Page 51 - Master Handbook of Acoustics

TABLE 2-3 Reference Quantities in Common Use

TABLE 2-4 Prefixes, Symbols, and Exponents

Acoustic Power

It doesn’t take many watts of acoustic power to produce very loud sounds. This is fortunate for music
playback because loudspeaker efficiency (output for a given input) is very low, perhaps on the order
of 10%. On the other hand, increasing amplifier power to achieve higher acoustic levels can be

frustrating. Doubling amplifier power from 1 to 2 W is a 3-dB increase in power level (10 log 2 =
3.01), but this yields a very small increase in loudness. Similarly, an increase in amplifier power
from 100 to 200 W or 1,000 to 2,000 W yields the same 3-dB increase in level.
Table 2-5 lists sound pressure and sound-pressure levels of various sounds. There is a vast
difference in sound pressure from 0.00002 Pa (20 μPa) to 100,000 Pa, but this range is reduced to a
convenient form when expressed in sound levels. The same information is present in graphical form

in Fig. 2-2.