6:5/ Neural Mechanisms of Hearing 1 17 



5. Summary of Hearing 



Biophysical approaches to the sensation of hearing have been discussed 

 in Chapters 1 and 3 as well as in this one. The material in Chapter 1 

 dealt with the physical parameters of sound important for hearing and 

 with the anatomical characteristics of the ear, both on a gross level and 

 also as revealed by histology. All of these are very important parts of 

 man's knowledge of hearing. These topics in Chapter 1 are all well 

 known and have been firmly established for many years. Although 

 detailed studies may slightly modify them, the contents of Chapter 1 

 probably will not be dramatically altered. Certain peripheral studies, 

 such as those of the mechanical behavior of the eardrum and ossicles 

 at higher sound pressure levels, will undoubtedly supplement the present 

 picture of the physical properties of the anatomical structure of the ear. 



The ideas presented in Chapter 3 on the uses of pulses of sound for 

 echo-location by bats, porpoises, and birds are of more recent origin. 

 The first significant studies in this direction date back only to 1940. 

 Nonetheless, the ideas presented there are all so well supported by 

 experimental evidence that it appears unlikely that they will be signifi- 

 cantly altered in the near future. It does seem more probable that 

 echo-location will be recognized as an important factor in other species. 



The material in this chapter deals with the most important bio- 

 physical aspects of hearing, namely the conversion of sound waves to 

 neural impulses and their analysis within the central nervous system. 

 Although these topics are central to the biophysics of hearing, large 

 gaps still remain in our understanding. Basically, the uncertainties are 

 similar to those discussed in Chapter 5. It is in this general area that 

 significant, major advances may be anticipated. 



REFERENCES 



1. Wever, E. G., and Merle Lawrence, Physiological Acoustics (Princeton, 

 New Jersey: Princeton University Press, 1954). 



2. von Bekesy, Georg, and W. A. Rosenblith, "The Mechanical Properties of 

 the Ear," in Handbook of Experimental Psychology, S. S. Stevens, ed., (New 

 York: John Wiley & Sons, Inc., 1951) pp. 1075-1115. 



3. Articles in J. Acous. Soc. Am. by Georg von Bekesy pertinent to this chapter 

 include : 



a. 1949, 21, pp. 233-245. "The Vibration of the Cochlear Partition 

 in Anatomical Preparations and in Models of the Inner Ear." 



b. 1949, 21, pp. 245-254. "On the Resonance Curve and Decay 

 Period at Various Points on the Cochlear Partition." 



c. 1953, 25, 770-785. "Description of Some Mechanical Properties of 

 the Organ of Corti." 



