This is accomplished through hardware so that the microphone becomes physically disabled from the rest of the MacBook hardware every time the lid is closed, preventing any software from engaging the microphone when the user shuts the MacBook. Apple points out that the camera is not disconnected in hardware, because its field of view is already completely obstructed when the MacBook lid is closed.
All Mac portables with the Apple T2 Security Chip feature a hardware disconnect that ensures that the microphone is disabled whenever the lid is closed. This disconnect is implemented in hardware alone, and therefore prevents any software, even with root or kernel privileges in macOS, and even the software on the T2 chip, from engaging the microphone when the lid is closed. (The camera is not disconnected in hardware because its field of view is completely obstructed with the lid closed.)Apple says that the T2 chip gives Macs a solid foundation for encrypted storage, secure boot, and Touch ID, all based on dedicated security hardware and the Secure Enclave coprocessor included on the T2 chip. Combined with the security and convenience of Touch ID, Macs with the T2 chip provide "a level of privacy and security protections never before seen on Mac," according to Apple.
Besides its security features, the new 13-inch MacBook Air includes a Retina Display, two Thunderbolt 3 ports, a headphone jack, 50 percent smaller display bezels, a reduced footprint, and more. Pre-orders for the device are live today, starting at $1,199.00, and the MacBook Air will officially launch on November 7.