Bats and dogs can hear sounds well beyond what humans can. Police use a special whistle that dogs respond to but is silent to humans. Which property of sound is at work?
AThe whistle is too loud for humans (decibels)
BThe whistle vibrates without a medium
CThe whistle has a frequency above 20,000 Hz — ultrasonic for humans, audible to dogs
DThe whistle is too small for humans to hear
Answer & Solution
Correct answer: C. The whistle has a frequency above 20,000 Hz — ultrasonic for humans, audible to dogs
The dog whistle produces sound of frequency in the ultrasonic range (above ~20 kHz). Dogs can detect this; humans cannot. Loudness is irrelevant — even a loud ultrasound sounds silent to us.
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