Podcasting Tips: Making Your Podcast Sound Better with Normalization and Limiting
Do you want your podcast to sound better? Why let sound quality get in the way of your excellent content?
In my last post, I told you about using audio compression to keep your levels more consistent across your podcast. This time, we will cover two more important effects that can improve the overall sound of your episodes: normalization and limiting.
Still to come in the series I will take a look at equalization (EQ), noise reduction and putting it all together.
Let me start by saying that normalization is pretty straightforward – except that it is not. In the world of audio, the term normalization may mean two things: peak normalization or loudness normalization. Loudness normalization is an important topic, but we are going to need to save that for another post. Peak normalization is what we are going to focus on here.
What is Peak Normalization?
In my last post, I wrote about compression. Compression is reducing the dynamic range between your loudest sounds and quietest sounds. Peak normalization, on the other hand, adjusts the gain across the entire recording. It is pretty straightforward. Peak normalization looks for the highest signal level (the peak) in the recording and adjusts the overall gain so that that the highest level is set to a level you determine.
Here is a file recorded in Garage Band with no processing at all.
Here is the same file with compression added.
Now, here is the same file normalized.
Note: Garage band makes this process pretty simple, but it is a little tricky to figure out. In Garage Band, adding compression doesn't impact the shape of the waveform until you export the file. Normalization can only be applied during export.
Most of the time, normalization is used to increase the gain to its highest possible level without going over 0dB which can cause clipping. Many audio pros suggest setting this at .1 dB. I set mine at .25 dB. That means the very highest peak in my recording will not cross .25 dB.
Peak normalization is so simple, you can do it manually. Just increase the gain across the entire track until the peaks are where you want them. However, using built-in normalization in your audio workstation is a much safer bet. If you do it manually, you need to be really sure you haven't accidentally set your gain, so any peaks are over 0dB.
What happens if you go over 0dB? Sometimes you get lucky, and nothing happens. Technically, anything over 0dB is considered clipping. Usually, a little clipping here and there doesn't cause a huge problem. However, too much clipping can create distortion. Your best bet, unless you are an audio pro simply don't let anything go over 0dB. Using peak normalization is an easy way to ensure never crossing that threshold.
I held a long debate with myself about including limiting here. Limiting can be a very helpful tool, but it can also be disastrous if used wrong. Limiting is not a substitute for compression or normalization.
Limiting is a type of compressor. It is just a very unforgiving compressor. Whereas a compressor smoothly reduces the gain of the signal over a specific threshold dB using a predetermined ratio of reduction, a limiter basically crushes anything above that level.
Using a limiter the wrong way can lead to some very strange results. Instead of a gentle reduction of the peaks, the limiter will not allow any signal to cross the threshold. When used incorrectly, the result can be the same as the distortion caused by clipping. However, limiting has some practical applications.
Here is where it may be useful. There may be times when, even after compressing a track, there are a few stray peaks that are way above the average for the recording. If you normalize the file using peak normalization, you may find the overall level of the recording seems very low. The reason is that it is using those stray peaks as the maximum level. Since normalization is setting the level of the entire track based on the highest peaks, those strays are hitting the threshold and not allowing the rest of the gain to be increased.
Here is a recording in Adobe Audition that has some stray peaks.
Here is what happens when it is normalized.
If you look closely, you will see that nothing happened. Those strays were counted as the peaks and couldn’t be raised any further without exceeding the threshold. Using a limiter can lower the level of those stray peaks so that the overall gain can be raised to the pre-selected level.
Here is a hard limiter applied at -3 dB which appears to be the maximum gain if you eliminate the stray peaks.
Now, let’s see what that looks like with normalization.
Let’s see those side by side. On the left, the file normalized before adding a limiter. On the right, the file normalized after adding the limiter.
Use Your Ears!
The most essential tool in your toolkit when working with compression, normalization, and limiting is your ears. Whenever applying effects of any sort, be sure to listen back carefully. If something sounds wrong, something is wrong. Go back and remove the effects one by one until the problem goes away and then try again with different settings until everything sounds right. It takes some trial and error, but once you get the hang of it, it won't take long to get your audio sounding great.