Amazing - Modem Sound Slowed Down 700%

[∞♥ 17]

I always liked the way the modem sounded when it connected...now I know why.

[IR5FORMUMSIE 850]

I always liked the way the modem sounded when it connected...now I know why.

I'll stick to my theremin, thank you very much.

[JimVaPhuong 4,863]

Definitely eerie sounding, but it's not a modem "slowed down 700%". Hang on while I dig out my audio engineering and computer scientist hats...

It's not possible to slow something down 700%. It's not possible to slow something down more than 100%. If you slow something down 100% then you've stopped it completely. Therefore, it's impossible to tell for certain what rate this was originally recorded at, and what rate it was played back at in order to get this sound. However, just so that doesn't stop us from going any further, let's presume it was played back at 1/7th of it's recorded rate. That should mean we can increase the rate 7X (700%) and it should sound like a modem again, right.

Wrong.

I tried doing exactly that. I recorded the sound from the video using Sound Forge and then changed the playback rate to be 7X the recorded sample rate. I then ran a frequency analysis on the sound and found significant audio content all the way up to 24kHz. What difference does this make? Well, the bandwidth of a telephone line is 3kHz. While the signal you send down a telephone line can consist of multiple frequencies (which is exactly how a 56K modem works), it can't contain any single frequency above 3kHz. Frequencies above that won't pass through the amplifiers in the telephone company's switching station.

A biased observation - the sound at 7X playback rate doesn't sound anything like a 56K modem. It has piercing high frequency squeals and whining, and it's not at all rhythmic like the sound of a modem. The person who created this sound may have started with the sound of a 56K modem, but he/she did an awful lot of processing to it before they got the sound you hear on that video. It contains high frequency sounds and reverb which would not be present in a recording of a 56K modem.

Anyway, this video has been making the rounds since it was original posted in February, and I'm not the first one to have looked into it. It's definitely an interesting sound. It's just not what you think it is.

[∞♥ 17]

I'll stick to my theremin, thank you very much.

Gotta love the theremin

[∞♥ 17]

Definitely eerie sounding, but it's not a modem "slowed down 700%". Hang on while I dig out my audio engineering and computer scientist hats...

It's not possible to slow something down 700%. It's not possible to slow something down more than 100%. If you slow something down 100% then you've stopped it completely. Therefore, it's impossible to tell for certain what rate this was originally recorded at, and what rate it was played back at in order to get this sound. However, just so that doesn't stop us from going any further, let's presume it was played back at 1/7th of it's recorded rate. That should mean we can increase the rate 7X (700%) and it should sound like a modem again, right.

Wrong.

I tried doing exactly that. I recorded the sound from the video using Sound Forge and then changed the playback rate to be 7X the recorded sample rate. I then ran a frequency analysis on the sound and found significant audio content all the way up to 24kHz. What difference does this make? Well, the bandwidth of a telephone line is 3kHz. While the signal you send down a telephone line can consist of multiple frequencies (which is exactly how a 56K modem works), it can't contain any single frequency above 3kHz. Frequencies above that won't pass through the amplifiers in the telephone company's switching station.

A biased observation - the sound at 7X playback rate doesn't sound anything like a 56K modem. It has piercing high frequency squeals and whining, and it's not at all rhythmic like the sound of a modem. The person who created this sound may have started with the sound of a 56K modem, but he/she did an awful lot of processing to it before they got the sound you hear on that video. It contains high frequency sounds and reverb which would not be present in a recording of a 56K modem.

Anyway, this video has been making the rounds since it was original posted in February, and I'm not the first one to have looked into it. It's definitely an interesting sound. It's just not what you think it is.

Jim,

I had wondered about this...I just heard this last week and haven't had a chance to install sound forge on my new machine. I was going to record a modem and see what happened when I ran it through sf. Just never got around to it. They would have probably used the pitch shift effect...and probably added some reverb...just my guess.

I just added the title from the vid that's making the rounds. I'll install sf and see if I can reproduce it.

Thanks for the info!