Digital Sound & Music: Concepts, Applications, & Science, Chapter 4, last updated 6/25/2013
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Figure 4.20 Potential acoustic gain, ( )
Increasing the PAG can be achieved by a number of means, including:
Moving the source closer to the microphone
Moving the loudspeaker farther from the microphone
Moving the loudspeaker closer to the listener.
It’s also possible to use directional microphones and loudspeakers or to apply filters or
equalization, although these methods do not yield the same level of success as physically moving
the various sound system components. These issues are illustrated in the interactive Flash
tutorial associated with this section.
Note that PAG is the “potential” gain. Not all aspects of the sound need to be amplified
by this much. The gain just gives you “room to play.” Faders in the mixer can still bring down
specific microphones or frequency bands in the signal. But the potential acoustic gain lets you
know how much louder than the natural sound you will be able to achieve.
The Flash tutorial associated with this section helps you to visualize how acoustic gain
works and what its consequences are.
4.2.2.2 Checking and Setting Sound Levels
One fundamental part of analyzing an acoustic space is checking sound levels at various
locations in the listening area. In the ideal situation, you want everything to sound similar at
various listening locations. A realistic goal is to have each listening location be within 6 dB of
the other locations. If you find locations that are outside that 6 dB range, you may need to
reposition some loudspeakers, add loudspeakers, or apply acoustic treatment to the room. With
the knowledge of decibels and acoustics that you gained in Section 1, you should have a better
understanding now of how this works.
There are two types of sound pressure level (SPL) meters for measuring sound levels in
the air. The most common is a dedicated handheld SPL meter like the one shown in Figure 4.21.
These meters have a built-in microphone and operate on battery power. They have been
specifically calibrated to convert the voltage level coming from the microphone into a value in
dBSPL.
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