How do I remove unwanted audio noise?

Audio noise can be defined as any unwanted or unpleasant sound that interferes with the clarity and quality of an audio recording or transmission. It can come from a variety of sources both internal and external to the recording equipment. Common sources include background chatter, computer fans, HVAC systems, electrical interference, poorly isolated microphone inputs, and more.

Noise can be problematic for a few key reasons. First, it obscures the intended audio content, making voices, instruments, and other sounds more difficult to discern. This leads to listener fatigue and poor intelligibility. Second, noise reduces the accuracy of many audio analysis and processing algorithms that rely on clean signals. This can degrade the performance of applications like speech recognition, audio forensics, hearing aids, and more. Finally, excessive noise makes achieving high fidelity reproduction more challenging. It limits the dynamic range, masks subtle details, and reduces the ability to localize sounds [1].

Therefore, mitigating and removing unwanted noise is an essential step in producing professional, intelligible, and pleasant sounding audio. The following sections explore different strategies and techniques for effectively removing or minimizing noise from recordings and live audio.

[1] https://www.cdc.gov/nceh/hearing_loss/public_health_scientific_info.html

Identify the Source of the Noise

The first step in removing unwanted audio noise is to identify the source. Here are some of the most common causes of audio noise:

• Background sounds – Fans, air conditioning, outside traffic can all get picked up by microphones and cause unwanted noise. Try turning off any background devices and move to a quieter recording environment.
• Microphone placement – If the microphone is too close to or pointed at the noise source, it will pick it up more. Position the mic closer to the desired audio source.
• Electrical interference – Nearby electronics like lamps, cell phones, or computers can emit electromagnetic frequencies that produce noise. Move mics farther away from electronics.

Testing recordings with the noise sources on and off can help pinpoint the cause. Getting the microphone as close as possible to the desired sound source while positioning it far from noise sources helps reduce contamination.

Adjust Your Microphone Settings

One of the easiest ways to reduce background noise is by adjusting your microphone settings. Here are some key settings to focus on:

Proper Gain Staging

Gain staging refers to setting the optimal signal level at each stage of your audio chain. Start by setting the gain on your microphone preamp or audio interface so your voice peaks around -12dB to -6dB. Going above -6dB can introduce clipping and distortion. Having proper gain staging gives your audio more headroom and dynamic range to work with.

Noise Gate Threshold

A noise gate mutes signals below a set threshold. Adjust the threshold so it mutes any constant background noise but doesn’t cut off your speech. The threshold should be set just above the noise floor. This eliminates distracting room tone and hum when you’re not speaking.

Sample Rate

Higher sample rates like 96kHz capture more frequencies, including inaudible high frequencies that can introduce noise. For speech, 44.1kHz or 48kHz is ideal. Excessive sampling rates just take up disk space without improving quality.

Getting these microphone settings tuned properly goes a long way in reducing unwanted background noise in your recordings.

Use Noise Suppression Software

There are two main options for using software to suppress unwanted audio noise – real-time and post-production. Real-time options process the audio as it’s being captured, before it’s recorded. This allows you to hear the noise reduction in real-time but is generally limited in capability. Post-production software analyzes a completed recording and allows for more advanced noise reduction since it can utilize the entire audio track.

Some leading real-time options include Krisp and RNNoise. Krisp uses AI to detect ambient noise and suppress it, even allowing you to tweak the noise cancellation levels. RNNoise is an open source option that implements noise suppression through deep learning algorithms.

For post-production, top choices include Audacity, Ocenaudio, and iZotope RX. Audacity is free, open source software with noise reduction features like noise profiles and multiband filtering. Ocenaudio also utilizes noise profiles and parametric equalization. iZotope RX offers advanced modules for finely targeted noise removal.

Equalize to Minimize Noise Frequencies

One effective technique for removing unwanted audio noise is to use an equalizer to identify and lower the frequency bands where the noise occurs. An equalizer allows you to boost or attenuate specific frequency ranges independently. By lowering the gain on bands where noise is present, you can reduce the audibility and impact of the noise while leaving the rest of the audio untouched.

To do this, play back the audio and open the equalizer on your system or DAW. As you listen, sweep through the frequency bands while narrowing the Q/bandwidth to pinpoint the exact frequencies where noise is most noticeable. Lower the gain of those frequency bands by 3-6 dB to diminish the noise. Be careful not to cut too much, which could make the audio sound thin or hollow. A subtle, targeted cut is often all that’s needed.

This technique is especially effective for consistent background noise like hiss or hum. However, it can also minimize intermittent noises that mainly occupy certain frequencies. Just be aware that extreme boosts or cuts could imbalance the frequency spectrum. When possible, make narrow, surgical EQ moves rather than wide, sweeping changes.

