Noise is unwanted in recordings; in fact they do exist and should be removed. Noise in recordings can surely ruin the quality of the mix and decrease the professionalism of your work.
This post covers the noise removal procedure using Adobe Audition 1.5 using Edit View (if you are doing multi-track, double-clicking those tracks in detail brings you to the edit view of the waveform per track). If you are using another audio editing software, then the process should be fairly similar. For details about the noise removal process in your own software, refer to the manual and read this post for some tips.
The actual process
Step 1: Identify the portions of the recording where noise is the only signal.Looking below, I have planned to have at least 1 to 3 idle seconds before I start recording , the purpose is to have portions only for the noise. You can see below that the noise is being highlighted in the beginning portions.
Picture of audio wave
You can hear the mp3 equivalent of this “noise + recorded guitar track”:
Step 2: Capture this “noise only” section using a noise profile data in Adobe audition. This can be done by clicking “Capture noise reduction profile”.
Picture of audio wave with noise
Step 3:Go to Noise Reduction feature in Adobe Audition 1.5, you should see a very similar window as shown below. You can use my noise reduction settings, it works fine. Take note that in the graph, the green dotted below the yellow lines are the noise signals. It is very important to have a profile that consist of “noise only” signals, to avoid degradation of the true music signal that is being recorded.
Adobe audition noise reduction screenshot
Step 4: In the Noise reduction menu, click “Select Entire File”, then click OK. This will apply all the settings and processing on the entire wave signals, including the true musical signals that is being recorded. After this noise reduction processing, you can now see that the noise on the beginning portions has been removed.
Audio wave with noise removed
Listen the guitar track without noise, as you can hear, it sounds clean and pure, no hissing and humming.
Golden Rules of Removing Noise in Recordings
1.) If its poorly recorded because of noise. It is much better to re-recorded it without noise. There are lots of reasons why the recording is noisy which can be as follows (for details of the following reasons, read the related tutorials at the end of this article):
a.) Not using balanced connection and cables.
b.) Using consumer equipment and not professional music production gears. This does not mean that you should buy high-end gears to solve this problem. For example, there is a big difference in noise reduction and clarity if you are recording using PCI/onboard soundcards comparing to the audio interface designed for professional music production like these gears.
c.) Mismatch in the impedance somewhere in the signal chain.
d.) The recording environment is already noisy. To resolve this issue, consider sound proofing your existing live room.
e.) Some hardware issues with your computer or recording equipment that causes noise. This can be a grounding problem that can cause some hum in your speakers or can be captured during recording.
2.) Nose reduction feature offered by many recording software (such as included by Adobe Audition) can only be useful to a certain extent. Overdoing noise reduction takes a lot of original content to the audio, thus the recording don’t sound good anymore despite being noise free.
3.) Implement correct gain staging – it can maximize clarity and minimize noise in your recordings.
4.) Noise reduction is a corrective action, identifying the common causes of noise in recordings and the solutions(more on this topic below) is a preventive action and a much better approach in dealing with noise.
5.) Do not ever perform recording without a preamp. It is because the audio signals that are pickup by your microphone or musical instrument is very weak. If you bypass the preamp and directly record it to your computer, the signal to noise ratio is very poor. This implies that you have a very weak good signal captured but with lots of noise. For details, refer to this article.
So how can you be so sure that you are recording with a preamp? The easiest solution is to use a professional audio recording interface. They all have built-in preamps on its inputs. An audio mixing equipment is not really necessary.
Common Causes of Noise in Recordings and the Solutions
1.) You are plugging guitar or microphone directly into the PCI soundcard line/microphone input. Microphone or any musical instrument outputs a very weak voltage, if you plug it directly into a PCI soundcard input; they are still very weak even if you apply a lot of gain on it on the software mixer. Since the signal is noisy, applying more gain won’t resolve the noise because it’s also amplified along with the desired signal.
Solution: The solution is to use a professional recording preamp for microphones and for plugging guitars. PCI soundcard does not have one and the amplifier on it is very crude it’s not designed for serious music productions. You need to purchase an external pro-recording audio interface either in Firewire or USB type. Make sure this audio interface includes a preamp on its input. Read some guide here on buying an audio interface.
