The audio side of video is often not well recorded due to small production budgets and short time frames. Therefore, during post-production, producers can be assaulted by a series of previous sonic missteps. An annoying rumble or hum in the low end is a common problem in audio recorded for video.
Certainly many of the software plugins on the market that filter out noise work very well. Though, under a tight deadline, it may prove impossible to seek out, purchase, and learn the functions of whatever new plugins you may find. As an easy alternative, use the standard eq and reverb plugins provided in your video or audio software.
Use these procedures in tandem with your default plugins to help rid your audio recording of unnecessary and distracting noise:
First, use a Single Band EQ to try and cut out the offensive hum. This type of EQ will cut out all sound below or above a certain frequency. For example, since low rumbles generally occur around 60 Hz, you can use a Single Band EQ to cut out everything below 80 Hz which will remove the hum without adversely affecting the dialog.
Second, use a Parametric EQ to “notch” targeted areas by using a very small width of the sound spectrum to decrease a specific tone and its octaves, such as 60 Hz, 120 Hz, and 240 Hz. By targeting only small areas of sound one hopes to rid the offensive noise while preserving the surrounding frequencies.
Next, a Parametric EQ can also be used to boost the wanted audio. Boosting the desired frequencies will give them prominence over the unwanted noise and thus redirect the listener’s attention from the noise. For instance, put a small hump in around 5 Khz will amp the human voice over a lower rumble.
Fourth, after cutting out the lower end, a bit of reverb can be used on the mix. Such an effect can wash over and warm up a “tin can” feel that might come from taking out the bottom end.
While the above tips are very basic and will not by any means eliminate the problems of poorly recorded audio, they will definitely improve the sound of a poor recording when the dialog and hum are vying for the listener’s ear.
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