Soon silence will have passed into legend. Man has turned his back on silence. Day after day he invents machines and devices that increase noise and distract humanity from the essence of life, contemplation, meditation.

This quote is saying that people are becoming so used to having noise around them, that silence–which can be calming and helpful to concentrate and reflect–is becoming forgotten. Machines, devices, and other forms of technology increase noise and cause distraction, so people are less likely to slow down and spend time in silence.