I have had a problem balancing audio clips on my PC-edited home videos. For example, I created a 10-minute video celebrating my daughter’s life as a gift for her birthday. The project included old video clips as well as still photos of her at various ages. I added music from various sources (including tapes and CDs). The amplitude from one sound clip to another was not always the same. While the software I have allows for decreasing amplitude and equalization, I could not tell the actual level of each group of sound clips to make them uniform in volume throughout the whole project. I believe the input recording of these clips is an important factor, but I am curious to know if there is anything else that can be done (something real easy, like File/Select All/Audio Clips/Make Amplitude Uniform). Any suggestions?
Thanks for the question. Audio is not only a difficult subject it is also subjective. You are right, input levels are very important so that you can have a strong clean signal to use for audio mixing your project. Of course, use the highest quality audio that you can. For example, the most pristine analog cassette will always introduce more noise to your audio than a well produced audio CD just because of the inherent inferiority of the recording medium. In short, even if the cassette and the CD were input at approximately the same level in most cases the clarity and dynamic range of the CD will win out over the cassette. Mixing audio from different sources with different types of content, i.e. natural sound from a home video, narration recorded from a mike or high fidelity music from a CD is a tough task. How can you succeed? Here are a few guidelines that will help when mixing a project.
Editing software like Premiere, and others, has a function called "Normalize," but this just raises the level of an audio clip relative to itself not to other clips. There is no setting that adjusts clip levels relative to one another. Even if you could have your computer make all your levels uniform, it would not sound (to the human ear) like all the sounds were same volume. Why? Because electronics do not differentiate between frequencies (high pitch and low pitch sounds). Therefore, the only way to balance your levels so that they sound even is to listen. Use your ears and trust what you hear.
A trick used by audio professionals is to listen to a soundtrack at a very, very low volume. This can make it easier to find where program material is too low or too high so you can adjust the levels accordingly. Try it. You’ll see what we mean.
In addition, it is a good idea to listen to the project on the same type of monitor that your audience will use. After mixing on your PC, make a videotape of the project and listen to it on the speaker of a TV. If something jumps out or gets lost in the mix, you’ll need to remix and try again. True, this sort of adjusting can be a time-consuming process, but when you are finished, you’ll have a spectacular soundtrack to show for it.
When all else fails, you can squash it. We leave this for last because it is the last line of defense. The compressor/limiter is a useful tool that you can use when editing audio. A simplified explanation of the compressor/limiter is that it lowers the peak sounds so that they are closer to the lowest sounds. Some software including Premiere, Vegas Video and Media Studio Pro offer a compressor/limiter in their list of audio effects. Watch out though, use of compression will degrade the fidelity of your overall program. You should only use this after trying every other option.
With the use of diligent mixing techniques and critical listening, together with signal compression from a compressor/limiter you can dramatically improve the audio content of your video productions.