The patent describes the sensors as having accelerometers which can detect vibration in the skull of the wearer while a conversation occurs. Upon detection, it will then identify speech and will distinguish it from other ambient noises, classifying such as non-vocal.
Apple will also incorporate the use of multiple microphones for enhanced voice detection on either side of the earbud. There's even an option to add embedded mics throughout the earbud cable in order to create a sort of beamforming mic array. This type of feature is categorized under a professional mic setup which is an essential tool for capturing and isolating high quality audio.
The accelerometer can be tuned to sample vibrations that are in low frequency which shall indicate voiced and unvoiced signals of speech. Once the output signals are measured, the accelerometer can effectively create a voice activity detector (VAD) that is accelerometer-based. Through this, it can start discerning whether the sound is a voiced speech as indicated by ambient vibrations. This means that the system will have the ability to choose which one to exclude and which one to pass on to a caller on the other line when a conversation is taking place.
An array of microphone is then used to track acoustic signals for the wearer's voice. A single earbud can be equipped with both front and rear-facing microphones. It can also have optional embodiments such as several sets of mics that are sprawled along the device cable. When used simultaneously, they can create a beam forming array.
To alleviate the errors in voice pickup, the technology uses the system of comparing and contrasting between the microphone output signals and the accelerometer. This means that the final VAD output becomes an "and" function of the VAD systems. A threshold analysis is then applied to the power signals which then become a speech-to-noise power signal. The latter can then be placed in a noise suppression module. In order to get an accurate ambient noise assessment, a spectral mixer is utilized to come up with a final output signal. This is done by removing the respective noise power signals that come from both the accelerometer power signals and the microphone.
Apple also added that there are several other types of headphones which can be compatible with the new technology. These would include the closed headphones which are similar to those that are made by Beats and the single earbuds such as the Motorola Hint.
It's not yet clear whether Apple will make headsets with the bone conduction technology a reality. So far, the company had already included the noise cancellation feature in its devices which can be seen in its lineup of MacBook and iPhone products.
