Can I compress a voice recording?

Voice compression refers to reducing the size of audio files containing spoken words, such as voice recordings or podcasts, by encoding them using audio compression algorithms or codecs. This compression allows the audio files to take up less storage space and be transmitted faster over the internet, while aiming to maintain sufficient audio quality.

According to Adobe, audio compression is useful for making recordings sound more polished by evening out volume differences and smoothing out signals. It is particularly beneficial for voice files since human speech has a lot of repetitive waveforms that can be compressed. Compression enables sharing voice files using less bandwidth when the full dynamic range is not necessary.

Reasons to Compress

One of the main reasons to compress audio files is to save storage space. Uncompressed audio files like WAV and AIFF can be very large, especially for longer recordings. For example, a 3-minute song saved as an uncompressed WAV file at 44.1kHz/16-bit can easily be 30-40MB in size. Compressing the file to a format like MP3 or AAC at a bitrate of 192kbps can shrink it down to just a few megabytes.

This space savings becomes even more significant for larger projects like albums and podcasts. Hundreds of megabytes or even gigabytes can be saved by using compression. This reduced file size makes it much easier to store and transfer lots of audio content.

According to this article, compressed formats are essential for “portable devices, streaming, and most digital distribution channels.” The ability to store more tracks on portable music players, take up less bandwidth for streaming, and reduce download sizes are big advantages of compressed audio files.

Methods of Compression

There are two main methods of compressing audio files: lossy and lossless. Both reduce the file size, but do so in different ways.

Lossy compression permanently removes some audio data to shrink the file size. This discards unnecessary or imperceptible details that most listeners won’t notice missing. Popular lossy audio formats include MP3, AAC, Ogg Vorbis, and WMA ^[1].

Lossless compression squeezes audio data without losing any information. When decompressed, the original uncompressed audio is reproduced bit-for-bit. Common lossless formats are FLAC, ALAC, WMA Lossless, and MQA. These retain complete fidelity while taking up less space ^[2].

For most applications, lossy compression provides sufficient quality at manageable file sizes. But for archiving or high-quality audio, lossless is preferred. The choice depends on your priorities for audio quality versus file size.

Common Audio Codecs

There are several common audio codecs used for compressing audio files and streaming audio online. Some of the most popular and widely supported include:

MP3

MP3, short for MPEG-1 Audio Layer III, is one of the most widely used codecs for digital audio. It utilizes a lossy compression algorithm that reduces audio file size with minimal perceptible loss in quality. MP3 compression can reduce the size of audio files to about 1/10th the original size while maintaining good sound quality. MP3 is supported by nearly all media players and devices.[1]

AAC

Advanced Audio Coding (AAC) is a lossy compression format that was designed to be the successor to MP3. AAC generally achieves better sound quality than MP3 at the same bit rate. It is commonly used by Apple’s iTunes and is the default audio format for YouTube videos.[2]

Vorbis

Ogg Vorbis is an open-source audio encoding and streaming technology. It is comparable to MP3 and AAC in terms of sound quality but is not as widely supported. Vorbis performs well for online streaming and is used by some game engines and media players.[3]

WMA

Windows Media Audio (WMA) is a proprietary audio codec developed by Microsoft. It competes with MP3 and achieves better compression, though it is not as widely supported. WMA files can only be played on Microsoft software and devices.

Bitrates and Quality

The bitrate of an audio file refers to the amount of data processed per second and is measured in kilobits per second (kbps). Generally speaking, a higher bitrate corresponds to better audio quality, as more information is encoded in the audio file.

For compressed audio like MP3 files, a bitrate of 128kbps provides decent quality, while 320kbps is considered high quality and similar to CD quality audio. Lossless formats like WAV and FLAC can have bitrates of 1411kbps or higher.

According to Ultimate Guide To Audio Bitrate & Audio Formats, “For most general listening 320kbps is ideal. Of course, CD-quality audio that stretches to 1,411kbps will sound better.”

As explained in Understanding audio bitrate and audio quality, “A higher bitrate generally means better audio quality. Bitrate is going to determine how much data can be stored in the audio file.”

