Restoring Audio with Izotope RX™ Izotope with Nat Johnson
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Restoring Audio with iZotope RX™ iZotope with Nat Johnson Tools, tips and techniques. © 2008 iZotope, Inc. All rights reserved. iZotope and iZotope RX are either registered trademarks or trademarks of iZotope, Inc. in the United States and/or other countries. Other product or company names mentioned herein may be the trademarks of their respective owners. INTRODUCTION ..................................................................................................4 Intended Audience for This Guide .................................................................................. 4 WHAT IS AUDIO RESTORATION?......................................................................5 What are the Goals of Good Audio Restoration?........................................................... 5 WHAT IS IZOTOPE RX? ......................................................................................7 GETTING SET UP TO RESTORE AUDIO ...........................................................8 Equipment.......................................................................................................................8 Transferring media to the computer ............................................................................ 10 Recording from analog formats.................................................................................... 10 SUGGESTIONS FOR THE RESTORATION PROCESS....................................13 HOW TO IDENTIFY AUDIO PROBLEMS...........................................................14 Using the Spectrogram and Waveform Display............................................................ 14 How to Spot Audio Problems........................................................................................ 17 Changing Spectrogram Settings.................................................................................... 21 BROADBAND NOISE REDUCTION...................................................................24 What is Broadband Noise? ........................................................................................... 24 Basic Techniques for using RX’s Denoiser..................................................................... 24 HUM AND TONAL NOISE ..................................................................................31 Finding and Removing Hum.......................................................................................... 31 Using Denoiser for Tonal Noise Removal ..................................................................... 35 REMOVING CLIPPING.......................................................................................36 How does RX’s Declipper work? ................................................................................... 36 Repairing Clipping ......................................................................................................... 36 REMOVING CLICKS AND POPS.......................................................................39 Using RX’s Declicker...................................................................................................... 39 REMOVING INTERMITTENT NOISES AND GAPS ...........................................43 Using RX Spectral Repair............................................................................................... 45 GENERAL RX TOOLS........................................................................................47 Comparing Settings....................................................................................................... 47 Batch Processing ........................................................................................................... 48 EQ and Gain .................................................................................................................. 49 Working with Presets.................................................................................................... 50 Keyboard Shortcuts and assigning your own................................................................ 51 Restoring Audio with iZotope RX™ Page 2 of 74 ©2008 iZotope, Inc. EXPORTING AND DELIVERING AUDIO ........................................................52 iZotope MBIT+™ Dithering Panel (RX Advanced only).................................................. 54 iZotope 64‐Bit SRC™ Panel (RX Advanced Only)........................................................... 56 SUMMARY .........................................................................................................58 APPENDIX: REPAIRING THE INCLUDED AUDIO FILES.............................60 Example 1: Removing Broadband Noise from a Concert Recording ............................ 61 Example 2: Using Denoiser and EQ on a Shellac Recording of Spoken Word .............. 63 Example 3: Restoring an Historical Speech: Making Voice More Intelligible.............. 64 Example 4: Cleaning up a Phone Interview with Spectral Repair................................. 65 Example 5: Removing Clicks and Pops from a Concert on Record ............................... 67 Example 6: Removing Clipping from a Phone Interview .............................................. 69 Example 7: Removing Guitar String Squeaks with Spectral Repair .............................. 71 Example 8: Filling a Gap in Audio with Spectral Repair................................................ 73 Restoring Audio with iZotope RX™ Page 3 of 74 ©2008 iZotope, Inc. INTRODUCTION Today, audio and video recordings can be made by nearly anyone. From the simple camcorder to sophisticated studios and sound stages, a growing number of recordings are produced daily. And as our world becomes increasingly and audibly congested, so the rate of ruined recordings is rising! Human error, unexpected electrical or mechanical interference and unwelcome intrusions from aircraft, cell phones, pets, people and Mother Nature regularly impact even the most seasoned professional. Whether you’re a professional or just getting started, you have probably run into difficult audio situations like this and wished you could correct what seemed like an impossible dilemma. The purpose of this guide is to help you develop practical and effective ways to remove noise and fix audio problems using iZotope RX™. We hope this guide will help you understand the basics (and beyond) of audio restoration and help you to apply them to your own projects. Intended Audience for This Guide • If you don’t know anything about audio restoration and don’t have iZotope RX, we still hope this guide will help you. Feel free to download the trial version of RX to follow along and try out these concepts for yourself. • If you don’t understand audio restoration but do have RX, you’re in luck. RX gives you a complete range of audio restoration tools and this guide shows you how to use them. • If you have RX and know the basics of restoring audio, this guide will still show you tricks or techniques that are possible in RX. Just say “yeah, I knew that” when appropriate for the other parts. Try It For Yourself! Be sure to download our RX Restoration Guide audio examples and try your hand at restoring them. At the end of this guide you’ll find an Appendix that will walk you through how to do the repairs. It’s a great way to apply what you’ll learn from reading this guide. Restoring Audio with iZotope RX™ Page 4 of 74 ©2008 iZotope, Inc. WHAT IS AUDIO RESTORATION? Audio restoration is the process of removing noise and other imperfections from sound recordings. Audio restoration can address problems including: • ambient background noise, including fans, air‐conditioners and heating systems • electrically‐generated interference like buzz from fluorescent lights • hum from bad ground connections or induced from power sources • background hiss from reel‐to‐reel tape, audio and video cassettes • surface ticks and pops from vinyl, shellac 78 or other phonograph recordings • audience noise including coughs, pagers and cell phones • overload distortion (or clipping) When you hear the word “restoration,” you might be inclined to think of dusty vaults filled with aging master tapes and records. Of course, audio restoration includes taking old recordings and reviving them, but it is hardly limited to antiquity. Every time you switch on a USB recorder, camcorder, digital camera, voice recorder, or cell phone you may encounter a variety of unexpected and unwelcome audio “guests.” For example, we recently read a review of a concert pianist whose debut at Carnegie Hall was marred by the ringing of a cell phone. The reviewer assumed that,” this and other intrusions will no doubt be magically erased when this concert is issued on CD.” While there is no magic button for removing cell phone noise (yet), the latest generation of audio restoration tools like RX can be just as useful for cleaning up 21st century problems as they are for restoring the earliest phonograph recordings. What are the Goals of Good Audio Restoration? The goal of good audio restoration is to render the best possible sound with the least audible human intrusion. In essence, your intervention in the original recording should be transparent and not introduce new artifacts that distract the listener. It’s useful to remember that no recording is truly perfect. What we hear in playback, no matter how well recorded originally, represents only a facsimile of the actual audio event. In the early 1980’s, when compact‐disc players became readily available and affordable, commercial tape vaults turned into gold mines. But strangely, during the early days of CD restoration,