Hearing range 60 decibels, the hearing range for the Senegal bushbaby is 92 Hz–65 kHz, and 67 Hz–58 kHz for the ring-tailed lemur. Of 19 primates tested, the Japanese macaque had the widest range, 28 Hz–34.5 kHz, compared with 31 Hz–17.6 kHz for humans. Cats have excellent hearing and can detect an extremely broad range of frequencies. They can hear higher-pitched sounds than humans or most dogs, detecting frequencies from 55 Hz up to 79 kHz. Cats do not use this ability to hear ultrasound for communication but it is probably important in hunting, since many species of rodents make ultrasonic calls.
500 kHz to exchange messages once contact was established. 425, 454, 468, 480, and 512 kHz were used by ships while the coast stations had their own individual working frequencies. Twice each hour, all stations operating on 500 kHz were required to maintain a strictly enforced three-minute silent period, starting at 15 and 45 minutes past the hour. As a visual memory aid, a typical clock in a ship's radio room would have the silence periods marked by shading the sectors between h+15 to h+18 and h+45 to h+48 in RED. Similar sectors between h+00 to H+03 and h+30 to h+33 are