This vibrates the cone which creates the sound waves. Sound waves can reflect off surfaces. We hear reflected sound as an echo. Hard, smooth surfaces are particularly good at reflecting sound.

Because these time reflections require a uniform variation across an entire electromagnetic field, scientists assumed it ...

Ethereal sounds echo from 17 sound installations hidden amongst the ... Climb inside an oversized metal cylinder, where you can feel the sonar waves pulse through the enclosed air.

And the results are over 95% accurate." An echo test involves ultrasound-- high-frequency sound waves -- to evaluate the function of heart muscle and valves, the same technology used to ensure a ...