So in summary, when compressing audio it’s best to use the highest bitrate possible that provides satisfactory quality without creating excessively large files. The higher the bitrate, the better the audio quality.

Stereo vs Mono

When compressing audio, an important consideration is whether to use stereo or mono. Mono audio uses a single audio channel, while stereo uses two channels – one for the left and right speakers. According to KVRAudio, mono compression uses less CPU resources and disk space compared to stereo.

Mono takes up half the space of stereo audio. This is because stereo encoding captures two distinct channels, whereas mono only captures one channel. So if storage capacity or bandwidth is a concern, mono compression may be preferred. According to the KVRAudio forums, the main advantage of stereo compression is a wider soundstage if you have two speakers or headphones. However, for many applications like podcasts, mono audio is sufficient.

Sample Rates

The sample rate refers to how many samples of audio are captured per second in a digital recording. The most common sample rate is 44.1 kHz, which means 44,100 samples are taken per second. This sample rate is considered CD quality since it is the standard used for audio CDs.

Higher sample rates like 48 kHz, 96 kHz, and 192 kHz can capture more audio information by taking more samples per second. However, there is debate over whether the difference is noticeable, especially at 96 kHz and up. According to research from iZotope, humans generally can’t hear much improvement above 48 kHz.

Therefore, 44.1 kHz remains an effective sample rate for most common applications. It provides CD quality audio while keeping file sizes manageable. Unless aiming for absolute peak audio fidelity like in classical music recordings, 44.1 kHz is likely sufficient for most listeners.

Compression Software

There are many software options, both free and paid, for compressing audio files on Windows, Mac, Linux, iOS and Android devices. Some of the most popular and highly rated choices include:

• Audacity – A free, open source, cross-platform audio editor and recorder. It has options to export files in compressed formats like MP3, OGG and WMA.

• GarageBand – Apple’s free music creation software for Mac and iOS. You can share songs or podcasts as compressed AAC or MP3 files.

• ocenaudio – A free cross-platform editor with options to compress WAV files as FLAC, MP3 or OGG.

• FLAC – Free Lossless Audio Codec software to compress files while preserving quality.

• Ashampoo Music Studio – Paid software for Windows with advanced audio compression and editing tools.

Most digital audio workstations, like FL Studio, Ableton Live and Logic Pro, also allow you to export compressed audio files. Overall, there are many great software options to choose from based on your platform and needs.

Sharing Compressed Files

One of the main benefits of compressing audio is being able to share files easily online. Compressed audio formats like MP3 and AAC are designed for maximum compatibility so they can be played on any device.

MP3 and AAC files will play on smartphones, tablets, computers, and any device that supports digital audio. This cross-device compatibility makes sharing easy. You can email compressed audio files, upload them to cloud storage services like Google Drive or Dropbox, share via messaging apps, post on social media, and more.

Services like WeTransfer allow sending large audio files up to 2GB to anyone quickly and easily. The recipient just needs to click the download link. For email, most inboxes support up to 25MB attachments.

Sharing uncompressed audio like WAV and AIFF is more difficult because the files are so large. Compressing makes transferring audio hassle-free across all devices. As long as the recipient has an app or software that can play the format, compressed audio files will work seamlessly.

According to Filestage, the small size of compressed formats combined with universal compatibility makes sharing audio a breeze.

Conclusion

In summary, compressing audio can provide several benefits such as reducing file size for easier sharing and streaming, optimizing dynamic range, and controlling loudness. Common compression techniques include dynamic range compression to shape transients and reduce peaks, data compression like MP3 to reduce file size, and sidechain compression for ducking. While compression can improve listenability and convenience, over-compression can negatively impact quality and dynamics. The optimal approach depends on the source audio and intended application. When used appropriately and with quality codecs like AAC or lossless formats, compression can retain excellent audio fidelity while achieving its aims. Compress thoughtfully, listen critically to optimize settings, and choose the right tool for each task. With a nuanced approach, compression can enable better sharing and playback of voice recordings without sacrificing quality.

To summarize, compress voice recordings when file size, loudness, or dynamic range need optimization, using the proper techniques and high-quality codecs to retain best fidelity. Compression is a useful audio tool when applied judiciously.