The nature of language: A resume of recent work on the physics of speech and hearing

In introduction, the history of human language is outlined and the manner of speech production is briefly described with special reference to English. Following this is a summary treatment of available data on the subject of speech and hearing. Much of this is the result of investigations carried out during the last two or three years in the Research Laboratories of the Bell System at New York. Human speech employs frequencies from a little below 100 cycles per second to above 6000 cycles, a range of about six octaves. The ear can perceive sound waves ranging in pressure amplitude from less than 0.001 of a dyne to over 1000 dynes and in frequency of vibration from about 20 cycles per second to about 20,000, a range at about ten octaves. The intensities and frequencies used most in conversation are those located in the central part of the area of audition. The energy of speech is carried largely by frequencies below 1000, but the characteristics which make it intelligible, largely by frequencies above 1000. Under quiet conditions good understanding is possible with undistorted speech having an intensity anywhere from one hundred times greater, to a million times less than that at exit from the mouth. On the whole the sounds, th, f, s, and v are hardest to heat correctly and they account for over half the mistakes made in interpretation. Failure to perceive them correctly is principally due to their very weak energy although it is also to be noted that they have important components of very high frequency.