Every wand I've ever used has a volume control and an LED. You can adjust the volume control so that the loudest signal turns on the LED, and you can do this during test so the LED shows which is strongest when it's hard to tell by ear, for instance if it's noisy in the test environment.

(The first wand I ever saw was on the ground near a telephone pole, with no phone man in sight. I was about twelve when I found it. It used tiny vacuum tubes and had a tiny 90 volt battery for plate voltage and another battery for filament voltage. And it was about the same size and shape as today's wands!)