Up above the range of human hearing is a signal applied to the tape heads
called "bias"
so that they will work in a linear range and make the signal proportional to
what goes in the mike go on the tape..
I bet this higher than we can hear signal is perceptable to the bees and
percieved as a threat.
Most non winding watches use an oscillator and circuits to divide the
oscillations down to seconds and other fractions of time.
This amy also stimulate the bees.
Also anything shiny that moves fast is an eyeball- watchbands,crystals and
wrists.
How better to drive away an invader than to nail it in the eye?
 
Tom in CT