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I would like to ask for help please. I don’t have an experience in sounds or recording or filtering. I have a voice record of two speaking with lots of background noise due to an instrument that was in the same room and due to a big freezer. I can’t hear the voices clearly. Anyone who have experience here who can help or can do a filtering for the voices ? It is just 6 minutes record. I don’t know how to do it or how much technology needed for it.
Thanks so much
There are several ways you could approach this, and you will likely need to use a mixture of different techniques to get the best result.
This sounds like an exercise in forensics rather than a quest for clean audio so some of the solutions offered here may not be of any use
If you can't hear the voices because the background noise is too loud or because the background noise is in the same frequency band as the voices, there is a strong probability that you will not be able to recover anything more intelligible than you already have.
Low-Pass/High-Pass Filters
Low-pass filters are designed to only let audio below a set frequency through to the listener - these are great for removing high-frequency hissing noises.
Similarly, high-pass filters only let audio above a set frequency through to the listener - these are great for removing low-frequency rumbles.
Notch Filter
Notch filters are useful for removing a specific band of frequencies. These can be very useful for lessening things like electrical interference, wind noise, rumbling or other band-specific sounds.
Dynamic EQ
A dynamic EQ will react to both frequency and volume to boost or cut specific frequency ranges. They can be fine-tuned to a very precise degree and, as they're dynamic, they're great for trying to zero in on moving targets like human voices.
Noise Gate
A noise gate measures the volume of incoming audio and only lets it through if it's loud enough. This should help to get rid of some of the background noise when the voices are not sounding.
Audio Spectrogrametry/Sonographics
Spectrograms are a way of visualising changes within a whole range of frequencies over time. You get a 'heat-map' style image of the frequencies in your audio - this can be extremely useful in identifying which frequencies should be cut and when.
A note about Frequency Ranges
Human voices sit between around 0.5kHz to 9kHz with intelligibility working in the 2kHz to 4kHz range. The actual ranges involved will be smaller but their bounds depend on who is talking - male or female, adult or child.
You will need to pay special attention to any audio in these bands - cutting too much will reduce intelligibility.
Most, if not all of these tools, are available built into free audio editing software such as Audacity or can be found as free plugins.
I would start by removing anything outside those frequencies - use a low-pass filter to cut everything above 9kHz and a high-pass filter to cut everything below 0.5kHz - This removes everything that is definitely not a voice. Then have a look at a spectrogram of what you have left and figure out if you can use a gate and where you might be able to use notch filters and/or EQ.
Getting something intelligible back is going to take a lot of work. Getting something clean back is likely to be impossible.
Use a Limiter, "Filtering" in Particular is mostly connected to a EQ, which wont realy help you here (except u literally now which frequencies are hussling).
These are the Problems/ Thougts.
Voice Loud, Little Background Noise (Maybe a Chair or a Fan) : Use a Limiter, Its Threshold has to be around the middle of the Loudness of your Voice. So that there wont be ANY clipping of your Voice, basicly search for the spot where "only" the noise is in the treshhold. Gain to 0 basicly everything under the treshhold (u just set it to only noise) is muted i would set the Release to about 20-50 (so you have a bit of a fade and no hard clips)
Voices Loud, Realy Loud Noise : This will be the Problem. If your Noise is in the same Audiotrack as the Voice (which i presume) and the noise is as loud (50%/60% is a huge thing) you will have to use a EQ. Filter / Search for the frequencies where the voice is loud/present will be mostly in the mids/ highs (lowend mostly will be noise) and cut them out. If u have access to a strong MultibandCompressor as the FabFilter Pro-MB or an Dynamic EQ as FabFilter Pro-Q3 or TDR Nova. U could scan for where x frequencies are noisy and turn them down except for when it exceeds a certain treshhold (maybe voice) and turn it up.
TL:DR If u have a simple bad microphone and there is some noise (tolerable noise) inside the audio file. Try a Limiter an set the Threshhold to the low noise.
If u have extreme loud noise (in which case if u wanna use it re-record it, i take this here as a "safe the audio" case) try to filter it out. This scenario will only be interesting if its maybe some unrecreateable audio (oldschool samples/ etc.) to save it. If u have a bad audio and are able to fix stuff with recording, do it.
last quick tip. If u wanna do music with it, most of the time after basic processing (EQ/DS/MB) there wont be any noticable noise. some reeverbs could just make it unhearable or even get some ambiente going.
I hope i could help you ! come again for questions
Try Audacity and its noise remover :
https://filmstro.com/blog/how-to-remove-background-noise-in-audacity