2.) You are using unbalance connectors for long cables. They have unbalanced connectors which are susceptible to noise and signal degradation. Example of unbalanced connectors includes the TS plug and the RCA.
Solution: If long cables are used in guitar recording; it is recommended to use a direct box such as Pyle-Pro PDC21
This will convert the unbalanced line (1/4 TS guitar cable) coming from the guitar into a balanced line XLR, which you can connect to your audio interface microphone pre-amp for a very clean and nice sounding signal.
3.) There is a high background noise (air conditioning systems, outside traffic, etc).
Solution: Make sure the tracking room (where the recordings are done) are free of noise and well insulated. Turn off any noise source before starting the recording, e.g. air condition, fan, etc.
4.) You are bypassing a preamp circuitry in the recording. Preamp conditions and boosts the signal to line level. Without it, the signal is weak and noisy. Example of bypassing the preamp in mixer is that if you plug the musical instrument (such as a microphone) to a line input instead of the XLR microphone preamp input.
Solution: Do not plug instrument level signals (those coming from guitar) and microphone level signals without passing through a pre-amp. In a mixer, common mistake is to use the TS/TRS cable for microphone and plug it directly into the line input instead of the XLR microphone balanced input. Always use XLR connectors for connecting microphones to the mixer. This applies for both dynamic and condenser microphones. For optimal guitar direct recording, use a direct box then plug the XLR output of the direct box to the XLR input (microphone input) of the audio mixer or audio interface. Once you hooked up them correctly, applying gain in your preamp won’t add noise anymore because the recorded signal is very clean
5.) You are connecting the mixer main out to your PCI sound card line input. Your mixer main out is using professional audio line level while the PCI sound card line input is most likely using consumer line level voltages. A mismatch in voltages can result to noise, weak signal or distortion.
Solution: Instead of using an audio mixer to your computer, the best method would be to use an external audio interface (Firewire or USB) then connect that to your PC. No need to use an audio mixer or PCI soundcard.
6.) You are using noisy or broken cables.
Solution: Use standard and professional audio cables, shielded (this prevents electromagnetic interference) and much better –balanced cables, e.g. TRS plug or XLR.
7.) There is an impedance mismatch resulting to loss in signal; for example, plugging the low impedance microphone directly into an input with much lower impedance than the microphone.
Solution: Low impedance microphone inputs works well with high impedance inputs for maximum voltage transfer of microphone signal.
8.) Your equipment is not properly grounded. This can cause hum in your audio recording equipment.
Solution: Do not remove the ground in your power connectors; use them in connecting all of your recording equipment to the AC outlet.
9.) There is loose contact somewhere in your recording and playback chain.
Solution: Check for possibility of loose contacts and replace worn-out connectors.
10.) Noise in playback can occur if you have not muted line input or microphone input of the audio device or mixer. This is because of leakage noise from these sources.
Solution: Mute microphone inputs or turn their volume to zero.
11.) You are connecting the audio interface incorrectly to your studio monitors or to your PC.
Solution: Refer to your studio monitors for correct installation instructions and cabling guide.
12.) The musical instrument or recording equipment is a significant noise source itself. For example if you are using consumer grade equipment as compared to professional audio equipment, or using a noisy microphone or a defective recording gears.
Solution: Use pro-recording gear and equipment. For example use appropriate condenser microphones designed for recording studio applications and not your built-in laptop webcam microphone!
13.) Your recording signal level is very weak. If the signal is weak, the signal to noise ratio is very low and you have a noisy signal.
Solution: Record tracks at 24-bits, aiming for a maximum of -6dBFS and averaged around -15dBFS (rough guide) for best headroom and signal to noise ratio performance. Remember correct gain staging.
14.) If the control room is hot, the recording equipment would also heat up considerably producing noise and hiss.
Solution: Make sure your control and tracking room is adequately temperature controlled or well-ventilated against heat.
Content last updated on October 15, 2012