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You've captured great audio and brought it into the editing timeline where you've synchronized and cleaned it up even further. Hisses, hums, clicks and pops have been eliminated or reduced and perhaps you've even applied appropriate effects and filters to sweeten the mix. For one final touch before releasing your masterpiece to the masses, we'll show you how to design a professional sound mix in post, using ducking, frequency gaps and normalization to give your audio a particularly professional polish and set it in a class all its own.
Have you ever watched an interview or a documentary and found yourself annoyed that the dialogue was oftentimes overpowered by the underlying music track, that different portions of the audio seem to be set at varying volume levels or that the entire audio track was just too low to hear everything intelligibly? If you've experienced any of these issues then you know that the last thing on your mind as you left the theater was NOT how great the movie was. No, the thing foremost in your thoughts was the difficulty you encountered as you tried to make sense of what was happening onscreen due to the poorly mixed audio. In order to avoid leaving our audiences with a similar sense of dread we must first place ourselves firmly in their shoes and take the appropriate steps to correct these issues preemptively.
The process of lowering the volume of the music track when dialogue begins, then increasing it again when the dialogue has finished, is referred to as ducking. In this way, the dialogue is never overpowered by the music track. While other editors will have similar capabilities, here's how it can be done using Adobe Premiere Pro. With the voice and music tracks on the timeline, open the Audio Mixer. You will usually find it next to the Effect Controls tab. The Audio Mixer will display a set of sliders and other controls for each audio track on your timeline, in addition to a Master Slider. Find the slider that corresponds to the music track you will be ducking, in this case, Audio 2. Beneath the title, Audio 2, you will see a drop-down list with Read selected. Open the list and select Write. Immediately above the slider are three icons: a speaker, a trumpet and a microphone. Click the microphone icon to enable the track for recording. Next click the red Record button at the bottom of the Audio Mixer window then click the Play - Stop button to its left. As the track plays through, watch the waveform on the voice track while listening carefully through a set of quality headphones. Each time the dialogue or voice over is about to begin, drop the slider to reduce the volume of the music to an appropriate level. Once the person speaking has finished talking, raise the slider to increase the volume. As the slider moves, volume keyframes are being recorded to the audio track. Click the Play - Stop button again to stop recording. Return the playhead to the beginning of the timeline and press the space bar. As the timeline plays through, notice that the slider now slides up and down on its own, automatically ducking the audio according to the keyframes you recorded earlier.
A frequency gap can be used to create a separation between the dialogue and the underlying music track. This allows you to increase the volume of the music, without making the dialogue more difficult to hear, by eliminating the competing frequencies. To do this, go to the Effects window and locate the EQ effect for the appropriate audio type, such as stereo, and apply it to your music track. Open the EQ effect in the Effect Controls window, twirl open Custom Setup and size it as needed to see all the controls. While playing through the audio, adjust the volume on the output slider at the right so the vocal track isn't being drowned out entirely by the music track. Click the Mid3 checkbox to activate that frequency band and drop the gain all the way down to -20dB. Adjust the frequency dial until the vocal track becomes a bit clearer, perhaps around 200 - 500Hz. Next, adjust the Q values to increase the range of frequencies affected and play with these settings a bit until you've achieved the desired effect. Toggle the Bypass checkbox on and off to hear the difference.
Occasionally you may be working with a bit of sound that was recorded too low and you wish to boost the gain of one or more clips. One method for doing this is called normalizing audio. Normalization is the automatic application of a constant amount of gain in order to bring the peak signal up to a predetermined, or target, level. If you wish to normalize a single clip that is already on your timeline, simply select it. Alternatively, if you select a master clip in the Project panel, any amount of gain you apply will be reflected in all instances of that clip throughout the project, including portions of the clip. Once selected, click the Clip menu, go to Audio Options and select Audio Gain. Premiere calculates the clip's current peak amplitude and displays it at the bottom of the Audio Gain dialogue box. If, for example, your clip's current amplitude is peaking at -12dB and you want to boost its max to -3dB then select Normalize Max Peak to and enter -3 in the values field. A gain of 9dB will be applied across the clip, bringing the entire signal up by 9dBs with a maximum peak of -3dB. If you wish to normalize multiple clips at the same time, then Shift-Click to select contiguous clips or Ctrl-Click non-contiguous clips in either the Project panel or from within the sequence. With your clips selected click the Clip menu, go to Audio Options and select Audio Gain. Select Normalize Max Peak to and enter the desired value. With multiple clips selected, the clip having the highest peak will be adjusted by the amount of gain necessary to bring it's max up to the target value and the other selected clips will also be adjusted by that same amount of gain, thereby keeping their relative gain differences intact. Here's the before and after.
Use the ducking, normalizing and frequency gap techniques described here in this segment and you will brand your projects with the highest mark of professionalism, making your name, and your work, synonymous with quality in the mind of your audience.