Device and method to determine a swim metric

A device for determining a swim metric, the device comprising:

• a three-axis accelerometer configured to measure three-axis inputs signals;
• and
• a controller that receives the three-axis input signals from the three-axis accelerometer, the controller being configured to:
• generate filtered input signals by filtering a first axis of the three-axis input signals to remove stroke characteristics from the three-axis input signals,
• generate a first output signal that is agnostic to a type of swim stroke employed by a swimmer by applying a first statistical module to the filtered first axis of the three-axis input signals;
• generate a second output signal by applying a second statistical module to the first output signal;
• calculate an adaptive threshold value as a multiple of the second output signal;
• determine the swim metric by (i) comparing the first output signal with the adaptive threshold value, (ii) determining turn characteristics based on values of the first output signal that exceed the adaptive threshold value, and (iii) determining the swim metric based on the turn characteristics;
• validate the swim metric by processing a second axis and a third axis of the three-axis input signals;
• and
• operate a display device or sound device to output depending on the swim metric.