A Discussion on the 'Ear' Under Water || Some Aspects of Mammalian Hearing under Water

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<ul><li><p>Some Aspects of Mammalian Hearing under WaterAuthor(s): F. W. Reysenbach De HaanSource: Proceedings of the Royal Society of London. Series B, Biological Sciences, Vol. 152, No.946, A Discussion on the 'Ear' Under Water (Apr. 26, 1960), pp. 54-62Published by: The Royal SocietyStable URL: http://www.jstor.org/stable/75363 .Accessed: 07/05/2014 14:52</p><p>Your use of the JSTOR archive indicates your acceptance of the Terms &amp; Conditions of Use, available at .http://www.jstor.org/page/info/about/policies/terms.jsp</p><p> .JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range ofcontent in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new formsof scholarship. For more information about JSTOR, please contact support@jstor.org.</p><p> .</p><p>The Royal Society is collaborating with JSTOR to digitize, preserve and extend access to Proceedings of theRoyal Society of London. Series B, Biological Sciences.</p><p>http://www.jstor.org </p><p>This content downloaded from 169.229.32.136 on Wed, 7 May 2014 14:52:01 PMAll use subject to JSTOR Terms and Conditions</p><p>http://www.jstor.org/action/showPublisher?publisherCode=rslhttp://www.jstor.org/stable/75363?origin=JSTOR-pdfhttp://www.jstor.org/page/info/about/policies/terms.jsphttp://www.jstor.org/page/info/about/policies/terms.jsp</p></li><li><p>S. Dijkgraaf (Discussion Meeting) S. Dijkgraaf (Discussion Meeting) with the swimbladder, is exclusively or better developed in the male. In other cases the sounds are only produced during mating or breeding activities. When such sounds were played back to silent fishes of the same species, a general activity increase and sometimes a positive approach towards the sound source (at close </p><p>range) or towards fellow fishes was observed (Tavolga I958). In other cases the sound had obviously a threat function (Dijkgraaf 1947b). There are certainly many other possibilities like guarding the nest, defence of territory, and perhaps even echo-location (Griffin I958). More evidence is urgently needed, particularly with </p><p>respect to the biological significance of hearing in freshwater fishes. </p><p>REFERENCES (Dijkgraaf) </p><p>Dijkgraaf, S. I947a Experientia, 3, 206-208. Dijkgraaf, S. 1947b Experientia, 3, 493-494. Dijkgraaf, S. I950 Physiol. comp. Oecol. 2, 81-106. Dijkgraaf, S. I952a Z. vergl. Physiol. 34, 104-122. Dijkgraaf, S. I952b Experientia, 8, 205-216. Dijkgraaf, S. &amp; Verheijen, F. J. 1950 Z. vergl. Physiol. 32, 248-256. Fish, M. P. I954 Bull. Bingham Oceanogr. Coll. 14, 3-109. Frisch, K. v. I936 Biol. Rev. 11, 210-246. Frisch, K. v. 1938 Z. vergl. Physiol. 25, 703-747. Frisch, K. v. &amp; Dijkgraaf, S. I935 Z. vergl. Physiol. 22, 641-655. Griffin, D. R. I958 Listening in the dark. New Haven. Poggendorf, D. I952 Z. vergl. Physiol. 34, 222-257. Pumphrey, R. J. I950 Symp. Soc. Exper. Biol. 4, 3-18. Reinhardt, F. I935 Z. vergl. Physiol. 22, 570-603. Schneider, H. I94I Z. vergl. Physiol. 29, 172-194. Sch6ne, H. 1959 Ergebn. Biol. 21, 161-209. Suckling, E. E. &amp; Suckling, J. A. I950 J. gen. Physiol. 34, 1-8. Tavolga, W. N. I958 Physiol. Zool. 31, 259-271. Wohlfahrt, T. A. I939 Z. vergl. Physiol. 26, 570-604. Wohlfahrt, T. A. 1950 Z. vergl. Physiol. 32, 151-175. </p><p>Some aspects of mammalian hearing under water </p><p>By F. W. REYSENBACH DE HAAN </p><p>Eindhoven, Holland </p><p>In all probability the first, most primitive life must have had its origin in the water. When one tries to form an idea of the development of 'hearing under water', it is understandable that the formation of an adequate sensory apparatus for hearing depends on the development of the tactile sense, and later on the coming into </p><p>being of a nervous system, lateral line organ, and finally on the formation of the stato-acoustic end-organs of the labyrinth. This gives little cause for wonder, as the reaction toOpressure waves must have been an early felt biological necessity. The step from pressure waves under water to sound waves of very low frequency is neither a great nor a fundamental step; it is merely the addition of sound modality to vibration. </p><p>with the swimbladder, is exclusively or better developed in the male. In other cases the sounds are only produced during mating or breeding activities. When such sounds were played back to silent fishes of the same species, a general activity increase and sometimes a positive approach towards the sound source (at close </p><p>range) or towards fellow fishes was observed (Tavolga I958). In other cases the sound had obviously a threat function (Dijkgraaf 1947b). There are certainly many other possibilities like guarding the nest, defence of territory, and perhaps even echo-location (Griffin I958). More evidence is urgently needed, particularly with </p><p>respect to the biological significance of hearing in freshwater fishes. </p><p>REFERENCES (Dijkgraaf) </p><p>Dijkgraaf, S. I947a Experientia, 3, 206-208. Dijkgraaf, S. 1947b Experientia, 3, 493-494. Dijkgraaf, S. I950 Physiol. comp. Oecol. 2, 81-106. Dijkgraaf, S. I952a Z. vergl. Physiol. 