The needle of the speed-indicator flicked and wagged to and fro; the cinders rattled on the roof, and a whirl of dust sucked after the whirling wheels, The crew of the combination sat on their bunks, panting in their shirt- sleeves, and Cheyne found himself among them shouting old, old stories of the railroad that every trainman knows, above the ...
One of the main drawbacks to a digital TV signal or digital cable signal, for instance, is that it is an artificial reproduction of the original data, whereas an analog signal starts out as an exact copy of the original.
An electromagnetic (EM) wave is not a sound wave. A sound wave is mechanical energy, and an electromagnetic wave is electromagnetic energy. The EM wave could be a radio or light wave, but in any case, it is composed of moving electric and magnetic fields. This electromagnetic wave can move through air or the vacuum of space, but sound (or any mechanical wave) must have a medium to travel through.