‘Member Magic Eye pictures? I ‘member. You may not realize it, but the new iPhone 7 you’re carrying has something in common with the visual phenomenon of the 1990s.

As a side note, the phone also has no headphone jack, which I find annoying. If you want to use your existing headphones, you’ve got to get an adapter with a tiny little digital-to-analog converter (DAC) on board. Otherwise you need to get new headphones with the lightning cable and a DAC installed. I’m not big on this because, for just one of many reasons, the DAC and/or an amp installed inside headphone cups will take up precious space that otherwise would be helping make bass.

Apple and equipment makers worldwide are figuring out their next steps for accessory integration. But back to the opening above, with the iPhone 7, Apple has certainly perfected one cool feature of modern life, and it does have something in common with the optical illusion images from the ’90s.

Called active noise reduction or active noise cancelling, the iPhone and other modern phones (and many nonphone products) incorporate a trick on the human brain that is benign and effective. Whereas the Magic Eye images mostly contained 3-D renderings of a boat (it’s a schooner!) or a four-leaf clover, the audio brain trick featured in the iPhone soothes your soul.

Ever been in a loud environment and tried to focus on a person you’re talking to? If the background noise is too loud or you’re too far away from your friend, the brain really gets taxed trying to sort out the parts to focus on versus the noise.

Sound is simple: It’s just vibrations in the air, which move a bit like waves in a pool after a rock is thrown. The waves that are taller sound louder, and the waves that are longer sound lower in pitch. We can hear air vibrations when their speed is between 20 per second and 20,000 per second — the audible range humans.

The waves are also like water waves as there is a crest and a trough to each one. Long ago, scientists discovered that if you take two versions of the same sound and delay one ever so slightly — you align it so the trough of one matches the crest of the other — the resulting effect to our ears is complete silence.

This can be done in the analog or the digital domain, and these days, active noise cancellation is used in all kinds of things, from mufflers to airplane cabins to cars. But Apple has really taken charge of the technology for phones, and the iPhone 7 offers the best application of this technique for phones yet.

In case you didn’t notice it, there is now a second microphone on the back of the iPhone 7 that listens for ambient noise and sends that to the processor. What you end up experiencing, even in the midst of a terrible din, is the soft, familiar voice clear as a bell on the other end of the line.

Ahhhh. We’ll dive a little deeper into digital signal processing (DSP) next week.

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