There has been some misleading information about how far ultrasonic sounds can be heard, so I googled "How far can a canine hear a silent dog whistle?" This is what I found. I wonder just how far the ultrasounds of the FREQ can be heard since they are amplified?

https://www.lsu.edu/deafness/HearingRange.html

https://physics.stackexchange.com/questions/52195/ultrasonic-wave-through-air

So dogs hears 50khz about 250 yds with 194 Db undistorted sound. Varies some by breed.
Have take into account the directivity of sound, lower is less directive. 194Db low freq is spread around 270 deg but ultrasonic is usually a much narrower beam.