Tables 153-156 



TABLE 153. — Speech 



(Fletcher, Rev. Mod. Phys., 3, 258, 1931.) 



195 



Speech is composed of vowels and consonants. Most are continued in steady tones (con- 

 tinuants), long vowels, a, short, i, diphthongs, ou, semivowels, 1, fricative consonants, s; 

 others are interrupted (stops). The pure stops are p, t, ch, k; voiced, b, d, j, g. 



When frequencies, /, are measured in kilocycles, then the pitch P — log 2 F. J is the 

 intensity of the sound passing through a cm 2 of the wave-front. The intensity level 

 / = logio/ and is expressed in bells. 



TABLE 154. — Characteristic Resonance Values for Spoken Vowels 



The larynx generates a fundamental tone of a chosen pitch with some 20 partials, usually of low intensity. The 

 particular partial, or partials, most nearly in unison with the mouth cavity is greatly strengthened by resonance. Each 

 vowel, for a given mouth, is characterized by a particular fixed pitch, or pitches, of resonance corresponding to that 

 vowel's definite form of mouth cavity. These pitches may be judged by whispering the vowels. It is difficult to sing 

 vowels true above the corresponding pitches. The greater part of the energy or loudness of a vowel of a chosen pitch 

 is in those partials reinforced by resonance. The vowels may be divided into two classes, — the first having one char- 

 acteristic resonance region, the second, two. The representative pitches of maximum resonance of a mouth cavity 

 for selected vowels in each group are given in the following table. 



Vowel indicated by italics in 

 the words. 



Pitch of maxi- 

 mum resonance. 



Vowel indicated by italics in 

 the words. 



Pitch of maxi- 

 mum resonance. 



father, far, g!<ard 



raw, fall, hawl. 



no, rode, goal., 



gloom, move, group 



gio 

 732 

 461 

 326 



mat, add, cat .... 



pet, feather, bless . . . 



they, bait, hate. . . 



bee, pique, machine 



800 and 1840 

 691 and 1953 

 488 and 2461 

 308 and 3100 



Pitch in octaves from one kilocycle. For the first 6 vowels high pitch region less 

 intense (Fletcher). 



TABLE 155. — Speech Power (Fletcher) 



Average conversational speech power, 10 microwatts or 100 ergs per second. About 1/3 

 of time no sound is flowing (pauses), so if silent intervals are excluded these values may 

 be taken as 15 and 150. Shouting as loud as possible increases 100-fold, whispering in- 

 telligibly 1/10,000. The mean speech power may be defined as average over 1/100 sec. 

 period ; phonetic speech pozver, max. value of mean speech power of a fundamental vowel 

 or consonant ; peak speech pozver, max. value of instantaneous power over interval 

 considered. 



TABLE 156. — Phonetic Powers, Average Conversation 



The most powerful sound is " awl" — 900 times the power of th in thigh. Intoned 

 without emphasis it is about 50 microvolts. Peak powers are 10-20 times the phonetic 

 power. In ordinary conversation 2% of time > 20 db over average level ; 42%, 6 to 16 db. 



Note. — For Bibliography of Acoustics of Buildings (Watson) see Nat. Res. Council, 

 Reprint, and Circulars, No. 98, 1931, or Journ. Acoust. Soc. Amer., 2, 14, 1931. 



Smithsonian Tables 



