Always-on detection systems

A system for providing an acknowledgement output at a haptic output transducer of a device in response to detection of a trigger signal, the system comprising:

• an input transducer;
• a signal processor coupled to the input transducer;
• a main processor separate from the signal processor;
• an output driver;
• and
• a memory, wherein the memory is configured to store one or more acknowledgement signals corresponding to the acknowledgement output, wherein the signal processor is configured to:
• monitor an input signal received at the signal processor from the input transducer;
• and
• if the received input signal corresponds to the trigger signal:
• retrieve, from the memory, an acknowledgement signal comprising a haptic waveform corresponding to an acknowledge effect to be output by the haptic output transducer;
• output the acknowledgement signal to the output driver to cause the output driver to drive the haptic output transducer to output the acknowledgement output;
• and
• output an interrupt signal to the main processor to cause the main processor to enter an active state, wherein the main processor is configured to transmit the received input signal to a server for verification that the received input signal is a valid audio trigger.