How Does A High-pass Filter Sound?

When mixing or mastering audio, one needs to understand how to treat musical elements.

EQ or equalization is a huge part of audio production and this post I’m going to explain how a high pass filter sounds like.

This is important to know because many times words or terms like low pass and high pass filters are usually used in audio production.

They all serve their purposes and this post will partly discuss that. If you’re not an audiophile that needs a deep explanation, not to worry, I’ll keep this post brief.

So, how does a high-pass filter sound?

A high pass filter makes audio sound lighter due to the fact that it filters out low or bass frequencies. Depending on how a high pass filter is used, it can make audio sound like the output of a small radio or telephone with no sub or low frequencies. Audio can also sound cleaner with no low energy build up when a high-pass filter is used and applied in moderation.

Low energy

A lot of muddy frequencies get caught in the low end frequency area of an audio signal. The fact  is, most instruments give off low end energy that is inaudible to the human ear but is nevertheless present.

For a human being, we can only hear low frequencies of 20Hz which means that anything below that is not audible to our ears.

However, even low frequencies that are close to or around 20Hz are not pretty easy to hear.

But once you do catch them with your ears, you can easily notice that low energy.

This low energy can be an issue in audio production because what we generally strive for is absolute quality paired with immense clarity.

Low end energy that get trapped in the low frequency spectrum of audio can make a mix sound muddy which in turn can make a mix lack the necessary clarity.

To avoid issues of clarity and to ensure that we don’t have any frequencies making it hard for other frequencies to pass through and be heard, we therefore use what is known as a high pass filter.

A high pass filter simply filters away low frequencies that are not needed.

The usual case in audio production is filtering out any frequencies below 20Hz because no human being will hear them anyway.

HPF for effect

The main use of a high pass filter or HPF is audio mixing is to filter out the nasty low frequencies that can easily muddy up a mix.

However, high pass filters are also used simply for effect

In recent years, the use of low and high pass filters to create an effect is something that has become a huge part of music production.

For example, Drake is known for his use of low pass filters on beats and instrumentals to create a sort of down tone underwater effect to make his vocals pop and feel mellow.

Many musicians especially in genres like EDM are known to use high pass filters at certain sections of their songs to slowly build up to the climax or what is commonly known as the “drop” of the song.

With that said, a high pass filter when excessively applied will generally sound like a small radio with no sub or low frequencies and in other instances a high pass filter on vocals may sound like a voice on a telephone. This effect is sometimes utilized in motion picture to simulate or mimic phone conversations.

Low Pass filters LPF

Low Pass filters are generally the opposite of high pass filters.

They essentially filter or block out high frequencies which sort of muffles the sound of audio being run through the LPF.

There are useful in controlling any frequencies above the human hearing threshold which is 20,000 Hz or simply 20 Khz.

Like I’ve already said, Low Pass filters are also used for effect in that they are mostly used to simulate what most people refer to as the underwater effect.

The underwater effect is what happens when high frequencies in am audio signal are filtered out or not let through.

When to use a high pass filter

A high pass filter is something that can be quite useful when you’re dealing with any mixes that have too much low end energy.

Filtering out any unwanted frequencies can help you retain the frequencies that you need without them being completely drowned out by the low end.

Bass heavy records are something that you have to pay attention to when mixing because some bass elements tend to have a lot of low frequency information that is uneeded and simply gets in the way of other sounds in the mix.

Furthermore, you can also apply a high pass filter to any mid to high frequency sounds that have low end information that could end up obstructing your low frequency sounds such as bass.

When to use a low pass filter

A low pass filter can be used in the exact opposite way that a high pass filter is used.

If you sense that a mix has a lot of high frequency energy that makes it difficult for you to hear a clear mix, applying a slight low pass filter can be helpful.

Low Pass filters can also be used to filter out unneeded mid to high frequency information in bass instruments that are meant to only impact the low end of a track.