Sound mixing is a crucial step in post-production, blending audio elements into a cohesive soundtrack. It enhances emotional impact, guides audience attention, and creates realism. In narrative documentaries, sound mixing supports the story, builds atmosphere, and ensures dialogue clarity.
Techniques include equalizing for clarity, compression for consistency, and reverb for space. Music mixing involves setting levels, equalizing tracks, and sidechaining for dialogue. Sound effects are layered, panned, and given realistic spaces to create immersive soundscapes.
Importance of sound mixing
Sound mixing is a crucial step in post-production that involves balancing and blending all the audio elements (dialogue, music, sound effects) into a cohesive and immersive soundtrack
A well-mixed soundtrack enhances the emotional impact of the story, guides the audience's attention, and creates a sense of realism and space
In narrative documentary production, sound mixing plays a vital role in supporting the story, building atmosphere, and ensuring clarity and intelligibility of the dialogue
Dialogue mixing techniques
Equalizing for clarity
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Using equalization (EQ) to sculpt the frequency spectrum of dialogue recordings, emphasizing the important speech frequencies (typically 2-4 kHz) for improved clarity
Removing unwanted low-frequency rumble, room resonances, or high-frequency hiss to clean up the dialogue
Applying high-pass filters to reduce background noise and low-pass filters to soften sibilance or harsh consonants
Example: Boosting the 2-4 kHz range to bring out the clarity in a softly spoken interview
Compression for consistency
Utilizing dynamic range compression to even out the variations in dialogue levels, making quieter parts more audible and louder parts less overpowering
Setting appropriate threshold, ratio, attack, and release times to achieve a natural-sounding compression without pumping artifacts
Applying gentle compression to the dialogue bus to glue the various dialogue tracks together and maintain consistency throughout the mix
Example: Using a compressor with a 2:1 ratio and a medium attack/release to even out the dynamics of a conversation recorded in a noisy environment
Reverb for space
Adding reverb to dialogue to create a sense of space and match the visual environment
Choosing appropriate reverb types (room, hall, plate) and adjusting parameters (decay time, pre-delay, early reflections) to simulate realistic spaces
Using send/return routing to apply reverb selectively to dialogue tracks, allowing control over the wet/dry balance
Example: Applying a short room reverb to dialogue recorded in a small office to match the visual space
Music mixing approaches
Setting appropriate levels
Balancing the overall level of the music track relative to the dialogue and sound effects, ensuring that it supports the story without overpowering other elements
Riding the music levels dynamically to accommodate changes in the scene's emotional intensity or dialogue delivery
Using automation to create smooth level transitions and avoid abrupt changes
Example: Lowering the music level during important dialogue exchanges and gradually raising it during montage sequences
Equalizing music tracks
Applying EQ to music tracks to carve out frequency space for dialogue and sound effects, preventing frequency masking and clutter
Cutting or reducing conflicting frequencies (e.g., low-mids) in the music that may interfere with the clarity of dialogue
Boosting or attenuating specific frequency ranges to shape the tonal balance of the music and suit the overall mix aesthetic
Example: Applying a low-mid cut around 200-400 Hz to a music track to create space for the dialogue's fundamental frequencies
Sidechaining for dialogue
Using sidechain compression to duck the music level automatically when dialogue is present, ensuring dialogue intelligibility
Setting up a compressor on the music track with the dialogue track as the sidechain input, triggering the compression when dialogue exceeds a certain threshold
Adjusting the sidechain compressor's settings (threshold, ratio, attack, release) to achieve a natural-sounding ducking effect without pumping artifacts
Example: Sidechaining a music bed to the narrator's voice-over, creating automatic level dips in the music whenever the narrator speaks
Sound effects mixing
Layering multiple effects
Combining various sound effect recordings to create rich and detailed soundscapes that enhance the realism and immersion of the scene
Selecting complementary sound effects that work together harmoniously without cluttering the mix or masking important elements
Adjusting the relative levels, EQ, and panning of each sound effect layer to create a balanced and cohesive overall sound
Example: Layering multiple city ambience recordings (traffic, pedestrians, distant sirens) to create a convincing urban soundscape
