Three Beeps = Cell Phone Dial Tone

By Peter Drescher
May 15, 2012 | Comments: 1

"Cell Phone Dial Tone" is an oxymoron, like "jumbo shrimp". Dial tones are analog, cell phones are digital. A dial tone signals an open connection to a landline telephone network. A cell phone sends packets of voice data back and forth via wireless network. The technologies don't intersect ...

Except in the movies.

I like to watch the "user experience" behavior of people using cell phones in movies, while listening to the accompanying sound design. Since these are fictional characters and devices, they work in a way that best serves the narrative. But they also provide useful examples of how we expect cell phones to function in the real world.

For example, there's a scene in Bulworth (1998), where Warren Beatty is talking to Halle Berry on a cell phone. He flips it closed in the middle of a sentence. Cut to: Halle's reaction in the limo -- she pulls the phone from her ear and stares at it with an astonished expression of "Oh no you didn't!!" while the soundtrack plays => a landline dial tone. Of course, no cell phone has ever worked that way, but the scene demanded she be dramatically notified she's been dismissed.

On a landline, if you hear a steady tone of two sine waves (350 and 440 Hz) during a conversation, you instantly know your call has been rudely interrupted. In contrast, when a call was dropped by a cell phone circa 1998, usually the damn thing wouldn't make any sound at all. Modern devices are more sophisticated, and so, on the iPhone, when a call is dropped, you get three beeps.

Beep Beep Beep

I can't take credit for this, because I didn't quite get it right. When designing the dropped call sound for the T-Mobile Sidekick a decade ago, I had it take the form of "tone + 3 beeps at contrasting interval", so that sonic distinction could be made between the states "call ended" (you hung up), and "call dropped" (you got hung up on). Looking back, that was way too much information, and when the iPhone released with "3 beeps = call dropped.", I immediately recognized it as the better solution.

I call the sound a "cell phone dial tone" because, during conversation, three beeps serves the same notification function as the landline tone ... and prompts the same reaction ("What the!?" [redial]).

There's another good reason the sound exists: feedback. On a cell phone, because the speaker and the mic are so close to each other, the phone application manages volume levels to prevent echoes. Basically, it turns the speaker off when the mic is recording above a certain level, preventing audio feedback.

This, in effect, creates a simplex line, a "one way at a time" connection, like a walkie talkie. I can't hear you when I'm talking, and you can't interrupt me if I don't stop. Since the speaker in your ear is always silent when your mouth is open, the only way you'll ever know that the incoming audio stream stopped while you were talking, is if you hear the three beeps.

Vox me!

It turns out that simplex connections are a excellent way to communicate using digital devices, as evidenced by the dramatic increase in downloads of Voxer. A number of my former Danger colleagues are working on this truly great app, which turns your iPhone or Android into a walkie-talkie, by recording samples of your voice, and delivering them live via cloud network. It's like texting with voice, so it doesn't use your minutes, and it's fun, particularly in group chat party line mode. And it's become an insanely popular social media app, requiring massive server farms and a gajillion bytes per second bandwidth to work.

Of course, what interests me the most is what it sounds like. In a recent version upgrade, an excellent new Audio UI was introduced. When you start recording, you get "two beeps". When you stop, you get "one beep". And when a new chat comes in, you get "three beeps".

Direct, simple, telegraphs the required information with military precision, I like it! I can't take credit for it either (despite providing some source material), but I highly approve. It works great, the sound is recognizable, it's even contextually reminiscient of an earlier incarnation of a similar technology (note: for the record, no Nextel property was used in the making of this chirp. In fact, it came from a Korg Kaossilator I picked up at Project BBQ courtesy of our friends at DTS).

The First 3 Beeps

The thing I like best about the three beep chat alert: it follows my "cell phone dial tone" paradigm perfectly. When you start a conversation on a landline, the first thing you hear is a dial tone. In fact, if you pick up the receiver and don't hear that tone, you start banging on the phone.

The landline dial tone says "your phone is now connected to the telephone network", but cell phones don't work that way. Modern devices are always connected to the network, as long as they've got signal and power. Data transfers back and forth all the time, even when you're not talking on the phone.

That's why the dial tone you hear at the beginning of a landline call would make no sense in a wireless world. Imagine if you pulled up the 12-key pad on your iPhone, and it played a steady tone until you touched the first number. You'd think it was broken ... and you'd be right.

But what about the cell phone dial tone? Voxer uses three beeps to indicate "chat channel open" when someone voxes you. It's the sound you hear before you start talking, when the call is initiated.

Dial Tone vs Ringtone

SO if you hear three beeps while you're talking, it means you're talking to yourself. But if you hear three beeps when you're not talking, it means somebody is talking to you. This makes for a nice symmetry, and reflects the two times you hear the dial tone on a landline: when you start a call, and when the call is interrupted.

Some may say I'm over analyzing this, and that the Voxer three-beeps is just another message notification, like you get from tweets or texts ... and they might be right. But the thing about a vox is that it's from a person speaking in real time. It's more like a phone conversation than a message exchange (although Voxer works both ways; that's why it's cool).

Using a cell phone dial tone for the vox ringtone is therefore a brilliant example of form following function in a remarkably cohesive manner.

The Original Three Beeps

Finally, I like the "three beeps = cell phone dial tone" idea because it reminds me of sounds made by the very first (fictional) cell phones. When you flipped open a communicator on Star Trek, it made a distinctive bleep to indicate "channel open", and it beedeebeeped again when someone contacted you. Subspace connections are rarely dropped, but whenever something did go wrong with the comm, the "connection rudely terminated" sound always took the form of (you guessed it) three beeps.

This is why I say, "Everything I know about Audio UI, I learned from Star Trek". Personally, I love it when science fiction invents reality, and it's sweet to hear the original user interface sounds reflected in modern devices ...

   - pdx

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1 Comment

As a fellow engineer I enjoyed your posting a lot, especially when you make fun of the Halle Berry incident (who cares when its Halle!!)

Anyway, I know you don't answer questions posted here willy nilly but from one ex Telecom, now RF and CM engineer what would the meaning of four beeps on a Virgin landline calling a Voda Mbile Mobile (I live in the UK).

Would love to hear back and keep up the articles!


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