Equal Loudness Contours

Equal loudness contours are  a graphical representation of perceived loudness of different frequencies at different volume levels.

equal loudness contours

Does that confuse you? First of all, loudness and volume have different definitions in this context. Loudness is subjective, volume is the objective measurement of the amplitude of sound (a more technical term is sound pressure level). The gist is that we subjectively perceive certain frequencies to be louder, even at the same volume as other frequencies. For example, a 40hz sine wave is perceived as being much quieter than a 1khz sine wave, even if the same amount of volume is being measured. Conversely, if we want a 40hz sine wave to sound as loud as a 1khz sine wave, we will need to add about 10db of gain to the 40hz sine wave to perceive it as the same loudness.

This phenomenon is mainly caused by the fact that our ear canals resonate at a range of 2khz-5khz. Notice the dips in the graph at that range, representing the most sensitive range of our hearing.

How does understanding this concept help us as musicians? The most important lesson here is that loudness affects how we perceive tone.

When we are shaping the tone of the guitar on an amp, we should be doing it at a level that’s similar to when we’ll be performing. What may sound good at “bedroom level” may reveal a bunch of problems (like too much highs or bass) at “gigging level”.

Another quick tip I’ve learned is that if a sounds is too “harsh” to the ears, then the likely culprit is the 2khz-5khz range where our hearing is most sensitive. Grab the EQ and do a little bit of reduction in that range to take the harshness out of the sound without sacrificing volume.

If you’re interested in these types of acoustic phenomenon, you might want to take a look into the field of psychoacoustics. Hope this was helpful!


How to Use EQ for Guitar

Equalizers are one of the most powerful yet misunderstood tools when it comes to building your guitar tone.  Often times, guitar players will twist and turn a knob without much understanding as to what it’s precisely doing to the signal. This can make for a tedious process of guessing and testing. Most of us just want to play with a satisfactory tone! Understanding the basics of equalization can go a long ways to minimize the time wasted.

The biggest misconception is using the equalizer as a creative tone shaping tool, as opposed to a corrective tool. Think about the word “equalizer” – the idea is to try and make the sound as equal to the original source as possible. In other words, it’s meant to correct the tendencies of the room, microphone, pickup, and amplifier that colour the guitar sound.

A concept that has helped me is the idea of subtractive equalization. The idea is to take away frequencies we don’t want to hear in our tone, as opposed to adding the ones we want to hear. Subtractive EQ is effective because we perceive it to be a less noticeable change than the opposite. Additive EQ has a tendency to add noise to a signal and can cause unwanted resonant frequencies in extreme cases. When shaping the guitar tone, think of what it could use less of, not more of.

Two common problem areas for guitarists are the low frequencies (<150hz) and the high frequencies (>4khz). Having too much low end will start to conflict with other bass instruments (bass guitar, kick drum) and too much highs will conflict with vocals and cymbals.  It’s important to understand that guitars are mainly a midrange (80hz-1.4khz) instrument and to be mindful of not occupying too much acoustic space beyond that range.

Start with the EQ dials set to a neutral 12 o’clock position. Make sure you’re playing at a moderate volume as this can affect how frequencies are heard (Fletcher-Munson curve). Then while playing a song with the rest of the band, adjust the bass and treble/presence knobs to a sweet spot where it doesn’t mask other instruments while providing a balanced tone. The mids dial can help to bring the guitar forward or back in the mix.

I’ve only scratched the surface when it comes to how powerful the equalizer tool can be. I hope I’ve inspired some of you to look deeper into this topic so that you can achieve a consistently musical tone in your performances. Good luck!