How do you mix audio in a video app?

Audio mixing is an essential part of creating high-quality videos. It involves taking all the individual audio tracks that make up a video project – dialogue, music, sound effects, background ambience – and blending them together into a cohesive final soundtrack. While complex audio mixes were once mainly the domain of professional production studios, advances in video editing apps have made basic mixing capabilities more accessible to amateur video creators and enthusiasts.

In a video project, there may be many separate audio elements that need to be combined. For example, recorded dialogue from on-camera interviews and voiceovers, licensed music tracks used for background scoring, various sound effects like door slams or car engines, and room tone or ambient noise recorded on location. The audio mixer takes all these disparate pieces and ensures they work together seamlessly, adjusting relative volume levels, applying effects processing, and automating changes over time.

The goal of mixing is to create an immersive audio experience that supports the visuals. Dialogue should be clear and intelligible above other elements. Music should enhance mood and emotion without overpowering. Sound effects punctuate important moments. An balanced, polished mix improves overall video production values. Modern nonlinear video editing software like Final Cut Pro, Premiere Pro, and DaVinci Resolve all include built-in digital audio workstations (DAWs) to handle mixing audio directly in the timeline.

This overview covers basic concepts and techniques for mixing audio tracks in video using editing apps. We’ll look at how to import audio clips, arrange multi-track timelines, set volume levels, apply EQ/compression/effects, use automation, and export the final mix. Whether you’re mixing dialogue, music, or sound effects, these fundamentals will help elevate your video productions.

Selecting an Audio Mixer

When mixing audio in a video editing app, the first step is selecting an appropriate audio mixer. Many video editing apps like Premiere Pro, Final Cut Pro, and DaVinci Resolve have built-in audio mixers. These built-in mixers allow you to adjust volume levels, pan audio tracks, and apply basic effects like EQ directly within the app interface. The advantage of built-in mixers is that they are convenient and integrated into the video editing workflow.

However, for more advanced audio mixing capabilities, many video editors prefer using a dedicated third-party audio mixing app or hardware mixer. Popular third-party mixers include Avid Pro Tools, Apple Logic Pro, Ableton Live, and Steinberg Cubase. These specialized mixers provide features like advanced EQ, compression, limiting, noise reduction, automation, and more (Source). The downside is that using a separate mixer adds an extra step to the workflow, requiring you to export audio from the video project, mix it externally, and then re-import the final mix.

So in summary, built-in audio mixers offer simplicity and convenience while third-party mixers provide more advanced mixing capabilities. Consider which features are most important for your video project when selecting a mixing workflow.

Importing Audio Tracks

When importing audio tracks into your video editing software, you’ll need to choose a supported audio file format. The most common formats used for video editing include:

WAV (Waveform Audio File Format) – This is an uncompressed format that provides high-quality audio. WAV files take up a lot of storage space but offer greater editing flexibility (https://www.premiumbeat.com/blog/wav-vs-mp3-audio-for-video/).

AIFF (Audio Interchange File Format) – Another uncompressed format similar to WAV files. AIFF is commonly used on Mac OS systems.

MP3 (MPEG-1 Audio Layer III) – The most popular compressed audio format. MP3 compression allows for smaller file sizes while still maintaining good sound quality (https://www.adobe.com/creativecloud/video/discover/best-audio-format.html).

AAC (Advanced Audio Coding) – A compressed format that is considered superior in audio quality to MP3. AAC is commonly used in MP4 video files.

When choosing an audio format, consider the quality you need balanced with the file size. Uncompressed formats like WAV offer the highest quality but take up more storage space. Compressed formats like MP3 allow for smaller files while still providing decent audio for most video editing purposes (https://www.descript.com/blog/article/how-to-choose-the-best-audio-file-format-for-your-project).

Arranging Audio Tracks

The arrangement of audio tracks refers to how the different elements are organized and layered within the mix. This involves determining the order tracks will play in, which tracks are in the foreground versus background, and how tracks interact with each other.

A common technique is to think in terms of foreground, midground, and background layers (Source). The foreground contains the main, focal sounds like lead vocals or lead instruments. The midground contains supporting elements like backing vocals, rhythm guitars, etc. The background contains ambiences, pads, and other subtle textures.

Typically, you’ll want lead sounds up front in the stereo field and reverb/ambience toward the back. Low frequency sounds like kick and bass may be kept center. Spreading elements too widely can cause phase issues, so be judicious with panning. Keep similar sounds in the same frequency range on separate layers so they don’t clash or muddy up the mix.

Not all tracks need distinct layers – some may share space in the same sonic area. The goal is to arrange parts so the mix feels open and no single element dominates. With planning and practice, you can learn how to effectively layer and organize tracks.

Adjusting Volume Levels

Setting the proper volume levels for each audio track is crucial for getting a balanced, professional mix. The main goal is to achieve optimal gain staging without clipping or distorting the audio. Here are some tips for adjusting volume levels in your video editing app:

Start by normalizing all your audio clips to a target level, usually between -18 to -12 dB. This gives you a consistent starting point. In Adobe Premiere Pro, you can use the “Audio Gain” effect to normalize clips. In Final Cut Pro, use the “Normalize Audio Peaks” filter. Normalizing helps prevent you from having to adjust levels track-by-track.

Next, adjust the levels of dialogue audio to around -12 dB. This leaves enough headroom for dynamic range. As per this Reddit thread, dialogue audio usually sounds best between -0 and -6 dB, but leaving it lower prevents peaking.

For background music, set the volume around -18 to -25 dB. Music should sit underneath dialogue in the mix. If the music overpowers speech, viewers may struggle to hear the words clearly.

