Basically, what do you use to record an audio? – Phones, cameras, laptops, video-making devices and probably top-of-the-range microwave ovens, too. But unless you’ve got the latest dictaphone or microphone, the emphasis on a product’s design is usually thrust upon its other features, such as video quality and speed.
But there’s often a digital solution for poor-quality off-the-cut recordings, and the good news is that you will usually have more time to put into correcting audio files that you had to prepare for the recording itself. In this guide, we’ll show you how to use basic audio-processing techniques to greatly improve any audio, as title suggests “how to clean up recorded audio”.
What will you need?
- Reaper – This guide describes how to process audio with Reaper, but the underlying techniques will work in other software. Download the Reaper evaluation at Reaper’s website.
Step 1: Install and Configure Reaper
- Once you’ve downloaded and installed Reaper, oven it and drag some audio from Explorer on to the timeline. A new channel will appear along the bottom row, next to the Master (output) channel. You can use the magnifier by the horizontal scroll bar to zoom into the audio file as far as necessary.
- Use the magnet icon, or Alt+S, to disable “snap to grid”. This will allow you to select a custom area by clicking the timeline above the audio region. Ctrl+Del will chop out an area (Image A). You can look your selected timeline region with the green button to the right of the play button. Click an audio channel;s FX button for a list of plug-ins to lay over the track.
- After any changes, the original audio file remains the same. To commit the changes made in Reaper, go to File -> Render or press Ctrl+Alt+R to bring up the Rendering options (Image B). You can Render the entire file or selected portions on the timeline. The default settings will be appropriate, so click on the “Render 1 File” button to commit your changes to new audio file.
Step 2: Solve common Noise problems
It’s not unusual to be left with annoying wind noise after recording something in the open air. However, chances are it can be blocked out. Import the audio into Reaper, click the track’s FX channel, and then select ReaEQ. When you can hear only the wind, its energy is toward the left of the graph.
- We can remove the left-side low-pitched audio using a Low Shelf or High Pass filter (band one in Reaper). Select “High Pass”, and drag node 1 down, and left and right (Image C). Moving node 1 to the right takes out more wind noise, but starts to remove some of the voice signal, especially the male voices. It’s upto you to find the right balance.
Audio is only as good as the room it is recorded in. If your room is too resonant, it can sound as if a wine glass is left ringing after every word has been spoken. To sort this out, you need to throw your audio into Reaper, click FX, and select ReaEQ. Drag node 3 as high as it can go, and reduce the Bandwidth to 0.10.
Drag the node or tweak its Frequency slider while playing the ringy audio. This will emphasize certain frequencies. Search for the ringing sound; when you find it, crank the Gain down to below 0. Adjust the Gain and Bandwidth to reduce the ring and leave the desired audio intact (Image D). You may need to use multiband nodes and additional ReaEQs.
Problem: Power-Line Hum
Badly grounded equipment can introduce a 60Hz power-line hum in your signal. You can curtail it. Drag the audio into Reaper, click FX, and select ReaEQ. This will bring up a customizable EQ and an analysis of the audio while it’s playing. Try to isolate a part of the signal with the hum to make this easier.
Pull down the numbered circles at the points where the hum is active. The blue dips should be placed to counteract the yellow bumps. You can change the “thickness” of the cuts with the bandwidth control – this can prevent the desired audio from being degraded. It’s unlikely you’ll entirely remove the hum, but you can reduce it.
Step 3: Advance Processing
Sometimes a poorly edited audio file will have cuts that have been made at inappropriate times, resulting in clicks during audio playback. If your audio files has this problem, zoom in as close as possible to the clicking point, and there should be a moment when the audio wave moves almost vertically.
Whenever Reaper makes a region, it creates a microscopic fade in/out, reducing the volume at the edges. If we select the area around the vertical in Reaper and hit Ctrl+Del, it’ll be chopped out and will fade nicely between the waves on either side (Image E). You’ll need to zoom in and find every click.
Problem: Background noise
To reduce constant noise, import the audio into Reaper and click FX in the channel below (Image F). Choose “VST:ReaFir”. Change the Mode to Subtract, and trick the “Automatically build noise profile” box. Play a part of your clip with only the noise audible – not any wanted parts – to build a profile. Untick the box, hit Play, and noise should be reduced.
Another way to reduce background noise is with a gate. Add ReaGate instead of – or as well as – ReaFir. Increase the level of the ReaGate to a maximum and play the audio. Nothing should be audible. Move the ReaGate down again while playing the audio until you reach a setting where the wanted material is audible, but the noise isn’t.
There are plenty of ways to reduce, or even remove, common audio problems. But in doing so, consider the effect that the cleanup is having on the desired audio – sometimes it can be better to keep some of the unwanted sound if removing it completely would degrade the material. Human speech, for example, can easily lose its natural feeling and expression when it is messed around with too much.
Keep in mind that the certain things just aren’t possible to get rid of completely when editing audio. Background sound can be lessened, but the results depend on the type of noise. Constant noise that stays similar in level and content is easier to take away, but sounds with a more random character – crowd noise, for instance – can’t always be removed.