On the CDC 3800, the top three bits of the accumulator were scaled and summed by a set of three resistors, then fed into the console speaker.  Generally, this produced noise of very little interest (except to indicate that the machine was running).

However, when I ran my Shellsort (https://en.wikipedia.org/wiki/Shellsort <https://en.wikipedia.org/wiki/Shellsort>), the speaker made a very distinctive sound.  It was a series of rising tones whose durations got shorter and shorter.   Something like Vwooooooooooop, Vwooooooop, Vwooooop, Vroop, ...

-r