[Editor's Note: Once again, we've invited Danger, Inc., sound designer Peter Drescher to predict the future of mobile audio. We think you'll agree that his latest prophecies are both tantalizing and frighteningly plausible. This essay is based on his October 2007 Audio Engineering Society presentation "Game Audio for Broadband Phones."]

I recently got an iPhone, in part because it reminds me so much of the Star Trek data PADD, a fictional technology consisting of a thin slab of glass and plastic, which is held in one hand and tapped on with the other (see Figure 1).

Fig. 1: Pod vs. PADD

Fig. 1: The iPhone is practically a prototype of the Star Trek PADD.

The PADD (Personal Access Display Device) rendered any kind of information, in a variety of formats, via a subspace connection to the central computer. The interface was gestural, multi-touch, and self-configuring. Of course, there was no keyboard and, in fact, no typing was ever required. It's irrelevant to enter text by hand when there's perfectly accurate voice recognition and transcription services built in to the device.

While the iPhone may not be up to 24th-century standards, the technology is obviously heading in that direction, and I love it when science fiction invents reality. However, the laws of physics currently prevent even the most futuristic phones from generating loud, high-fidelity audio. Despite sophisticated techniques and materials, no cell phone speakers will ever be good enough for anything except producing annoying ringtones.

This is because sound production is all about pushing air, and the tiny bits of vibrating metal and plastic that pass for loudspeakers in mobile devices are incapable of pushing very much of it. Nor can they produce frequencies below about 200Hz, meaning no bass or kick drum in your music mix, nor engine rumble or explosive thud in your game soundtrack. Think of it this way: a speaker the size of a dime simply cannot produce a six-foot long wave.

Headphones vs. Speakers

Unless, of course, you stick it right in your ear! Then the amount of air-pushing needed decreases dramatically. Suddenly, you can fit an entire symphony orchestra in your head, with a flat response, full frequency range, and volume AS LOUD AS YOU FREAKIN' WANT IT! Music playback on cell phone earbuds is already about as good as it gets, because streaming full-resolution audio out of flash memory doesn't take much power or CPU.

Headphones are great when you want to block out the world and listen to music. But the problem with headphones is that they are exclusive, insulating, and antisocial. That's fine for many situations, but people also like to share their music with their friends. Sure, you can send them a link or put the tune on your MySpace page, but it's much more fun to play it for them in person and see their reaction. One of the reasons portable multimedia devices are so popular is because they provide a neat solution to a social problem that everybody has, namely: "how do I show off how cool I am?"

To paraphrase H.L. Mencken, nobody ever went broke overestimating the vanity of the American public, and broadband phones are the perfect attention-getters. Here, look at pictures of my dog, isn't he cute? Hey, listen to these grooves I downloaded from iTunes! C'mere, check out this Weird Al Yankovic video on YouTube! [Note the O’Reilly shoutout at 1:12. —Ed.]

But there is an obvious problem with sharing media like this, which is: You Can't Hear for Squat on cell phone speakers. To really grab your attention, the audio has to be loud enough to annoy the living crap out of the guy sitting next to you. Lucky for him, trying to produce really annoying volume levels using tiny speakers is usually an exercise in futility. Some might consider this a good thing for polite society, yet the desire to share our noise remains.

Sharing Earbuds

Have you seen advertisements featuring happy couples like the one in Figure 2, sharing earbuds?
Fig. 2: Headphone sharing

Fig. 2: Back to mono(nucleosis).

That's lovely and romantic if you want to get your head next to some hot girl, but it's not something you want to do with everyone. There's a television commercial featuring a big sweaty meathead jock, at the gym, pumping iron, endorphin grin on his face, a wild look in his eye, yelling at the camera, "Hey dude! Check out this groove I just downloaded, it totally rawks!" Then he pulls the sweaty earbuds out of his head and moves to stick them into yours — and I'm thinking, "Dude, I use my ears for a living. Get those disgusting things away from me!"

Sharing earbuds does not solve the problem of how to make a cell phone act more like a boombox. Some manufacturers try to make the phones louder by increasing the speaker size. Others install two speakers for stereo playback, though given the palm-width speaker separation, you don't get true stereo, you just get double loud. Some models apply "3D" audio processing to provide a (slightly) increased sense of presence and space.

But it's all ultimately pointless, because if you really want to listen to your music, movies, or game soundtracks, you're gonna have to use...

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