Ear potential that is transmitted along the spiral ganglion, which sends information through the auditory portion of the vestibulocochlear nerve to the temporal lobe of the brain. The human ear can generally hear sounds with frequencies between 20 Hz and 20 kHz (the audio range). Sounds outside this range are considered infrasound (below 20 Hz) or ultrasound (above 20 kHz) Although hearing requires an intact and functioning auditory portion of the central nervous system as well as a working ear, human deafness (extreme insensitivity to sound) most commonly occurs because of abnormalities of the inner ear, rather than in the nerves
500 kHz for the use of 500 kHz first appeared in the second Berlin International Radiotelegraphic Convention, which was signed November 3, 1906, and became effective July 1, 1908. The second Service Regulation affixed to this Convention designated 500 kHz as one of the standard frequencies to be employed by shore stations, specifying that "Two wave lengths, one of 300 meters [1 Mc/s] and the other of 600 meters, are authorized for general public service. Every coastal station opened to such service shall use one or the other of these two wave lengths." (These regulations also specified that ship stations normally used