You hear it every time you get a text message or alert. It's arguably the most iconic noise associated with the iPhone: The default "Boo-Dah-Ling" that plays when you get a text message or alert. But who designed it? A fascinating post from the audio designer behind the legendary tone explains all.

According to Kelly Jacklin, the founder of audio-visual software studio Jacklin Studios, he designed the "tri-tone" noise in 1999. It all began when a friend, who was developing a music app called SoundJam MP, asked him to create a noise that would play when a disc was finished burning. His whole technical explanation is fascinating, but here's the gist for the non-audio engineers among us:

I was looking for something "simple" that would grab the user's attention. I thought a simple sequence of notes, played with a clean-sounding instrument, would cut through the clutter of noise in a home or office... I was really into the sound of marimbas and kalimbas at the time, so I thought I'd try both of those... For the notes, I wanted a 3-note sequence, or perhaps 4 notes. I was going for simple, and didn't have much time to devote to being creative, so no fancy timing here, just sequenced notes. I wanted a happy feel, so notes from the major scale, focussing on I, III, IV, V, and VIII (the octave).

Jacklin's creation was shipped as a burn-disc noise on SoundJam, but that was only the beginning of its life. Soon after its release, Apple bought the app and hired some of its creators, and when iTunes was released, Jacklin was surprised to find that his noise was still being used for burning discs. Then, Apple added the noise to indicate the installation of new software in OS. Finally, in 2007, Jacklin was amazed to discover his audio design—renamed "Tri Tone"—being used as a default text message alert the first generation of iPhone.

"Wow!," he writes. "Who'd have thought?" Read Jacklin's full post here, and check out the bonus at the end—he's uploaded some of the sounds she considered using instead. We could've ended up with a very different noise! More on Apple sound design is here and here. [Twitter]