So what exactly causes that noise when your connecting?

They’re pretty oboxious on dialup modems anyway. Roars and screeches greet me when I connect. I notice it’s the same on many other computers.

So anyone know exactly what causes those noises?

That is known as a handshake – the two modem are “talking” to each other to decide on what protocols will be used, how fast they will be trading data. There is an option to turn the speaker off if you don’t want to hear this noise

cable modems=you are always connected:D
and kin is right, you can use the noises to identify what is wrong when you try to connect.

Would that I could turn my curiosity off as easily. :slight_smile:

The devil you say!

Really? Like, you can identify the problem (“Hear that rising tone at the end? Your four-axis minervinator is loose.”), or that the computer can?

What the funk is a minervinator?

If you’re familiar with the sounds, you can find problems this way. Not problems of loose wires, or broken hardware, but wrong baud rates, wrong negotiation, etc. You can sometimes tell what baud rate the connection is, too.

Another fun thing is to set the modem to leave the noise on ALL the time, not just the beginning. Then you can hear the data going by :slight_smile:


It depends on what noises. Usually one can use the noises to determine if the two modems are having trouble handshaking (incompatible protocols, for instance), if the connection problem is with the authentication (username/password) process, and the like. If a VERY unusual noise pops up, it may be an indication of a bad modem as well. However, a tech isn’t going to listen to the noises and then respond with “Oh, you have a broken oscillator on your modem board.”; the noises can’t tell you something like that.

I’ve never been able to get anything meaningful out of modern modem noises, but I remember back when I did the BBS thing with a 2400 baud modem I could, for example, recognize by sound when the other modem was trying to connect at 300 or 1200 baud. It’s not like you can hear the bits going by or anything…

And those noises don’t just take place while you’re connecting either. They continue for the entire time you are connected, but you generally don’t hear it through the computer except for the first few moments. Some programs have options to let you hear the modem noise all the time, if you happen to like it. The noise itself is data encoded in audio form. The simplest kind of encoding is using two different types of tones, one for a 0 and one for a 1, but that isn’t used anymore because it’s slower than shit.

In somewhat the same vein, when I was a kid we used to get wrong-number fax calls not infrequently. With some practice, I was able to whistle my way through most of the handshaking process. I can’t do it with newer fax machines or modems, though. They’re probably more strict in what they’ll accept.

I’ve wondered the same thing about the sound you hear, but what I want to know is, exactly what is the mechanism for creating the sound- it has to come from somewhere.


For most PC modems there’s a speaker on the modem card. Some modem cards (and most laptop modems) pass the sound through the PC sound card, to avoid the expense of a speaker. Then, your PC speakers are playing it.

If you meant what is generating the tones themselves, not what’t playing them-- the modem itself contains a DSP (digital signal processor) which is basically a small computer on a chip, dedicated to making the modem work. This chip is running modem software stored on the modem, which is programmed to produce certain tones and patterns for certain conditions, and to encode data.


The long answer:

The telephone system is built to carry sound. When you need to send computer data by telephone, you have to turn the data stream into sound, then let the phone system carry it to the other computer, which turns it back to data. The data->sound converter is called a modulator, and the sound->data converter is called a demodulator. Usually you build both functions into a single product called the modulator/demodulator, or modem for short.

So the modem is just using the phone system just as a human would - it dials a number, then sends and receives sound. Until a connection is made, all the sound sent and received by the modem is also sent to a little speaker on the modem so the user can hear what’s going on.

So what’s the use? Well, if you input a wrong number into the computer, the modem may connect to a voice phone. You would hear “Hello? Who’s this?” instead of all that screeching. Or if the phone line is down, you may instantly notice that you are not getting a dial tone. If you have trouble connecting, you can hear if the other computer is at least trying to answer, or if it’s not even picking up the phone - and if it is answering, if you are getting as far as the screeching part (handshaking) or failing at some point before that.

Just wondering - my modem speaker is set to “off” and i still get to hear the handshake…i suppose this should be a different thread, but does anyone know why “off” means “still kinda irritatingly loud”?

There are two places to change the volume of the modem - one is in your modem software, and one is in the Modems section in your Control Panel. I expect there is an equivalent in Macs.

One overrides the other, but I dunno which.

aha, when the computers connect they talk to each other & ask each other how fast they want to connect, etc. I;m pretty sure some hackers use that time to hack into the remote system by having their computer have a little chat with the other one. I forgot what its called when the modems do this.

I always heard it was the modemon making that noise. It does sound kind of satanic, doesn’t it?

this is umpteenth time we discuss this so I won’t repeat myself. It has all been explained in detail already. I even posted some links to audio files of different handshakes.