Nexus One's high call quality depends on this one chip2
Those who have had the pleasure of using the Nexus One know that the voice quality on the handset is outstanding, Even loud background voices and noises will not prevent both sides from hearing each other clearly. For this, Nexus One users have the Audience A1026 voice processor to thank. Even though Google mentioned that the phone would contain the chip on launch day, the news was overshadowed by the distribution process of the phone and some of its other qualities. If you don't have the N-One to play around with, you can go to the Audience demo site at the source link, and play the A/B clips of calls that show the difference in voice quality between a phone using the Audience A1026 and one that doesn't use it. In an email to MobileBeat, Audience says that the chip is based on the intelligence of the human hearing system and uses two microphones on a single chip to determine the primary voice in a conversation and eliminate all of the other background noises. Volume and equalization are adjusted during a call in order to make the conversation clear. Audeince is based in Mountain View, the same location where Google resides.
source: Audience via MobileBeat