How do I reduce noise after recording?
Noise refers to any unwanted or interfering sounds that degrade the quality of an audio recording. It can include background sounds like traffic, air conditioning, computer fans, as well as artifacts introduced during the recording process like hiss, hum, clicks and pops. Reducing noise is critical for achieving clean, professional audio that effectively conveys the intended content.
Too much noise can obscure dialogue or musical detail, make voices harder to understand, and generally distract the listener. It introduces an element of chaos and muddiness into the audio. As this source notes, noise cancellation improves clarity and enhances the listening experience. Removing noise allows the core audio content to shine through in its purest form.
Use Noise Reduction Plugins
One of the most effective ways to reduce noise after recording is to use dedicated noise reduction plugins. Popular options include:
- Izotope RX – This professional audio repair toolkit includes the RX De-noise module, which uses spectral analysis to isolate and remove background noise. It offers advanced controls for fine-tuning noise reduction (https://audiosorcerer.com/post/noise-reduction-plugins/).
- Audition’s Noise Reduction – Adobe Audition comes with a capable noise reduction effect that can target steady broadband noise or isolated noises like clicks and pops (https://emastered.com/blog/free-noise-reduction-plugins).
- Waves X-Noise – Uses a pattern recognition algorithm to reduce noise based on a noise profile you capture. Good for removing constant background noise.
- Acon Digital DeNoise AI – An intelligent noise reduction plugin using artificial intelligence to separate noise from the actual audio content.
These plugins analyze the audio to isolate noise, allowing you to attenuate just the unwanted frequencies while preserving the important audio. They provide advanced controls to tweak the noise reduction amount and targeting.
Noise Gate
A noise gate is an audio plugin that silences audio below a set threshold or level. The gate is essentially closed to any sounds that do not reach the threshold level, blocking unwanted background noise from being recorded (Source: https://www.musicgateway.com/blog/how-to/what-is-a-noise-gate-how-do-you-use-it).
The key settings on a noise gate are the threshold and range. The threshold sets the level at which the gate opens to allow audio through. Any sounds below this level will be muted. The range setting determines how far the gate opens once the audio exceeds the threshold. A shorter range closes the gate more quickly after the sound dips below the threshold again.
Noise gates are very effective at removing constant background noise during quiet sections in your recording. Setting the threshold just above the level of the background noise will cut out the noise while allowing the intended sounds like vocals or instruments through. Noise gates require some experimentation to find the best threshold and range settings for your particular audio.
Use EQ to Reduce Noise Frequencies
One of the most effective ways to reduce background noise after recording is to use EQ cuts to remove unwanted frequency ranges that contain noise. For example, low frequency rumble below 100 Hz can often be reduced by applying a high pass filter around 100 Hz (according to EQ Frequencies from Songstuff). This will attenuate the low frequencies while allowing the important vocal and instrument ranges to pass through.
Similarly, a low shelf filter around 100-200 Hz can help reduce low frequency hum or rumble as well (per The 6 EQ Filters from Music Guy Mixing). High frequency hiss above 10 kHz can also be attenuated using a low pass filter around 10 kHz. Narrow notch filters can also be applied to precisely target and remove any narrow band resonances or tones.
When applying EQ for noise reduction, it’s generally best to make small cuts of only a few dB. Drastic filtering can negatively impact the tone. Listen critically and only apply as much filtering as needed to clean up the noise without compromising the signal quality. Targeting the correct frequencies for noise removal requires experience, so reference an EQ frequency chart for common instrument and vocal ranges.
Use a De-Esser
A de-esser is an audio plugin that can help reduce sibilance and high frequency noise when recording vocals or other sources.
Sibilance refers to excessive ‘ess’ and ‘shh’ sounds that can be harsh on recordings. De-essers work by detecting frequencies typical of sibilance (usually between 2-8 kHz) and compressing those frequencies specifically to smooth out the sound.
According to this article, de-essers apply gain reduction like a compressor to sibilance and other high frequencies to tame issues in the vocal track.
By targeting just the frequencies that cause sibilant noises, a de-esser can reduce harshness and noise without altering the rest of the vocal’s tone and quality. This makes them an effective tool for polishing recordings and removing distracting high frequency noise.
