If your matches have tested at fewer markers than you, you will want to encourage them to upgrade to see if the match holds up. You will be able to see the Most Distant Ancestor for your matches who have provided them. Look down the list to see if any look familiar.
In physics, sound is a vibration that propagates as a typically audible mechanical wave of pressure and displacement, through a medium such as air or water. In physiology and psychology, sound is the reception of such waves and their perception by the brain.
Sound is a wave that travels through a medium and carries energy from one place to another. A sound wave consists of a series of orderly oscillations of particles within the medium. These oscillations produce regions of compressions and rarefaction (high and low pressures) throughout the medium. Ultrasound is defined as a sound wave with a frequency above 20,000 cycles per second or hertz (Hz).