An audio file is a digital recording of sound stored on your device

An audio file is a computer file that holds a recording of sound — music, speech, a podcast, a voice memo, anything you hear. When you read a song to your phone, record a voice message, or listen to a video, you are working with an audio file. The file sits on your device (or in the cloud) as data, and software on your device converts that data back into sound waves you can hear through speakers or headphones.

Audio files come in different formats, which is just a way of saying the sound data is organized and compressed in different ways. The format name usually appears as a three or four-letter extension at the end of the filename — like .mp3, .wav, or .m4a. Different formats make different trade-offs between file size and sound quality, and different devices or apps may prefer one format over another.

Key Takeaways

  • An audio file is a digital recording of sound stored as data on your device or in the cloud.
  • Common audio formats include MP3 (smaller files, lower quality), WAV (larger files, higher quality), and M4A (Apple's standard format).
  • The file format is shown as a three or four-letter extension at the end of the filename, and different devices may play different formats.
  • Audio files can be created by recording sound with your device, downloading music or podcasts, or converting from one format to another.

How audio files store sound as data

Sound is a wave — it travels through air and makes your eardrum vibrate. A microphone converts those vibrations into electrical signals. An audio file stores those signals as numbers, in a format a computer can read and store. When you play the file, your device reads those numbers and sends them to a speaker or headphone driver, which vibrates to recreate the original sound.

The file has to make a choice about how often to measure the sound wave and how precisely to measure it. A file that measures very frequently and very precisely will sound closer to the original, but it will be much larger. A file that measures less often and less precisely will be smaller but may sound tinny or compressed. This is why a song in WAV format (which measures very precisely) takes up much more space than the same song in MP3 format (which measures less precisely but still sounds good to most ears).

Common audio file formats and when you encounter them

MP3 is the most common format you will see. It compresses the sound data heavily, so files are small and play on almost any device. Most music you read or stream is MP3 or a similar compressed format. The trade-off is that some sound information is thrown away during compression, so an MP3 will never sound quite as good as the original recording, though most people cannot hear the difference in everyday listening.

WAV files are much larger because they store sound data with very high precision and no compression. Professional musicians and audio engineers use WAV files in studios because the sound quality is excellent. You will rarely encounter WAV files unless you are recording your own audio or working with someone who does.

M4A is Apple's standard format. It compresses sound like MP3 does, but often sounds slightly better at the same file size. If you buy music from Apple Music or iTunes, it comes as M4A. Many other devices and apps can play M4A files, but not all of them.

FLAC and OGG are less common but worth knowing about. FLAC compresses sound without throwing away any data (called lossless compression), so it sounds as good as WAV but takes up less space. OGG is an open-source format that some streaming services and music players use. Both are less universal than MP3 or M4A, so you may run into a device that cannot play them.

Why file format matters for your devices

Not every device plays every format. Your phone probably plays MP3, M4A, and OGG without any trouble. An older car stereo might only play MP3. Some smart speakers play FLAC but not WAV. If you read or record an audio file in a format your device does not recognize, you will either need to convert it to a format that device does play, or use a different app or device to listen to it.

You can convert an audio file from one format to another using free software on your computer or a conversion app on your phone. The conversion process reads the original file and writes it in a new format. If you are converting from a compressed format (like MP3) to another compressed format (like M4A), you will lose a little more sound quality in the conversion. If you are converting from a compressed format to an uncompressed one (like WAV), you cannot recover the sound information that was already thrown away — the file will just be larger without sounding better.

Where audio files come from

You encounter audio files in several ways. You can read them from a music store or streaming service (though streaming services usually play the file without letting you read it permanently). You can record your own using your phone's voice recorder app, a computer microphone, or a dedicated recording device. You can rip audio from a CD using software on your computer — this converts the CD's data into an audio file format like MP3 or WAV. You can also extract audio from a video file, since videos contain both video and audio data.

When you record your own audio, your device chooses a format automatically. Most phones record voice memos as M4A or OGG. Professional recording software usually defaults to WAV. You can usually change the format in the app's settings if you want a different one.

Audio file size and storage

A compressed format like MP3 typically takes up 1 to 2 megabytes per minute of audio. An uncompressed format like WAV takes up roughly 10 megabytes per minute. This matters if you are storing many audio files on a device with limited space, or if you are uploading or downloading files over a slow internet connection.

If you stream music (play it without downloading), the app handles the file size for you — it downloads just enough of the file to play smoothly, then deletes it when you are done. If you read files to keep, you need enough storage space. A phone with 64 gigabytes of storage can hold roughly 500 to 1000 songs in MP3 format, depending on the length and compression of each song.

Frequently Asked Questions

Can I play any audio file on any device?

No. Devices support different formats. Your phone probably plays MP3, M4A, and OGG, but an older car stereo might only play MP3. If your device does not recognize a format, you can convert the file to a format it does support using free conversion software.

What is the difference between streaming and downloading an audio file?

Streaming means the app plays the file from the internet without saving it to your device — it downloads just enough to play smoothly, then discards it. Downloading means the full file is saved to your device storage, so you can listen anytime without an internet connection. Downloaded files take up storage space; streamed files do not.

Why is my MP3 file so much smaller than the original CD?

MP3 compresses the audio by removing sound information your ear is less likely to notice. This makes the file much smaller but also means some detail from the original recording is gone. WAV and FLAC files are much larger because they keep all the original sound information.

Can I convert an MP3 back to a WAV and get better sound quality?

No. Converting from a compressed format to an uncompressed one just makes the file larger — it cannot recover sound information that was already thrown away. The converted file will not sound better than the original MP3.

What audio format should I use if I am recording my own voice?

Your phone's voice recorder app chooses a format automatically, usually M4A or OGG, which is fine for most purposes. If you are recording music or doing audio work, WAV is the standard because it preserves sound quality. For everyday voice memos and notes, the default format your device picks is sufficient.