There are a few very basic reference materials that every audio engineer should know about.

Here are a few of them:

Frequency Chart

1. Frequency Charts

This type of chart shows the frequency range of some common instruments. Ever wonder how far you can go with a low-pass filter EQ? Look up what instruments are in your track, and this can help you ballpark.

Pretty sure that you want to boost a certain instrument, but not sure where to start?

You can use this for reference.  Trying to figure out from where some of the muddiness in your mix is stemming?  Reference this chart and look for overlaps among other things.  It’s so basic, but so useful.  I particularly love the interactive chart made available by, which is also available for sale as a poster here.

Equal Loudness Curve

2.  Equal Loudness Curve

Awareness of this chart is important because it tells you a lot about the way we perceive sound as human beings.  Different frequencies at varying loudnesses are perceived differently by the human ear.  This chart shows you the actual loudness points at each frequency that will be perceived as equal volume by the human ear.

This chart helps engineers conceptualize why the frequency balance of a mix will sound different at different volumes.

It’s an essential concept to understand for any mixing engineer that wants to accurately monitor their mix.

Polarity Patterns

3.  Microphone Polarity Patterns

Different polarity patterns affect the sound you will ultimately get.  So it’s important to be aware of what polarity pattern your microphone is currently using.  I could write pages about polarity patterns and their importance, and potentially bore some of you to death.  So instead, I’ll just post this Sound on Sound article here, so that those of you that are interested can read more.

Microphone Types

4.  Microphone Types

Microphones detect the physical energy that creates sounds in the air, and convert it to electrical energy in the form of a voltage or a current.  There are many ways to go about this conversion, so there are many types of microphones out there.

For musical purposes, you can explore the most commonly used microphones using the interactive graph on Georgia State University’s website.

If you want to get really nerdy about it though, search some of the alternative microphone types – liquid microphones that involve free flowing water are some of my favorite.

5.  Reflection Coefficients and Acoustics

Different materials reflect more sound than others, and it’s important to understand how your surroundings will affect your sound.  The scientific way to understand this is to look at the reflection coefficient for varying materials.

It’s great to have a chart like this one (on the SAE Institute website) that shows how a range of materials will reflect different frequencies of sound.

As an audio engineer, I don’t have much use for the actual reflection coefficients; I don’t plug them into formulas very often, if ever.  However, this type of chart is something that I reference on occasion to spruce up my working knowledge of how different materials reflect sound in a relative sense.  Inversely, you could also spruce up your knowledge with an absorption coefficient chart.