Previously, Google had revealed the existence of the microphone in any of its product descriptions, but had stated that it was not a "secret".
"The built-in microphone in the device was never intended to be a secret and should have been included in the technical specifications – it's an error on our part," CNN Business said on Wednesday. Google spokesperson.
The microphone is not enabled by default and can only be enabled when users enable the option. A Google spokesman said the microphone was built into the device, providing users with additional features, such as the ability to detect broken glass during a break-in.
"Security systems often include microphones to provide features that rely on sound detection," the spokesman said.