Have you ever heard audio engineers complain that a mix sounds "muddy"? Thankfully, this comment has nothing to do with actual dirt. Muddiness in a mixing can refer to many things, but in most cases, this quality can be chalked up to what is called frequency masking.

Frequency masking in audio is a fairly common issue that even the most competent audio engineers will struggle with at some point. Below, we'll uncover everything you need to know about this phenomenon and share several strategies to help you work through these challenges.

What Is Frequency Masking?

When two sounds occupy the same frequency range in a song, they can muffle each other, reducing clarity through a phenomenon called frequency masking. This is not to say that all sounds residing within the same frequency range are competing with one another; though frequency masking generally refers to the problematic, unwanted clashing of similar frequencies.

While frequency masking is somewhat common, it can be prevented with a trained ear and eradicated using tools like equalization as detailed below.

What Does Frequency Masking Sound Like?

The sound of frequency masking can vary based on where on the frequency spectrum the issue lies. Perhaps the best way to understand what frequency masking sounds like is to take two instruments with very similar sounds and layer them on top of one another. Notice how you can still hear both of the sounds, but you lose detail within each individual track.

Other audio engineers may describe frequency masking as muddled, muddy, or even boomy depending on where the masking issue is.

Listen to creator Streaky demonstrate how he chooses to clean up a muddy mix, showcasing the before and after across the frequency spectrum:

Where Is Masking Most Common Across the Frequency Spectrum?

It's much more common for masking to occur on the lower to mid range of the frequency spectrum, since these dense, long sound waves tend to take up a lot of territory. For this reason, it's common to see lower end sounds affixed to the center of a mix, without panning, or many effects beyond EQ and some forms of compression.

Common Points of Auditory Masking to Look Out For

In order to cut out auditory masking, you need to know what to listen for. Here are some common sound clash combinations that you're bound to experience while putting together a session:

Kick Drum and Bass

The kick drum and bass are two of the most important elements of the lower end of the frequency spectrum. With that in mind, these two pieces are bound to compete with one another. It's common to see techniques like sidechain compression and dynamic equalization to help balance out the relationship between this duo.

Guitar and Piano

Whether these instruments are playing chords or lead lines, they can quickly stifle each other unless catered carefully within the mid frequency range.

Vocals and Guitar

It's no surprise that the melodic instrument of guitar often competes with vocals, both primarily resting in the mid range of the frequency spectrum.

Synthesizers and Pads

These wide spanning sounds tend to find their home within the mid range of the frequency spectrum. Synthesizers and pads for this reason can easily compete with many sounds within your session.

7 Strategies to Stop Frequency Masking In Your Music

Masking occurs all across the frequency range, making it challenging to create genuine space in your productions. Here are a couple of strategies to stop frequency masking in your sessions:

Mindful Production

By far, the best way to stop frequency masking issues is to prevent overlapping frequencies before they become an issue. Take some time to learn about the general frequency range of each instrument and sound so that you can be better equipped to curate a balanced mix. For instance, you can use resources like this frequency guide provided by creator Producertech:

You can also employ simple strategies, like soloing or muting certain tracks temporarily to identify the source of the mud or frequency masking. From there, you can make an informed decision to either search for another sound, or adjust the competing tracks with the following processing methods to create space and clarity as needed:

Dynamic EQ

A dynamic EQ is unique in that it's reactive. Whereas a traditional equalizer is "set it and forget it" (thereby producing the same effect for the duration of a song), a dynamic EQ can shift according to the parameter of its environment.

For instance, you could set a dynamic EQ to cut out unnecessary bass frequencies to make room for the kick drum, but only when the kick hits so that you're not crushing the bass entirely.

You can also opt to boost certain frequencies when they tend to get lost in the mix, though this is typically done with high frequencies as opposed to low frequencies, if at all. The principle of spectral masking makes it so we are more likely to drown in lower frequencies versus higher ones, so tackle frequency masking techniques on the low end first and see how far you can get.

Sidechain Compression

Sidechain compression is a technique in which one signal is compressed according to the trigger of another. For example, let's say your kick drum and bass guitar are sharing some of the same frequencies. You could choose to sidechain the bass to the kick hits. This way, every time the kick comes in, the bass is compressed to provide needed space for the kick drum:

Frequency Carving

Sometimes, with all of your instruments playing, it can be difficult to determine which frequencies are muddying up your overall sound. It's possible that there are some points of extra resonance or problem areas that are leading to frequency masking. To start, try your best to identify the possible range in which the masking issues reside.

From there, solo out the tracks, until you narrow down which track or tracks are leading to unprofessional sound. You can use a sharp Q filter to listen in and identify the problem areas, lowering their volume and impact. Note that if you have to carve out frequencies at a level higher than about 3 decibels or so, it might be worth reconsidering the sound altogether:

Panning

Spreading out your mix across different points of the stereo field can help you uncover lost space, and build clarity in your session. It's best to focus on spreading out the higher frequencies though, since low frequencies can quickly muddle the wide range of your stereo field.

High Pass and Low Pass Filters

One of the easiest ways you can uncover space in your mix is by effectively using high pass and low pass filters. A high pass filter is used to cut out low frequencies while a low pass filter can be used to cut out high frequencies.

You'd be surprised, but instruments like the hi hat may contain a surprising amount of low end that can be quickly mitigated with a high pass filter. In the same breath, you may find that you bass brings unnecessary mid and high frequencies that can be adjusted with a low pass filter.

Bring Out a Balance

Remember that volume is also a significant tool when it comes to crafting a balanced, clean mix. You'll still want to prioritize cutting out unnecessary frequencies to prevent frequency masking, but don't forget to experiment with the level of the signals themselves. We often forget that the levels themselves are an integral part of putting together a mix.

Frequency Masking FAQs

Are you ready to fix masking in your mix? Use these commonly asked questions and answers to expand your understanding:

Why is frequency masking bad?

Frequency masking is undesired because it causes you to lose clarity and a professional sound in your mix. This issue is fairly common, but there are several preventable strategies and actionable solutions to fix frequency masking or preferably, avoid it altogether.

What is an example of a masking effect?

A masking effect occurs often when the bass and kick drum parts overlap in a mix, creating a muddled mix. You might struggle to hear mid or high range frequencies in the track, or feel as though the sound doesn't have professional clarity.

What is masking in music?

Masking occurs when the same frequency range is occupied by two or more tracks. This can cause the mix to sound clouded and potentially "muddy".

How do I prevent frequency masking?

You can prevent frequency masking by understanding where certain frequencies overlap and curating your mix accordingly. Fortunately, there are plenty of tools as outlined in this article to mitigate frequency overlap even if it's already present in your mix.

Paving your way to the final mix can be quite a process. Don't get discouraged while working to eliminate frequency masking from your session - this issue is naturally common, but nevertheless, the more you mix, the better suited you'll become at identifying and manipulating frequencies to your advantage. Have fun putting these session saving strategies to the test!