high frequency sound on a tv advert

A dog food company has launched the first TV advert aimed directly at dogs themselves.  The advert’s soundtrack includes sounds with frequencies in the range 18 000 to 20 000 Hz (18-20 kHz).  Dogs can hear sound with frequencies greater than 20 kHz, we call this ultrasound.

I found a copy of the advert on Youtube.  The upper limit of human hearing is 20 kHz, so some young people should be able to hear the sounds for themselves even though adults can’t.  Can you?

Now let’s see what happened when the BBC Newsround team filmed some dogs while the advert played in the same room.

You might have used a signal generator in class to discover your personal upper frequency limit.  The video below has a soundtrack that starts at 1 Hz and sweeps up to 20 000 Hz, before sweeping back down to 1 Hz again.  For how long can you hear the sounds?