ARCHITECTURAL ACOUSTICS 119 



of construction must be chosen so that the time of reverberation 

 calculated by Sabine's formula will be within the limits regarded 

 as satisfactory under the conditions which will ordinarily pre- 

 vail ill the auditorium. 



In the case of buildings already constructed excessive 

 reverberation can be reduced by the introduction of suitable 

 absorbent material. Echoes, including sound foci, can be 

 eliminated by determining the surfaces responsible for their 

 production and altering these or preventing the sound by suit- 

 able absorbent sheets from striking them. 



The problem of acoustic isolation has also been scientifically 

 investigated, but here the information is less complete than 

 for the satisfactory design of auditoriums. 



1. Roger-Smith, T., Acoustics in Relation to Architecture and Building. 



2. Sabine, W. C, Engineering Record, Ixi, pp. 779-81, 1910. 



3. Watson, F. R., Engineering Record, Ixvii, p. 265, 191 3. 



4. Sabine, W. C, Engineering Record, i, 1900 ; also in American Architect, 



Ixviii, 1900. 



5. Sabine, W. C, The Brickhiiilder , xxiii, pp. 1-6, 1914. 



6. Franklin, W. S., Physical Review, xvi, pp. 372-4, 1903. 



7. Jager, S., Sitzungsberichten der Kaiserl. Akad. der Wissenschaften in 



Wien Matem.-naturw. Klasse, bd. cxx, abt. iia, Mai 1911. 



8. Sabine, W. C, Proc. Amer. Acad, of Arts and Sciences, xlii, 2 June igo6. 



9. Taylor, H. O., Physical Review, ii (2), p. 270, 1913. 



10. Watson, F. R., Bulletin 87 of the University of Illinois Engineering 



Experimental Station, 1916. 



11. Tallant, Hugh, The Brickbuilder, xxii, p. 169, 1913. 



12. Sabine, W. C, American Architect, civ, pp. 257, 279, 1913. 



13. Raman, C. V., and Sutherland, G. A., Proc. Roy. Soc, A., vol. C, 1922. 



14. Tallant, Hugh, The Brickbuilder, xxii, p. 225, 1913. 



15. Sabine, W. C, The Brickbuilder, xxiv, pp. 31-6, 1915. 



16. Sabine, P. E., American Architect, cxviii, pp. 102-8, 1920 ; cxx, pp. 



215, 266, 1921. 



17. Watson, F. R., Bulletin 127 of the University of Illinois Engineering 



Experimental Station. 



18. Michel Eugen, Horsamkeit Grosser Rdume, F. Vieweg & Sohn, Braun- 



schweig, 192 1 : a r6sum6 of the subject which the writer has not 

 yet had the opportunity of consulting. 