Panning for directionality
Using stereo panning to position sound effects in the stereo field, creating a sense of directionality and space
Matching the panning of sound effects to the visual placement of objects or actions on-screen, reinforcing the connection between audio and visuals
Employing subtle panning automation to simulate movement or changes in perspective
Example: Panning a car passby effect from left to right to match the vehicle's movement across the screen
Creating realistic spaces
Utilizing reverb, delays, and other spatial effects to place sound effects in realistic acoustic environments that match the visual setting
Choosing appropriate reverb types and settings to simulate the size, materials, and characteristics of the depicted space
Applying distance-based attenuation and filtering to sound effects to create a sense of depth and perspective
Example: Adding a long, dense reverb to a gunshot sound effect to simulate the acoustic space of a large cave or canyon
Mixing for emotions
Supporting the story
Crafting the sound mix to support and enhance the emotional arc of the story, reinforcing the intended mood and tone of each scene
Using music, sound effects, and dialogue processing to create a cohesive emotional experience that aligns with the narrative's goals
Making mixing decisions based on the story's needs, prioritizing elements that serve the narrative and emotional impact
Example: Emphasizing unsettling sound design elements during a tense, suspenseful scene to heighten the sense of danger or mystery
Building tension vs relief
Manipulating the sound mix to create a sense of tension, suspense, or unease during dramatic or conflicting moments in the story
Using techniques such as increasing the presence of low-frequency drones, applying dissonant or atonal sound design, or creating a sense of claustrophobia through close-miked recordings
Contrasting tense moments with periods of relief or resolution, using more open, spacious, and harmonious sound design to signify a release of tension
Example: Gradually building tension in a chase scene by incrementally increasing the intensity and complexity of the sound effects, then abruptly cutting to silence or a calmer soundscape after the resolution
Guiding audience focus
Utilizing the sound mix to direct the audience's attention toward key story elements, characters, or emotions
Emphasizing or isolating specific sounds or dialogue lines that carry narrative significance, making them stand out in the mix
Reducing the prominence of non-essential background sounds or music during crucial moments to minimize distractions and maintain focus on the important audio information
Example: Bringing the sound of a ticking clock to the forefront of the mix during a scene where time is of the essence, underlining the urgency of the situation
Mixing workflow tips
Organizing the session
Establishing a clear and logical structure for the mixing session, using track folders, color-coding, and naming conventions to keep the project organized
Grouping related tracks (e.g., dialogue, music, sound effects) into buses or submixes for easier management and processing
Using markers, regions, or labels to identify key sections, cues, or transitions in the timeline
Example: Creating separate track folders for interviews, voiceovers, location sound, and archival audio within the dialogue group
Mixing in passes
Approaching the mixing process in focused passes, dedicating each pass to a specific aspect of the mix (e.g., dialogue, music, sound effects)
Starting with a rough balance pass to establish the overall levels and relationships between elements, then refining each component in subsequent passes
Utilizing automation and real-time mixing techniques to fine-tune the mix and create dynamic changes over time
Example: Beginning with a dialogue pass to ensure clarity and intelligibility, followed by a music pass to set the emotional tone, and finally a sound effects pass to enhance the realism and immersion
Printing stems for flexibility
Rendering separate stems (submixes) of the key audio components (dialogue, music, sound effects) in addition to the final full mix
Providing stems to the client or post-production team for flexibility in future revisions, localization, or remixing for different deliverables
Ensuring that the stems are properly labeled, time-aligned, and free of processing that may limit their usability in other contexts
Example: Delivering a set of stems that includes a cleaned-up dialogue stem, a music stem with separate tracks for score and source music, and a sound effects stem with backgrounds and hard effects
Loudness standards
Broadcast requirements
Adhering to the specific loudness requirements set by broadcast networks or regulatory bodies to ensure consistent and compliant audio levels
Measuring the integrated loudness (LKFS/LUFS) of the mix over the entire program duration and adjusting the overall level to meet the target value
