US Patent 9361885 Methods and apparatus for detecting a voice command

Some aspects include a method of monitoring an acoustic environment of a mobile device operating in a low power mode, the mobile device having a first and second processor, the method comprises receiving acoustic input while the mobile device is operating in the low power mode, performing at least one first processing stage on the acoustic input using the first processor, prior to engaging the second processor, to evaluate whether the acoustic input includes a voice command, performing at least one second processing stage on the acoustic input using the second processor to evaluate whether the acoustic input includes a voice command if further processing is needed to determine whether the acoustic input includes a voice command, and initiating responding to the voice command when either the at least one first processing stage or the at least one second processing stage determines that the acoustic input includes a voice command.