382 BELL SYSTEM TECHNICAL JOURNAL 



(f) Hainnier 



Length, .8 to .9 cm. 

 Weight, 23 mg. 



id) Anvil 



W'l-i.nht, '2.') mg. 



(e) Stirrup 



Weight, 3 mg. 



(/) Mechanical Impedance of the Ear Drimi 



(Data by Wcgel and Lane. \M\ Telephone Laboratories) 



The order of magnitude is 20 to 30 mechanical ohms (cgs units) 

 over the frequency range from 200 to 4,000 dv. 



XIL Si'i;i:(H Knkkc.y 



.1. .Speech i'ower 



(Data furnished by C. F. -Sacia and L. J. Si\ian, Bell Telephone 

 Laboratories) 



L The average speech power delivered b\- an average speaker is 

 about 10 microwatts. In the process of obtaining the average the 

 silent intervals were included. If they are excluded the average 

 increases about .50'^;. The peak power frequently rises to 2,000 

 microwatts. 



2. \'ariation of average speech i)ii\\tT (leli\ere(l by dilTerenl persons 

 during conversation. (Fig. ().) 



B. Energy Freciuency Distrii)Uti(m of .\\eragc Speech 



(Crandall and MacKcnzie, Phys. Rn\. 19. p. 221, ^Llrch, 1922) 



(Fig. 7) 



C. Acoustic I'ower in \\)wel Sounds 



(Data furnished by (". F. Sacia of the Hell Telephdne l.abciratorics. 



This data together with a description of the ai)par,itus .ind 



methods usi-d in nbl, lining it will be given in a pajier soon to be 



published. ) 



Table III I'ontains data on the power of indixidual xowels obtained 

 from analyzing the vowel portions of the syllables shown in the key- 

 word. The first two columns give the average power in microwatts 



