Sound Advice: Sound Pressure Level (SPL) and the Decibel

SPL Meter

In the last Sound Advice article, we discussed the proper techniques in using the channel faders and the master fader.  Using the previous few articles should now have you properly mixing several channels to the master output of your audio mixer, with the main output meter calibrated to the ideal SPL for your venue, and the fader positions well balanced across the mixer’s panel.  If you were a little confused on SPL and what the proper SPL should be, then don’t worry.  Let’s take a brief break from our mix assignment and discuss SPL and decibels.

What is SPL?

Sound Pressure Level, or SPL, is a measure of the acoustic pressure of the sound in a particular space.  Simply stated, it is the apparent volume of the sound present in the space as measured on a sound pressure level meter.  The units of the measurement are in decibels (dB’s) and have a reference to atmospheric pressure (but that’s not really important).  What is important for you to know is that SPL measurements are critical in properly calibrating a sound system within a venue.  Why?  For one, we want to know that when our audio mixer reads 0 dB on the output meter, that equals our targeted SPL in the room.  Then, we realistically know at all times our relative volume by observing the output meters.  So, let’s dive into SPL…

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