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Podcast Production
11
min
September 14, 2023

What is audio compression? A guide for podcasters

Have you ever noticed how the volume fluctuates during your podcast recordings? One moment you’re leaned back in the chair whispering and the next moment your roaring with laughter on the microphone. 

The result? Your listeners constantly adjust their volume, making for a terrible listening experience. 

You want your podcast to have an even volume balance, and that’s where compression comes in. 

In this post you’ll learn everything you need to know to achieve an even balance to your podcast’s mix. 

What we’ll cover

What is audio compression?

Audio compression is a process used to reduce the loud parts of an audio track and increase the quiet parts to create a more even volume across the track. 

Audio compression evens out the dynamic range, or the difference between loudest and quietest parts of any recorded audio. 

By equalizing the loud and quiet elements of the mix, both can be heard more clearly. Compression creates the  overall balance you need for a professional sound. 

Why is compression important for podcasters?

Compression helps podcasts sound professional and avoid listener drop-off for several reasons. 

  1. Compression improves the clarity of your audio by ensuring that even the quieter parts are still audible.
  2. Compression maintains consistency across episodes to ensure your audience has a professional and enjoyable listening experience.  
  3. Compression prevents ear fatigue by keeping the audio levels consistent. 

Compression is essential, but it should be used sparingly and lightly so as not to destroy the natural dynamics of your voice. But how do you do that? We’ll dive into the details in a bit. But first, we need to learn more about how compressors work at a high level. 

How does a compressor work? 

Compressors exist in two major formats: Hardware and software. Today most people use software compressors, but the core mechanices of compressors are the same across both hardware and software. 

Here are the key components of a compressor you should know: 

1. Threshold

The threshold is the starting point of compression. It's measured in decibels (dB). Setting the threshold tells the compressor where to start compressing. The signal is said to be compressed only when it goes above the threshold. The audio below the threshold will not be compressed. 

2. Ratio

Ratio tells your compressor how much to reduce the volume (or gain) when the threshold is reached. Commonly, it is expressed as 2:1. 2 refers to the initial signal, and 1 refers to the amount which the signal will be reduced. That means a 2DB signal would be reduced by 1 DB, an 8 DB signal would be reduced by 4DB, etc.

Once a signal exceeds the threshold, the ratio setting determines how much has to be lowered. The quantity by which it is turned down is known as gain reduction, or GR. A lower ratio like 2:1 is light compression, 3:1 is a medium compression and is very commonly used, and 10:1 and above is extreme compression which is generally considered to be limiting, technically speaking. 

3. Attack and release

Attack and release influence how quickly (or slowly) the compressor activates and how long the effect lasts. A fast attack, usually measured in milliseconds (ms), implies that the compressor will perform full compression immediately after the audio crosses the threshold.

Meanwhile, a slow attack will take some time to apply complete compression to the audio once it crosses the threshold.

Release, on the other hand, is the exact opposite of attack. This is the time it takes for compression to stop after the audio signal falls below the threshold. A compressor set with a fast release lets go rapidly after its initial clampdown, whereas a compressor with a slow release holds on, compressing for a little longer before releasing.

4. Knee

A knee controls how strongly the compressor clamps down on the audio that passes through it. 

A soft knee eases into compression gradually, producing a less loud effect than its hard counterpart. It is basically how the compressor transitions the audio between non-compressed and compressed states.

5. Makeup gain

When a signal is compressed, its overall volume becomes quieter. Makeup gain turns up the volume for that track to compensate for the gain that you lose by compressing the signal.

How to compress audio

For those new to audio engineering, learning how to use a compressor can be daunting. However, there are user-friendly compressors  available in free tools like GarageBand, Audacity, and Resound. These tools are designed to make compression straightforward and accessible. 

Let's take a look at how to use them effectively.  

1. How to manually compress audio in GarageBand

The Garageband compressor is a stock plugin that anyone can learn to use easily.

Garageband provides some presets that can be really helpful in getting started. It's a good idea to use them until you feel more comfortable and better understand what you're doing, and these configurations are a great place to start. 

Here's a simple guide on how to use GarageBand to compress your audio:

2. How to manually compress audio in Audacity

Audacity is a free audio editor available for download on Windows, Mac, and Linux. Audacity can compress MP3, WAV, AU, and OGG audio files. 

Follow the steps below to compress audio in Audacity:

3. How to automatically compress, mix, and master your audio in Resound

Resound uses AI to automate tedious production tasks, including compressing your audio files. If you don’t want to learn how to use a compressor but would rather just upload your files and automatically get a professionally mixed podcast, Resound is for you! 

Here's how it works: 

Common mistakes with compression

Compression can make your audio sound amazing, or it can ruin a perfectly good recording. When you’re getting started with compresion, make sure that you avoid these mistakes… 

1. Don’t over compress 

Applying too much compression can make your audio sound squashed and unnatural. It can remove the dynamics from the audio, making everything sound at the same volume, which can cause unpleasant listening experiences for your listeners. In some cases, overcompression will actually make your audio sound like it’s distorting, even if the original audio was not. 

2. Don’t let audio pump with bad Attack and Release settings

The attack time is how fast the compressor reacts when the sound gets too loud. The release time is how quickly it goes back to normal after the loud part is done. If you don't get these times right, your audio might sound like it's "pumping" or taking awkward breaths, which isn't what we want for a smooth podcast experience.

3. Don’t set the Threshold too low 

If the threshold is too low, even the quieter moments of the audio will trigger the compressor to start working. It's similar to having a microphone that picks up every whisper in a room. If the compressor is taking effect on your quietest moments, then it will absolutely squash the loudest moments, and sometimes can make your overall volume too quiet.  Finding the right balance in Threshold is crucial to maintain the natural flow of the audio.

4. Don’t rely solely on presets

While presets can be a good starting point, every recording is unique. Relying solely on presets without understanding how they affect the audio can lead to terrible results. If you’re using an AI compressor like Resound then you can trust the tool to automatically make the adjustments for you, but if you’re manually compressing then be careful with presets. Use presets as a starting place, but tweak them to make sure they are setup to serve your specific audio recording well. 

5. Don’t forget to optimize your audio for multiple device types 

Forgetting that podcasts are enjoyed on various devices, from fancy headphones to simple smartphone speakers, can lead to a misstep. Ignoring the need to check how compressed audio sounds on these different devices might result in an inconsistent listening experience.

6. Don’t let compression bring out the room noise and background sounds

Compression can raise the volume of quiet parts of a recording, which might amplify unwanted background noises. It's essential to record in a quiet environment or use noise reduction tools before compressing. If you use Resound Enhance to compress your audio we’ll also remove your background noise, so you don’t have to worry about this yourself. 

Final thoughts

Compressing your audio is critical, but not everyone has time to learn the ins and outs. With Enhance by Resound, you get more than just compression. It enhances your entire audio experience by removing background noise, leveling your tracks, compressing and equalizing, and even mastering them to streaming standards. It will even avoid the 6 common compression mistakes we listed for you automatically, no experience required.  

Start automating your mixing and mastering today!

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Resound.fm Team

Resound's team is building the future of podcast editing: An AI podcast editing app for creators. Here at Resound we're writing about the creative process to help content creators thrive. Picture is Ernst Chladni, the inspiration for our brand. Hear his story at resound.fm/about

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