Audio Engineering

Measurement 79

would be a 24-dB difference in level between these two loudspeakers when fed by the
same signal. Some consumer market loudspeakers vary this much in effi ciency.

2.28 Summary

The decibel is the product of the greatest engineering minds in communications early in
the last century. When it is combined with the work of Oliver Heaviside and others on
impedance at the turn of the 20th century, we are equipped to handle audio levels. The
concepts of dB, Z, and dBm are the tools of the professional as well as their language.

Further Reading .......................................................................................................

Albers , V. M. , ‘ The world of sound ’ , New York : Barnes , 1970.

Jay , F. (Ed.), ‘IEEE standard dictionary of electrical and electronics terms’ , 2nd ed. ,
New York : The Institute of Electrical and Electronics Engineers , 1977.

Keast , D. N. , ‘ Measurement in mechanical dynamics ’ , New York : McGraw-Hill , 1967.

Read , O. , ‘ The recording and reproduction of sound ’ , Indianapolis, IN : Howard W. Sams ,
1952.

Research Council of the Academy of Motion Picture Arts and Sciences , ‘ Motion picture
sound engineering ’ , New York : Van Nostrand , 1938.

Wood , A. , ‘ The physics of music ’ , New York : Dover , 1966.