Because their hearing apparatus (ear) is not tuned to hear ultrasound.
Unable to hear.
Bats. They are blind and use echolocation to navigate when they are flying. They emit high pitched sounds humans ears are unable to hear. The sound frequency in a human voice is too low pitched for them to hear.
Unable to hear.
humans are unable to see things that are too small, walk long distance and hear somethin too soft or too far away.
Deafness is when somone is unable to hear anything.
Yes, they can. They have the ability to hear the heartbeat of a mouse, so a human heart wouldn't be a problem for them to hear.
The highest pitch that a human can hear is around 20,000 hertz.
bat
A human can typically hear a range of about 10 octaves in total.
In a vacum. in a vacum.
Able means "can do". Unable means "cannot do". This could refer to an action, behavior, speech, etc. Examples: I'm unable to say why the experiment failed. I'm unable to walk. I'm unable to hear. I'm unable to move. I'm unable to feel.
The highest frequency that a human can hear is typically around 20,000 hertz (Hz).