488 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 1924 



speech sounds. Since only a limited range and variety of sounds 

 can be spoken, it is natural that there should be many similarities 

 betAveen the speech sounds of different languages. The elementary 

 sounds of a given tongue are combined into syllables and words, and 

 these in turn joined together into phrases to convey ideas, all accord- 

 ing to the mutual conventions of the people who use the language. 



The voice alone enabled man to communicate under circumstances 

 Avhere his gestures could not be seen and at distances beyond where 

 his facial expression could be made out. In our own times the in- 

 \ention and development of the telephone has marked a new step 

 in the evolution of human society, extending the vocal range of man 

 to extraordinary degrees. Voices are hourly carried with instant 

 speed from one end of the land to the other and it is now possible 

 for a speaker to address at one time a million persons gathered about 

 him or scattered at distant points. Speech is the load Avhich the 

 telephone system transports, and the ear is the consumer of the 

 product. Alexander Graham Bell, inventor of the telephone, as 

 student and professor of vocal physiology gained a deep insight 

 into the mechanism of operation of the voice and ear before his 

 greatest invention was made. Throughout his life he devoted him- 

 self to the alleviation of the infirmities of the deaf and the dumb. 

 Interest in the problems of speech and hearing comes naturally, 

 therefore, to the telephone organizations which bear his name by 

 sentiment as well as by the needs of their practice. 



This paper refers briefly to the mechanism of speech and hearing 

 and then describes some of the physical data of oral communication 

 which have been obtained by investigations carried on during the 

 past few years, A selected bibliography of published papers is at- 

 tached. Much of the material brought together and summarized 

 here has appeared in scattered form in the articles referred to. 



The organs of speech are the lungs, which by their bellows-like 

 action function as a motor element to supply streams of air which 

 pass in and out through the vocal passages. The vocal cords, the 

 tongue and lips, and the cavities of the mouth, nose, and throat, 

 impress on the air flow variations which are heard as sounds. The 

 vocal cords are a pair of muscular ledges on opposite sides of the 

 larynx which can be stretched and brought together, forming be- 

 tween them a slit of adjustable width through which the breath 

 passes. The opening between the vocal cords is called the glottis. 

 The flow of the breath is modulated to form the sounds of speech 

 by the vibration of the vocal cords and by the resonant reenforce- 

 ment of the vocal cavities. 



Speech is composed of letter sounds usually divided into vowels 

 and consonants, and those ordinarily used in the English language 

 are tabulated in Figure 1. So far as possible the sounds are ex- 



