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 contacts were to be initiated on this frequency, although once established the participating stations could shift to another frequency to avoid the congestion on 500 kHz. To facilitate communication between operators speaking different languages, standardized abbreviations were used including a set of "Q codes" specified by the 1912 Service Regulations. Article XXI of the Service Regulations required that whenever an SOS distress call was heard, all transmissions unrelated to the emergency had to immediately cease until the emergency was declared over. There was a potential problem if a ship transmitted a distress call: The use of 500 kHz as a