| Most pneumatic isolators operate effectively above several hertz, but at their natural frequency they actually provide some amplification. |
| A gravity wave with a frequency of 1,000 hertz, for example, spans nearly 200 miles from peak to peak. |
| And he actually employed a 27 hertz frequency through the first part of the film to induce unease. |
| And the dog whistles are usually in the vicinity of about 40,000 hertz, which is, you know, out of our hearing range but well within the dog's hearing range. |
| At random times the program changed the dot's frequency up or down by up to a few tenths of a hertz. |
| The sounds and charges transmit in the low frequency range of 20 hertz, which is barely audible to the human ear. |
