TUTORIAL - Cleaning Audio - Professional tools and how to's
Posted: 18 Jun 2016 13:30
I'm a professional in audio enhancement and editing with 20yrs experience both with music and forensic sound fields, I had a request to write a tutorial on how to clean audio like a pro with a few simple software tools.
I will start today with the tool kit required and over the coming days explain how to use them and produce a clean enhanced recording from that dirty hissy cell phone recording.
I will cover the following common issues, removing traffic or weather noise, removing (or at least reducing) music and tv noise, removing noise created from mains electrical interference "hum" such as air conditioning units, how to use a spectral analyser and graphic equaliser to reduce or isolate sounds, various methods to digitally increase the volume of an audio file based on the type of background noise, and anything else i think of along the way.
Part 1 - Professional Software
All methods i will describe are using 1 piece of software and 1 plugin with various utilities, to buy they are expensive, without condoning software piracy everything I mention here can be found by typing the name into google followed by the word to**ent.
Steinberg Wavelab - This is the interface for all of our work, wavelab is a professional editing and mastering package that is used to produce many of the songs you hear on the radio, tv audio tracks and dolby surround sound for theaters. Wavelab supports a plugin system used by recording studios for special effects, synthesizers, audio tools etc. we will be using the editing and analysis features of wavelab combined with a plugin tool kit called "izotope RX Tools"
So you just installed wavelab, you run the installer for Izotope RX, congratulations you now have a pro quality audio forensics lab.
When you open the program it will present you with 2 panes top and bottom of the screen you can drag a file into thew top pane, the top pane is your play window, the bottom is your file overview, both display the recording in the form of a wave where you can see increases and decreases in volume.
Open your first audio file in wavelab mp3s are decoded to wav format on first opening this can take some time - a 15hr 192kbps mp3 will take around 12 minutes to open and requires at least 2GB of free hard drive space on your PC for the temporary files. now we have our first recording in the editing window you will see if the file is over 10 minutes long the time gradients of the window are in 10 minute increments which makes it very hard to visually spot anything, in the bottom right of the top pane you will see a horizontal slider, moving this will increase or decrease the length of time displayed in the top pane, click this until you see the markers change from 10 minute resolution to 1 minute, this gives you a display where 1 minute takes up about an inch of horizontal screen space so you can see the audio events well enough but still have about 15 minutes across the entire screen the full resolution extends from microseconds displayed per inch thru to many hours per inch. to the right of the horizontal time slider we have the "amplitude" resolution ie the volume resolution, if your recording is very quiet as you increase the resolution you will see the waveform start to show you the hidden quiet sounds.
Part 2 - Basic increases of volume where there is little background noise:
Theory First - If the loudest noise in your recording is minus 15Db and we add 5Db gain we get a maximum level of minus 10Db, in any audio editing be it music, tv, film or love songs for adults our goal is to get the loudest noise on the recording as close to 0Db as possible, above 0 will start to distort sounds, most of the tools we will use have settings in the scale of decibels so it's a term and theory you need to understand.
if your recording is just a little quiet the quickest thing you can do is to use one of wavelabs built in tools. Click on the menu with the heading "process" then select "change level" here you will be asked to supply a number in decibels which will be the amount of gain will be applied, enter 5db i find this is a sensible amount to start with, click apply, and you will see the waveform displayed just got a whole lot chunkier on the vertical axis, review the audio if it is still quiet you should still see the gain increase window and you can click apply as many times as you like until things become audible. You will notice that the more you increase the gain the more hiss starts to appear if a cheap / low quality recorder / phone was used don't worry about this i will cover it's removal in a later installment of this tutorial, i regularly clean up recordings from 10yr old telephones to a reasonably good quality output file.
Enough for today if your following get your software installed, familiarise yourself with the wavelab interface and boost the volume of your first recording. more in the following days.....
I will start today with the tool kit required and over the coming days explain how to use them and produce a clean enhanced recording from that dirty hissy cell phone recording.
I will cover the following common issues, removing traffic or weather noise, removing (or at least reducing) music and tv noise, removing noise created from mains electrical interference "hum" such as air conditioning units, how to use a spectral analyser and graphic equaliser to reduce or isolate sounds, various methods to digitally increase the volume of an audio file based on the type of background noise, and anything else i think of along the way.
Part 1 - Professional Software
All methods i will describe are using 1 piece of software and 1 plugin with various utilities, to buy they are expensive, without condoning software piracy everything I mention here can be found by typing the name into google followed by the word to**ent.
Steinberg Wavelab - This is the interface for all of our work, wavelab is a professional editing and mastering package that is used to produce many of the songs you hear on the radio, tv audio tracks and dolby surround sound for theaters. Wavelab supports a plugin system used by recording studios for special effects, synthesizers, audio tools etc. we will be using the editing and analysis features of wavelab combined with a plugin tool kit called "izotope RX Tools"
So you just installed wavelab, you run the installer for Izotope RX, congratulations you now have a pro quality audio forensics lab.
When you open the program it will present you with 2 panes top and bottom of the screen you can drag a file into thew top pane, the top pane is your play window, the bottom is your file overview, both display the recording in the form of a wave where you can see increases and decreases in volume.
Open your first audio file in wavelab mp3s are decoded to wav format on first opening this can take some time - a 15hr 192kbps mp3 will take around 12 minutes to open and requires at least 2GB of free hard drive space on your PC for the temporary files. now we have our first recording in the editing window you will see if the file is over 10 minutes long the time gradients of the window are in 10 minute increments which makes it very hard to visually spot anything, in the bottom right of the top pane you will see a horizontal slider, moving this will increase or decrease the length of time displayed in the top pane, click this until you see the markers change from 10 minute resolution to 1 minute, this gives you a display where 1 minute takes up about an inch of horizontal screen space so you can see the audio events well enough but still have about 15 minutes across the entire screen the full resolution extends from microseconds displayed per inch thru to many hours per inch. to the right of the horizontal time slider we have the "amplitude" resolution ie the volume resolution, if your recording is very quiet as you increase the resolution you will see the waveform start to show you the hidden quiet sounds.
Part 2 - Basic increases of volume where there is little background noise:
Theory First - If the loudest noise in your recording is minus 15Db and we add 5Db gain we get a maximum level of minus 10Db, in any audio editing be it music, tv, film or love songs for adults our goal is to get the loudest noise on the recording as close to 0Db as possible, above 0 will start to distort sounds, most of the tools we will use have settings in the scale of decibels so it's a term and theory you need to understand.
if your recording is just a little quiet the quickest thing you can do is to use one of wavelabs built in tools. Click on the menu with the heading "process" then select "change level" here you will be asked to supply a number in decibels which will be the amount of gain will be applied, enter 5db i find this is a sensible amount to start with, click apply, and you will see the waveform displayed just got a whole lot chunkier on the vertical axis, review the audio if it is still quiet you should still see the gain increase window and you can click apply as many times as you like until things become audible. You will notice that the more you increase the gain the more hiss starts to appear if a cheap / low quality recorder / phone was used don't worry about this i will cover it's removal in a later installment of this tutorial, i regularly clean up recordings from 10yr old telephones to a reasonably good quality output file.
Enough for today if your following get your software installed, familiarise yourself with the wavelab interface and boost the volume of your first recording. more in the following days.....