Compressing Audio Files: ​​Store Smaller Without Sacrificing Quality

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Compressing audio files allows you to reduce the size of a file, making it easier to upload to your cloud provider of choice, or podcast hosting service, or to share via email. Compression also saves precious space on your hard drive; and—for those audiophiles out there—allows you to normalize audio volume.

We’ll explain exactly what compression means and how you can do it with Descript.

Record or import audio, make edits, add fades, music, and sound effects, then publish online, export the audio in the format of your choice or send it directly to your hosting service.
Create your podcast from start to finish with Descript.

What is audio file compression? 

Audio file compression means simply reducing the file size of your audio while keeping the original data intact. The point is that you save storage space—whether that’s on your computer or cloud account—and make it easier transfer your file to others online. 

Here’s the rub: you can only compress an audio file so much. It’s not possible to take an existing compressed audio file and compress it further. 

How does compression work?

File compression is usually split into two main types: lossy and lossless. The main difference between them is the remaining file size. 

  • Lossless. This format keeps all of your original audio intact, but the tradeoff is a larger file size. WAV files use lossless audio compression. 
  • Lossy. Compressing to lossy formats such as MP3s will use a lower audio bitrate—meaning you will lose a good chunk of the audio file data. You’ll get a much smaller file, making it easier to share and to play or stream, but you’ll also lose some of the overall sound quality. In many cases, the changes will be imperceptible to the listener. 

Think about when you read a physical book. A lossless file would convert the book into a physically smaller size, but all of the words would still be there. Instead of a book that’s six inches wide by nine inches tall, you’re now reading a book that’s four inches wide by six inches tall (with very tiny text).

A lossy file, on the other hand, might have some filler words removed—but you’d still get the gist of the story. Or, it would be reduced to a plot summary, resulting in a much smaller book. 

When to use lossy vs. lossless compression

It’s not really about which type of compression is superior—that’s comparing apples to oranges. Which is “better” depends on why you want to compress the audio. 

Generally, you’ll want to use lossless compression when you want a near-carbon copy of the original audio file, and lossy when you’re not worried about perfection. 

When to use lossless compression

  • Audio quality is king. If you’re not worried about storage space or you’re really worried about audio quality, then a lossless format is the way to go. 
  • Future-proof. Lossless formats also act as a type of insurance policy of sorts in case you want to convert to an MP3 file later on. It’s possible to convert to lossy audio from a lossless format, but not the other way around. 

When to use lossy compression

  • Tight storage space. If you’re worried about storage space, then lossy is probably your best bet. Here’s an example.  Podcasting companies usually pay a monthly subscription to store their files based on size. There may even be a size limit each month on how much can be uploaded. Most podcasters prefer to upload MP3 files to save space and prevent them from having to pay more for extra storage. 
  • Standard uses. As long as you’re not setting the bitrate too low when converting to an MP3 file, your file should be completely adequate for most uses. Neither you nor your listeners should be able to tell the difference. That’s why most digital music and podcast audio are in MP3 format.

Keep in mind lossy compression removes a bunch of the audio data—and once it’s gone, it’s gone. Many free online audio compressors only convert to lossy files, so consider a more professional audio converter like Descript if you want the option to create WAV files. 

How to compress audio file size with Descript

You can compress your audio file by using Descript’s export feature, which lets you choose either lossy compression (MP3) or lossless.

Here’s how:

  • Open the file you want to compress and click the "Share" button in the top right of the app. Then click “Export.” 
  • Choose the “Audio” option.
  • Choose from the available audio formats. 
  • For lossy compression like a MP3 file, choose your desired audio bitrate.
  • If you want, you can customize the normalization (where you make the volume consistent across your entire audio) and sample rate (the rate at which the computer processes digital audio samples to mimic analog sound so our humble human ears can hear it).
  • Click the blue “Export” button to compress your file and save it to your computer.

The bottom line

In most cases you won’t be able to hear much of a difference between lossy and lossless formats. Make your decision based on whether you want to save space or future-proof the audio data.

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