While really white bright will jam your eyes too, an ultrasound will not jam your ear, hence this is actually easier to overcome. Just use dumb microphone, that

While really white bright will jam your eyes too, an ultrasound will not jam your ear, hence this is actually easier to overcome. Just use dumb microphone, that will cut frequencies over 10Kz and have the unintended secondary effect that Alexa will be even cheaper.