Sculk Sensor with malfunction

Sensors have a range of 8 blocks

although the post did say Radius, this appears to be 8 in diameter

I know that. However, the Sculk Sensor does not always detect sound, that is the question. Just look at the screenshots

The Sculk Sensor isn't supposed to detect sound, it is supposed to detect vibrations

Vibrations in this case mean significant physical motion or activity. A Sculk Sensor, therefore, wouldn't detect the moo of a cow.