Applying true peak limiting to prevent digital clipping and ensure compatibility with downstream processes
Example: Mixing a documentary for television broadcast to an integrated loudness target of -24 LKFS and a true peak limit of -2 dBTP, as per the EBU R128 standard
Online platform specs
Following the loudness specifications and best practices recommended by online streaming platforms (e.g., Netflix, YouTube, Vimeo) for optimal playback on various devices
Considering the platform's encoding and normalization processes when setting the mix levels and dynamics
Providing separate mixes or deliverables tailored to the specific requirements of each platform, if necessary
Example: Delivering a mix optimized for YouTube, targeting an integrated loudness of -14 LUFS and a true peak limit of -1 dBTP, as per YouTube's audio guidelines
Metering for compliance
Using dedicated loudness metering tools and plugins to measure and monitor the integrated loudness, short-term loudness, momentary loudness, and true peak levels of the mix
Calibrating the monitoring setup and metering tools to ensure accurate and reliable readings
Regularly checking the loudness metrics throughout the mixing process to maintain compliance with the target specifications
Example: Utilizing a loudness meter plugin (such as the Waves WLM Plus) on the main output bus to continuously monitor the integrated loudness and true peak levels of the mix
Common mixing challenges
Inconsistent production sound
Dealing with dialogue recordings that vary in quality, level, or tonal balance due to inconsistent production sound or recording techniques
Applying corrective EQ, compression, and noise reduction to minimize the differences between dialogue tracks and create a more cohesive sound
Utilizing dialogue replacement (ADR) or voiceover to replace problematic or unusable production dialogue
Example: Equalizing a dialogue track recorded with a different microphone to match the tonal characteristics of the other dialogue tracks in the scene
Clashing frequencies
Identifying and resolving frequency conflicts between different audio elements that can lead to a cluttered or muddy mix
Using EQ to carve out dedicated frequency ranges for each element, ensuring that they occupy distinct parts of the frequency spectrum
Employing sidechain processing or dynamic EQ to create space for competing elements in the same frequency range
Example: Applying a dynamic EQ to the music track to automatically attenuate the low-mid frequencies whenever the dialogue is present, preventing frequency masking
Retaining dialogue intelligibility
Ensuring that the dialogue remains clear, intelligible, and at the forefront of the mix, even in the presence of complex music or sound effects
Carefully balancing the levels of competing elements and using automation to prioritize dialogue during crucial moments
Applying dialogue-specific processing (e.g., EQ, compression, de-essing) to enhance speech clarity and reduce distracting artifacts
Example: Using a multiband compressor on the dialogue bus to control sibilance and harshness in the upper frequencies while maintaining the body and presence of the speech
Mixing tools and plugins
Essential equalizers
Parametric EQs: Versatile equalizers that allow precise control over the frequency, gain, and bandwidth of each filter band, enabling surgical adjustments to the tonal balance
Graphic EQs: Equalizers with fixed frequency bands and slider-based controls, useful for quick and broad tonal shaping
High-pass and low-pass filters: Essential tools for removing unwanted low-end rumble or high-frequency noise and defining the frequency boundaries of each element
Example: Using a parametric EQ to notch out a specific resonant frequency in a dialogue recording that is causing harshness or feedback
Compressors and limiters
Dynamics processors that control the dynamic range of the audio signal, reducing the difference between the loudest and quietest parts
Compressors: Used to even out variations in level, add punch and sustain, or glue elements together
Limiters: Used to prevent the signal from exceeding a set threshold, protecting against digital clipping and ensuring compliance with loudness standards
Example: Applying a gentle bus compressor to the dialogue submix to even out the levels and create a more consistent and cohesive dialogue track
Reverbs and delays
Spatial effects that simulate acoustic environments and create a sense of depth, space, and placement in the mix
Reverbs: Used to place elements in realistic or stylized spaces, ranging from small rooms to large halls or abstract environments
Delays: Used to create echoes, slap-back effects, or rhythmic patterns that enhance the texture and dimensionality of the mix
Example: Using a short, bright room reverb on the dialogue to subtly enhance the sense of space and match the visual environment of an interior scene