Reduce Noise in Quiet Sections
One way to reduce noise is to strip out the silent sections where there is just background noise and no vocals or instruments playing. Audacity and other audio editing software have tools to detect sections of silence and remove or truncate them.
For example, in Audacity you can select a section of audio and go to Effect > Silence Finder to detect silent passages. Then you can use the Truncate Silence feature (Effect > Truncate Silence) to strip out silences longer than a specified duration. Set the “Truncate to:” control to a short duration like 0.5 seconds. Then silences longer than that will be truncated down to the set threshold.
This is an effective way to get rid of noises like computer fans, air conditioning, or other steady ambient sounds in the quiet parts between words, notes, and phrases where there is no intentional audio. It helps clean up the recording and reduce the overall noise level. Just be careful not to set the Truncate Silence duration too short, or it may cut off the beginnings and ends of intentional sounds.
Rerecord in a Treated Space
One of the most effective ways to reduce noise when recording is to rerecord your audio in an acoustically treated space optimized for sound quality. This could be a professional recording studio designed for audio recording, or even a room in your home that you have treated to control reverberation, echo and background noise (Source 1).
Acoustic treatment involves adding sound-absorbing materials to walls, ceilings and floors in order to dampen unwanted reflections and ambient noise. Materials like acoustic foam panels, bass traps, absorptive curtains and rugs can significantly reduce reverb and background noises. Setting up a treated vocal booth or room for recording vocals, voiceovers or instruments can capture much cleaner audio.
The level of acoustic treatment needed depends on the existing conditions of the room as well as your budget. But even simple DIY acoustic panels made of rigid insulation or dense material covered in fabric can tame reflections. Every little bit of treatment helps capture cleaner, noise-reduced audio (Source 2).
Use a Pop Filter
A pop filter helps reduce noise like plosives and breathing picked up by the microphone. A pop filter is typically a mesh or perforated metal screen surrounded by an outer frame that is placed between the microphone and the audio source (typically vocals from a singer or speaker).
When a person vocalizes sounds that have fast air movement like “p”, “b”, “t”, etc. it can create sharp bursts of air that hit the microphone diaphragm abruptly and cause an audible popping or clipping sound. This is called a plosive. Pops can also occur from other mouth sounds like breathing, sibilance, and hard consonants.
The fine mesh or perforated metal of a pop filter diffuses these bursts of air and prevents them from directly hitting the microphone diaphragm. This smooths the waveform and negates the popping sounds. The result is cleaner audio and reduced distortion particularly on vocal recordings.
Pop filters are a simple but essential way to reduce undesirable noise and achieve broadcast quality recordings of vocals and voiceovers. They can be mounted on a microphone stand or boom arm near the microphone and allows performers to work closer to the mic without negatively impacting sound quality.
Proper Microphone Technique
One of the leading causes of excess noise is improper microphone placement and technique. The optimal distance for most mics is 3-12 inches between the microphone and your mouth to maintain a clear sound without picking up plosives or breath sounds (Source).
Avoid pointing the mic directly at your mouth, which can cause popping sounds. Instead, angle the microphone slightly off-axis at around 45 degrees. This allows some of the air pressure from plosives to dissipate without directly hitting the mic (Source).
Maintain good microphone technique by keeping a consistent distance and angle from the mic when speaking or singing to prevent unwanted fluctuation in volume or tone. Use a pop filter to help diffuse plosives if close mic’ing is required. With proper placement and technique, you can capture clean audio right from the source.
Conclusion
In conclusion, there are several effective ways to reduce noise after you’ve recorded audio or voice tracks. Using noise reduction plugins is one of the most common and effective methods. Plugins like iZotope RX enable you to target and reduce specific noise frequencies without damaging the original audio.
Noise gates can also help to automatically reduce background noise during quiet sections in your recording. Simply set the threshold level to duck the volume when you’re not actively speaking or performing.
It’s also important to use proper microphone technique while recording, including staying close to the mic, using a windscreen, and recording in an acoustically treated space when possible. Rerecording audio under better conditions is an underutilized way to significantly improve your recordings.
Following these tips will help you achieve clean, professional-sounding recordings with minimal distracting noise.