For more detailed advice, see this guide on using EQ to remove noise: https://soundshockaudio.com/how-to-eq-out-white-noise/

Noise Profile Capturing

Capturing a noise profile is one of the most effective ways to eliminate consistent background noise from audio recordings. This technique involves sampling a section of the unwanted background noise without any speech or other audio present. The noise profile is then used to ‘subtract’ the background noise from the rest of the recording.

Noise profile capturing works well for constant, steady noise like hum, hiss or a fan. To capture the profile, first make a recording with just the background noise, without any talking. This sample should be at least a few seconds long. Next, select the noise-only section in your audio editor and generate a noise profile or noise print based on this selection. Many programs like Audacity or Adobe Audition have dedicated tools for this.

Once the noise profile is created, you can apply it to the rest of the recording to subtract that same background noise. The profile essentially provides a fingerprint of the noise that can be removed while leaving the speech intact. This produces clean, noise-reduced audio with minimal artifacts. Just be sure to resample the background noise each time the acoustic environment changes.

Noise Reduction Plugins

One of the most effective ways to remove unwanted audio noise is by using dedicated noise reduction plugins. Popular options include Izotope RX, Waves X-Noise, and Sonnox DeNoise.

Izotope RX (https://www.izotope.com/en/products/rx.html) is considered the industry standard for audio repair and noise reduction. It includes modules like De-noise, De-click, and De-hum that can target and reduce specific noise issues.

Waves X-Noise (https://www.waves.com/plugins/x-noise)can analyze your audio and build noise profiles to eliminate steady broadband noise. It also features attack and release controls to finetune the noise reduction.

Sonnox DeNoise (https://www.sonnoxplugins.com/pub/plugins/products/denoise.htm) provides adaptive algorithms that continuously adjust based on your audio. It has a simple interface but can effectively reduce hiss, rumble, and other noise.

The advantage of dedicated noise reduction plugins is they offer advanced tools optimized to target and reduce specific noise issues without compromising the rest of the audio. They may require more learning but can produce cleaner results than basic filters.

Physical Acoustic Treatment

One of the most effective ways to remove unwanted audio noise is through physical acoustic treatment of your recording space. This involves adding sound-absorbing and sound-isolating materials to the room to prevent audio reflections and block exterior noise.

Soundproofing panels made of dense materials like mass loaded vinyl or acoustic foam can be mounted on walls and ceilings to absorb audio reflections that might otherwise bounce around the room. Placing these panels at reflection points and corners is key. According to A Beginner’s Guide To Acoustic Treatment, foam and mineral wool panels “soak up” sound energy to reduce unwanted reverb and noise.

For blocking exterior noise, isolation booths created from thick sound-blocking materials can provide an acoustic sanctuary for recording. Portable vocal booths made from sound-absorbing materials are also available. Placing the booth in a corner of the room can further enhance noise isolation.

Proper Microphone Technique

One of the easiest and most effective ways to minimize unwanted audio noise is by using proper microphone technique. This involves optimizing the distance, angle, breath control, and shielding when recording audio.

First, maintain an optimal distance from the microphone – generally 4-12 inches away depending on the mic. Get too close and you increase breath noise and pops. Too far and the audio quality diminishes. Experiment to find the ideal distance for your voice and mic.

Second, position the microphone at an angle, pointed across your mouth rather than directly at it. This prevents air blasting the mic on plosive sounds like “p” and “b.” A 45 degree angle off center is recommended, though anywhere from 30-90 degrees can work.

Third, practice proper breath control by breathing steadily through your nose. This reduces vocal ticks, lip smacks, and other mouth noises transmitted through breathing directly on the mic.

Fourth, use acoustic shielding like mic filters or booths to block incidental noises around you. Portable shields that mount on the mic stand help absorb ambient room tone and reflections.

With good mic technique – optimal distance, angled position, quiet breathing, and acoustic shielding – you can significantly minimize unwanted noise in your audio recordings.

When to Seek Professional Help

For persistent, complex, or high-quality audio issues that you can’t resolve on your own, it may be time to seek help from an audio professional such as:

• An acoustical consultant to analyze your room and make acoustic treatment recommendations (https://www.enoisecontrol.com/when-to-hire-an-acoustical-consultant/)
• An audio engineer to properly set up and tune your equipment (https://www.channelaudiogroup.com/single-post/do-i-really-need-an-audio-engineer-at-my-event)
• A freelance sound engineer to troubleshoot and fix complex audio issues (https://www.peopleperhour.com/discover/guides/hiring-a-freelance-sound-engineer/)

Seeking professional help can save you time and frustration compared to struggling with hard-to-solve audio problems. Their specialized skills, equipment, and experience can help identify and address the root causes of unwanted noise in your recordings or environment.