The iPhone 4 has fantastic noise cancellation. But how it pulled that off had been a mystery, as teardowns couldn't find an audio processor. Turns out, it's a familiar piece of hardware we've seen before.
The sleuths at iFixit found that a mystery part labelled 10C0 01S8 0077 that matched nothing in their database is in fact an Audience low power audio signal processor, the same chip found in the Nexus One. Mystery solved! [iFixit]