1. explanations and experiment

6. Medical sonography ( ultrasonography ) is an ultrasound-based diagnostic medical imaging technique used to visualize muscles, tendons, and many internal organs, to capture their size, structure and any pathological lesions. Ultrasound has been used by radiologists and sonographers to image the human body for at least 50 years and has become one of the most widely used diagnostic tools in modern medicine. The technology is relatively inexpensive and portable. The creation of an image from sound is done in three steps - producing a sound wave, receiving echoes, and interpreting those echoes.

7. An inventor from Peterborough created a clever device to keep people safe from dog attacks. Richard Wylie (64) hopes the electronic ‘Dazer’ device will be used to safeguard people from dangerous animal attacks. The device emits an ultrasonic blast that is inaudible to humans but makes animals very uncomfortable– acting as a perfect defence if they become aggressive. “ The device helped to save my wife and son Dax from getting attacked by monkeys. “ We were up on the rock of Gibraltar and my wife was holding a banana. The monkeys crowded around them and were going wild. Luckily I had the Dazer and that sent them away.” f(dazer)=23,5 kHz,