than that. For years, fans online referred to the sound as the chung-chung, until the USA network started running promos featuring some of the cast. In them, Dann Florek, who plays Captain Donald Cragen (appearing in the first three seasons of the original show and in every season of SVU), referred to the sound as the doink-doink, and the name's pretty much stuck.
Law & Order is on nearly 24 hours per day, and while it isn't the greatest show by any means, it usually can be relied upon to not suck. Thus it worms its way into fans' lives: the show that's always running as a marathon somewhere, sometime, the show that can always be put on in the background while you iron some clothes, dust, make dinner, tinker with something. In this way, you wind up hearing a lot of doink-doinks. I couldn't sleep one night because my mind simply wouldn't shut down, and I found myself watching — you guessed it — Law & Order reruns because every other option involved trying to sell me something extremely absorbent or a twiggish blonde woman walking through a world filmed in blue and seeing dead people and then putting them to rest by asking inane questions of living people who she'd meet and then magically see them as their past selves. So I started to wonder, how many times have I heard that doink noise during my life?
According to Wikipedia, the original show has aired 433 episodes, while SVU has aired 216. There was a Criminal Intent episode on another channel, so I flipped over to watch it and noticed it didn't use the sound at all. I don't know if that was always the case, but I'll just assume it's not in the show, except for the intro credits. That brings us to 649 total episodes. Now for math.
The show's producers relied on the doink-doink an awful lot more in years past, and it seems to have gotten phased out over recent seasons, but I think a healthy estimate of uses per episode, as a series average, is seven. Which brings us to 4,543 goddamn doink-doinks. At an average duration of five seconds, that's 22,715 seconds, or 378.6 total minutes, or 6.3 hours, or about a quarter of a day.
Now, remember what I said about there always being marathons of the show on and how it could be relied upon to not suck? Well, factor in that even five years ago, there was nothing of comparable hour-long quality on TV in reruns. There were no reruns of CSI, House, The Shield, West Wing, Homicide, LOST, 24 — none of that. If you wanted an hourlong show on a cable channel, it was going to be the Dukes of Hazzard or Murder She Wrote or The Pretender. Usually either ancient shows or shows made for ancient people. So given that, I watched a lot of Law & Order reruns over again. I'm not alone. There are others. Many of whom are far worse.
I'd wager that I probably saw the first eight seasons of the original show at least three times each, and the first three seasons of SVU — before it got ridiculous — roughly the same number of times. (In my defense, I was probably sitting at the computer and making fun of people while they were on, so it's not like I was just sitting and absorbing these things over and over.) All of which logically puts me at somewhere around 12+ hours of continuous doink-doinks in my lifetime. Imagine being strapped down and forced to listen to it continuously. I have every confidence that they did this to someone at Guantanamo.
Basically, I wish I had never thought of this, because now I feel like an ass. On the other hand, I have never watched animes. So I come out a winner.