Are there sounds we can’t hear?
　 　 　
You might be surprised to learn that there are sounds that human ears can’t hear. These sounds are called ultrasonic and infrasonic sounds. These are sounds that are either too high or too low for human ears to hear. There’s a limit to how high a pitch humans can hear. We can’t hear sounds higher than that limit. But what are these sounds that we can’t hear? Infrasonic sounds are less like sounds and more like gusts or billows of air. People don’t even recognize these as sounds. Ultrasonic sounds include the sounds dolphins make to talk to each other and the sounds bats use to find food. Another example are the ultrasonic sounds boats use to find fish. Wouldn’t it be cool if we humans could listen in on dolphins’ conversations?