34, 104-122. Dijkgraaf, S. I952b Experientia, 8, 205-216. Dijkgraaf, S. &amp; Verheijen, F. J. 1950 Z. vergl. Physiol. 32, 248-256. Fish, M. P. I954 Bull. Bingham Oceanogr. Coll. 14, 3-109. Frisch, K. v. I936 Biol. Rev. 11, 210-246. Frisch, K. v. 1938 Z. vergl. Physiol. 25, 703-747. Frisch, K. v. &amp; Dijkgraaf, S. I935 Z. vergl. Physiol. 22, 641-655. Griffin, D. R. I958 Listening in the dark. New Haven. Poggendorf, D. I952 Z. vergl. Physiol. 34, 222-257. Pumphrey, R. J. I950 Symp. Soc. Exper. Biol. 4, 3-18. Reinhardt, F. I935 Z. vergl. Physiol. 22, 570-603. Schneider, H. I94I Z. vergl. Physiol. 29, 172-194. Sch6ne, H. 1959 Ergebn. Biol. 21, 161-209. Suckling, E. E. &amp; Suckling, J. A. I950 J. gen. Physiol. 34, 1-8. Tavolga, W. N. I958 Physiol. Zool. 31, 259-271. Wohlfahrt, T. A. I939 Z. vergl. Physiol. 26, 570-604. Wohlfahrt, T. A. 1950 Z. vergl. Physiol. 32, 151-175. </p><p>Some aspects of mammalian hearing under water </p><p>By F. W. REYSENBACH DE HAAN </p><p>Eindhoven, Holland </p><p>In all probability the first, most primitive life must have had its origin in the water. When one tries to form an idea of the development of 'hearing under water', it is understandable that the formation of an adequate sensory apparatus for hearing depends on the development of the tactile sense, and later on the coming into </p><p>being of a nervous system, lateral line organ, and finally on the formation of the stato-acoustic end-organs of the labyrinth. This gives little cause for wonder, as the reaction toOpressure waves must have been an early felt biological necessity. The step from pressure waves under water to sound waves of very low frequency is neither a great nor a fundamental step; it is merely the addition of sound modality to vibration. </p><p>54 54 </p><p>This content downloaded from 169.229.32.136 on Wed, 7 May 2014 14:52:01 PMAll use subject to JSTOR Terms and Conditions</p><p>http://www.jstor.org/page/info/about/policies/terms.jsp</p></li><li><p>Some aspects of mammalian hearing under water </p><p>Before, in a remote past, dramatic geological changes had created the conditions for the development of life on land and therefore also for life in the air, the fishes were the most highly developed vertebrates. They probably possessed a hearing organ entirely adapted and adjusted to hearing under water. We assume that some of these animals possessed the potency to answer with success the tremendous demands made by the transition to land life. Under-water hearing was transmuted into air-hearing. Air-hearing finally reached its highest degree of development in the mammals. </p><p>However interesting this development may be, it lies outside the scope of this lecture. We wish only to call your attention to the behaviour of mammalian </p><p>hearing, which is air-hearing par excellence, when it has to function under water. Which ways had nature to follow to readapt this kind of hearing with optimal </p><p>results to the second change of environment? Was it a regression or a new step forward? </p><p>It is known that there exists a series of mammalian species which have found their way back to aquatic life. These animals lead a life which is partially or entirely readapted to the water. In order to save time while still giving you a reasonable idea of some aspects of mammalian hearing under water, I propose to discuss only the possibilities of two mammalian hearing organs, one which is not at all, and another which is entirely adapted to hearing in this medium: on the one hand the </p><p>hearing of man, on the other that of the toothed whale. </p><p>Before we enter in detail into these problems, a few essential questions must be answered: </p><p>(1) What is sound? </p><p>(2) What is the biological significance of sound? Sound is a periodic compression and rarefaction of the medium in which it is </p><p>produced, transmitting itself with a speed dependent on this medium, and which, from the biological point of view, may result in an acoustic sensation. We therefore </p><p>speak of the sound wave, the sound frequency or pitch, the speed of sound and the intensity of sound. </p><p>The mutual relationship between the first three is indicated by the equation </p><p>A = v/v </p><p>The wavelength of sound A is equal to the speed of sound v divided by the </p><p>frequency v. The higher the frequency, the shorter the wavelength and the more the waves are bundled and obtain the nature of rays, as is the case with light. According to the above definition, the wavelength is, however, also dependent on the speed of sound, which in turn depends on the medium. In the air this </p><p>velocity is about 300 m/s, in sea water 1200 m/s, or four times greater. A sound wave of the same frequency is therefore four times as long in water as in air. This </p><p>implies that in water the bundle of ray character can only occur with much higher frequencies, and this is again decisive for the degree of directional power of sound. </p><p>Finally, it is of interest to know that as the frequency of the sound becomes </p><p>higher, its power of penetration decreases: the long waves of the low frequencies </p><p>55 </p><p>This content downloaded from 169.229.32.136 on Wed, 7 May 2014 14:52:01 PMAll use subject to JSTOR Terms and Conditions</p><p>http://www.jstor.org/page/info/about/policies/terms.jsp</p></li><li><p>F. W. Reysenbach de Haan (Discussion Meeting) </p><p>penetrate very far in all directions, the very short waves of supersonic frequencies radiate as a bundle in one direction, but do not reach far. They are absorbed in the medium to a much greater extent than the longer waves. </p><p>The most important biological significance of sound is the information given by it. This information is directly dependent on its directional nature. Only then follow the penetrative power, the intensity, and the emitted or subsequently reflected frequency spectrum and the variation of sound in time. </p><p>What use can the hearing organ make of these data ? Its function is to offer the sound waves it receives to the sensory epithelium of the inner ear with the least possible loss. This is the task of the reception and transmission apparatus of the external ear and middle ear, which is essentially a mechanical transmission system for bringing about the transition of sound from one medium into another, without loss and distortion, and for each of the two ears separately. </p><p>The hearing organ must be able to determine as quickly and faultlessly as possible the direction and nature of the sound. The determination of direction mainly depends on the external ear and the shortest distance in the sound-transmitting medium between the two independently working ears (compare, for example, with binocular vision), and on the architecture of the central nervous pathways for sound and their correlation. </p><p>The nature of the sound is determined by a frequency-analysis in the greatest possible detail, that is by an inner ear as finely differentiated as possible. </p><p>A comparison with the eye shows that this effectively works over a much smaller distance than the ear, because its receptive field is limited by optical obstacles which would not affect the propagation of sound. The eye is, moreover, dependent on the presence of sunlight or derivatives of it. The olfactory sense depends to a high extent on prevailing conditions such as direction of wind or degree of humidity. The tactile sense does not serve any purposes of telereception, apart from the lateral line organ of the fishes. For the mammals the ear remains the telereceptor par excellence. It gives information first and most rapidly, and is therefore the most efficient warning organ. </p><p>What is to be expected of the auditory function in man when he is to hear under water ? The external ear has then lost its function; for sound it is physically identical to water. The middle ear will no longer be able to display its function. When sound is transmitted from the water medium to the air medium, 99-9 %, or more than 60 db, is lost. An even more important feature is that underwater sound- we are speaking here of the lower frequencies-causes a vibration of the whole skull including the two hearing organs, and not of the two middle ears separately with respect to inner ear and skull, as is the case in air. </p><p>This leads us to expect: (1) That a loss of sound-intensity must arise as occurs in human subjects with an eliminated middle ear as a result of chronic otitis media or a radical operation, a loss of hearing, therefore, of about 60 db, (2) that there can be no question of a directional-sensation in hearing under water. </p><p>I have been in the position to make audiograms of myself and other test subjects under water; these confirmed that the loss of intensity was indeed 60 db. </p><p>56 </p><p>This content downloaded from 169.229.32.136 on Wed, 7 May 2014 14:52:01 PMAll use subject to JSTOR Terms and Conditions</p><p>http://www.jstor.org/page/info/about/policies/terms.jsp</p></li><li><p>Some aspects of mammalian hearing under water </p><p>Determination of direction proved entirely impossible. Neither the distance between observer and source of sound, nor the type of sound, namely short pulses or sweep tones, made any difference. In these experiments the frequency range of 1000 to 16000 c/s was investigated (Reysenbach de Haan 1956). About a year later Hamilton, in the U.S.A., who did not know of our investigation, carried out more or less the same experiments and arrived at the same results and conclusions. </p><p>Whales and dolphins are the mammals most adapted to submarine life, also with regard to their sense organs. This implies a regression of the visual sense and the almost total disappearance of their olfactory sense, and has been substituted </p><p>by a very particular development of the auditory sense. This is illustrated by the ear of a toothed whale, for example, the pilot whale, and of the common porpoise. The external ear is absent. In view of what was said above, this should be regarded as a very understandable adaptation. Under water a pinna would be without function as a sound receiver, and would moreover be in conflict with the stream- lined form. The auditory opening in the skin...</p></li></ul>

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