Could ultrasound be causing some people to suffer? PlayFull TranscriptDownload Ultrasound is any noise with a pitch higher than 20 kiloHertz - that's 20,000 waves per second. These sounds are beyond the normal hearing range of humans, but despite being silent, exposure to it has been linked to symptoms such as nausea, headaches and fatigue in a small percentage of people. And now a review published this week is calling for measures to limit people's exposure to the sounds.