Tutorial: Matching Ambient Sound Between Clips in iZotope RX4 Advanced

"Normally, the way to fix that would be to try to find some of that same ambience from somewhere else," Prisk says, "or wild sound that you've recorded on location, and try to plug it in underneath. The problem with that is that it ends up essentially doubling the amount of ambience that you have, and it gets louder or a bit too much."

Let's take a look at how RX4 handles this issue. Figure 2 (below) shows that same clip in RX4. The ambience changes dramatically at about the 2.5-second mark.

Figure 2. The press conference clip with the uneven ambience in iZotope RX4. Click the image to see it at full size.

The first step is to find a spot without any dialogue (in this case, from about 0.9 seconds to 1.2 seconds into the clip), select it, and choose Ambient Match from the panel on the right (Figure 3, below). The Ambience Match module opens (Figure 4, below Figure 3).

Figure 3. Choosing Ambience Match

Figure 4. The Ambience Match module

In the Ambience Match module, click Learn, as shown in Figure 4 (above). This will instruct iZotope RX4 to learn the ambience for the selected portion of the clip. Once RX4 has learned the ambience, you can make a new selection and add it to the newly selected portion of the clip by clicking Process (Figure 5, below). Note that you don't have to be especially careful of where your selection starts and ends. "The nice thing about Ambience Match," Prisk says, "is that it doesn't duplicate sounds. It's not going to get any louder, even in those sections where your selection" might be overlapping areas that already have ambient sound that's comparable to the ambience you told RX4 to "learn."

Figure 5. Click Process to apply the learned ambience to the selection. Click the image to see it at full size.

After you click process, a progress window opens (Figure 6, below) as RX4 processes the ambience matching.

Figure 6. The Ambience Match progress window

In the clip below, you can hear how Ambience Match changed the ambience on the press conference scene.

So, as you can hear, Ambience Match has created a near-perfect match between the ambient sound just before where our selection began (Uncle Bennie's first few phrases) and the first part of our selection where we added the learned ambience. And the sound level of the ambience remains consistent throughout, with no duplication or doubled sound. The match isn't quite as close at the end of the selection, but we can go back and tweak that as needed. "But even as is," Prisk says, "that's completely usable."