Modem dialup sound slowed down 9000%

If you ever connected a computer to the Internet before everything was online all the time (pre-2000), you probably remember that you connected the computer to a phone line via a modem. This modem made an odd sound when connecting, that sounded like this:

I’m not going into the details about what happens in that 20 second audio. That is something you can learn all about here. That site even made a nice poster for it too:

What I wanted to do with the audio, was to slow it down a few times. How would I do that, and how would that then sound? I’ve heard other audio slowed down, like the Windows 95 start up sound, slowed down 4000% for example:

I tried with a few different stretches, from 20 seconds to 30 minutes at most (9000% increase). Safe to say the new versions are pretty spooky-sounding.

10 times longer or 3 minutes long

30 times longer or 9 minutes long

100 times longer or 30 minutes long

So, how did I do it?

You might ask how do you do such a enormous stretch to a song or audio file. There is the Sox audio software on Linux, but this were not quite up for the job. Then I came across a Python script that utilizes the scientific libraries SciPy and NumPy to create (read mathemagical) a new waveform from the initial one. This was pretty impressive and quick too.

By hoyd

Communication adviser at Andøya Space.