Use compressors and limiters to control sudden volume spikes. This helps prevent clipping while maintaining consistent levels. Carefully listen on headphones to catch any sections that seem too loud or soft.

Finally, adjust the master output level to around -12 dB to meet YouTube’s normalization standards, as noted in this article. Now your audio levels should be properly gain staged and ready to export!

Applying Effects

Effects processing is an important part of mixing audio for video. Three of the most commonly used effects are equalization (EQ), compression, and reverb.

An EQ allows you to boost or attenuate different frequency ranges in an audio track. For example, you may want to boost the high frequencies on a vocal track to add clarity and cut low frequencies to reduce muddiness. On music tracks, EQ can be used to accentuate certain instruments or shape the overall tone.

Compression helps control the dynamics of audio tracks. Gentle compression on a vocal track can help even out volume differences and make the vocal sit better in the mix. Harder compression on a slap bass part can tighten up the sound. Compression is often applied across the master bus to glue all the tracks together.

Reverb adds spaciousness and depth to audio tracks. On vocal tracks, reverb can put the voice in a realistic space matching the video environment. On music, reverb builds a sense of space and blend. Reverb is generally added via bus sends so you can control the wet/dry balance.

Using effects like EQ, compression, and reverb skillfully is key to sculpting a professional, polished audio mix for video.

Audio Automation

Audio automation allows you to dynamically adjust parameters like volume and effects over time within your video project. This provides more precision and control compared to setting static levels. Most NLEs and DAWs provide automation features. Popular options include:

Volume automation – Increase or decrease volume gradually in a clip. Useful for fading in/out music or smoothing out level changes. Many apps have envelope editors to draw volume curves over time.

Effect parameter automation – Automate values for reverb, EQ, delay and other effects. For example, you could increase reverb decay on a clip’s tail. Dynamic automation makes mixes sound more professional.

Some apps like DaVinci Resolve provide built-in automation on each audio track’s mixer. Others like Premiere Pro require third-party plugins for advanced automation. The more control over automation curves, the more precision you have in crafting professional sound for your video.

Mixing for Dialogue

When mixing dialogue, the goal is to maximize speech intelligibility so the audience can clearly understand what is being said. There are several techniques to improve dialogue audibility:

First, use equalization to carve out space for the dialogue within the frequency spectrum. Boost frequencies around 2-5kHz for vocal presence and clarity. Attenuate competing sounds in this range.

Next, apply moderate compression to tighten up fluctuating vocal levels. This will make quiet parts louder and loud parts quieter. Set a low threshold and medium ratio to start.

Use volume automation to smooth out any remaining irregularities in the dialogue track’s volume. Carefully ride the fader to maintain consistent loudness through the scene.

Finally, insert subtle reverb to increase speech intelligibility by separating the voice from the acoustic environment. Add just enough to make the dialogue sound natural, not drowned in reverb.

With these techniques, you can optimize dialogue to sound clear and audible within your video mix.

Mixing for Music

When mixing background music or scoring, it’s important to ensure the music enhances the video without overpowering it. The music should complement the visuals and fit the overall mood and pacing of the scene without distracting from dialogue or other important audio elements.

Set background music tracks at a lower volume than dialogue, sound effects, or other featured elements. A good starting point is mixing music around -18 dB to -12 dB, but the exact level will depend on the particular mix. Compression and EQ can help the music blend into the background smoothly.

Use panning and stereo positioning to create space for the music within the mix. Hard panning certain tracks left or right can provide width. Adding subtle reverb may also give the music a sense of space without overpowering the mix.

Ducking, or sidechain compression, on the music track when dialogue or sound effects occur can help foreground sounds punch through cleanly when needed. Automation on the music track can also smoothly lower music volume during important moments. Apply these techniques carefully to avoid unnatural or obvious ducking.

Equalize the music to carve out space for other audio elements. For example, reduce muddy low mid frequencies that could make dialogue less intelligible. Cut or boost specific frequencies as needed so nothing unnecessary competes for the same sonic space.

Use compression to control dynamics and gel the music tracks together into a cohesive bed. Fast attack and release times can prevent music from protruding too much. However, avoid over-compressing, which can flatten the life out of music.

Make sure the tone and genre of background scoring matches the video mood and context. While actual song choices are subjective, the music tone should always complement the visuals.

Subtle additions like risers, transitions, and spot scoring over montages can also blend music and video powerfully. Mix and balance these seamlessly into the overall soundbed.

Listen closely on a variety of speakers to ensure the final music mix sounds full and clear yet subordinate to primary audio elements. Make adjustments if the music ever overpowers, disappears, or conflicts with other aspects of the soundtrack.

(Source: https://www.epidemicsound.com/blog/audio-mixing-for-video/)

Exporting the Final Mix

Once you have finished mixing your audio tracks in your video editing app, the next step is to export the final video with the mixed audio. Choosing the right export settings is crucial to maintain high audio quality. Here are some best practices:

Select a high-quality audio codec like AAC or MP3 when exporting. The sample rate should be at least 44.1kHz or 48kHz for optimal audio fidelity, and 16-bit or 24-bit depth. Stereo is preferable over mono.

For the video codec, H.264 is a standard delivery codec that provides great quality at manageable file sizes. Apple ProRes is higher quality but results in larger files. Make sure to choose a bitrate high enough to avoid compression artifacts in the audio. For YouTube, a bitrate of 8-12Mbps is recommended.

When rendering in your NLE, choose the highest quality presets or dial in custom settings. The “YouTube” or “Web” presets may be too low quality for professional work. Watch your video all the way through after exporting to catch any audio issues.

According to Adobe, the best export settings for Premiere Pro are AAC audio codec, 48kHz sample rate, and stereo channel. For video codec, using H.264 or Apple ProRes 422 provides a balance of quality and file size.