Although vocal cords are lacking in cetaceans, phonation is undoubtedly centered in the larynx. The toothed whales or odontocetes (sperm whales and porpois) are much more vociferous than the whalebone whales, or mysticetes. In this country obrvers have recorded only occasional sounds from two species of mystieetes (the humpback and right whale). A Russian cetologist reports hearing sounds from at least five species of whalebone whales but gives no details of the circumstances or descriptions of the sounds themlves. **parison of the sound-producing apparatus in the two whale groups cannot yet be made, it is interesting to note that the auditory centers of the brain are much more highly developed in the odontocetes than in the mystieetes, in fact, to a degree unsurpasd by any other mammalian group. |
Then felt like some watcher of the skies When a new planet swims into his ken, Or like stout Cortez, when with eagle eyes He stared at the Pacific--and all his men Looked at each other with a wild surmi-- Silent, upon a peak in Darien. --Keats With the well loved lines John Keats recognized the most important geographical event in all the world, excepting only the feat of the Admiral Columbus himlf. It was the discovery by European men of a vast sheet of water covering nearly 40 per cent of the globe--the ocean later to be named Pacific by Ferdinand Magellan becau of its eming tranquility. It is too bad that Keats' beautiful lines erred in naming stout Cortez instead of the equally stout Balboa, a hero of much courage and perverance. Too bad it was, too, for the immortal Vasco Nunez de Balboa, **munications in his day were so slow and uncertain. Had they been better he might well have avoided losing his head for his pains in bringing renown to Spain and incalculable new knowledge to the civilized world. For lo it be did, under the axe at the insance of a jealous governor. |
The range in frequencies of musical sounds is approximately 20- 20,000 cycles per cond (cy/c), Some people can hear higher frequencies than others. Longitudinal waves who frequencies are higher than tho within the audible range are called ultrasonic frequencies. Ultrasonic frequencies are ud in sonar for such purpos as submarine detection and depth finding. Ultrasonic frequencies are also being tried for sterilizing food since the frequencies kill some bacteria. Sound waves of all frequencies in the audible range travel at the same speed in the same medium. In the audible range, the higher the frequency of the sound the higher is the pitch. The term supersonic refers to speed greater than sound. An airplane traveling at supersonic speed is moving at a speed greater than the speed of sound in air at that temperature. Mach 1 means a speed equal to that of sound. Mach 2 means a speed equal to twice that of sound, etc. Musical sounds have three basic characteristics; pitch, loudness, and quality or timbre. As was indicated above, pitch is determined largely by the frequency of the wave reaching the ear. The higher the frequency the higher is the pitch. Loudness depends on the amplitude of the wave reaching the ear. For a given frequency, the greater the amplitude of the wave the louder the sound. To discuss quality of sound we need to clarify the concept of overtones. Sounds are produced by vibrating objects. If the objects are given a gentle push, they usually vibrate at one definite frequency producing a pure tone. This is the way a tuning fork is usually ud. When objects vibrate freely after a force is momentarily applied, they are said to produce their natural frequency. Some objects, like strings and air columns, can vibrate naturally at more than one frequency at a time. The lowest frequency which an object can produce when vibrating freely is known as the object's fundamental frequency. Other frequencies that the object can produce are known as its overtones. The quality of a sound depends on the number and relative amplitude of the overtones prent in the wave reaching the ear. |
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