From Digital Audio Recording to Audio CD: Part 2 - Basic Audio Edits

Audacity Logo The Audacity how-to continues!! This second part of the series involves working in Audacity to edit your audio file.

A major sound edit technique: Changing Amplification (making a quiet recording louder).

This multi-part how-to series focuses on using Audacity and iTunes – two freely available pieces of software – to work with your recording and then create an audio CD.

Part 1:  Getting your audio into Audacity, whether by opening a digital audio recording made elsewhere, or using Audacity to record directly to your computer.
Part 2: (You are here!)Making minor edits to increase sound level.
Part 3: Exporting your recording to a file format that iTunes can use and creating an Audio CD.
Part 4: Dividing the audio into sections based on topics of discussion using Audacity’s Label Tracks.
(note: I may expand sections if any one of them gets to be too long. This section will be updated as I go.)

Amplifying audio

Here is a stereo file recorded using my portable-studio-in-an-Otter Box (described here).


image
(click to enlarge)

Notice that the waveforms are small and don’t take up to the entire vertical space there. The recording quality is clean enough where I can amplify the audio.

(The goal in recording is to create a recording with all those sound levels present to begin with. But when that hasn’t happened, you can amplify the sound you have.)

Compare these next two waveforms. One is from the above-mentioned recording. It is small: it does not occupy all of the vertical space allowed for the waveform. Another one was made under better conditions, with a hand-held microphone closer to the speakers’ mouths. It’s taller, overall: some portions of waveform occupy the entire vertical area of the audio track.

image
(Click to enlarge)

I put both of them side by side here in this audio track (I changed the second one from mono to stereo). And here’s a shout out to Sheri Fenley, whose dulcet tones you can hear in the second half of the movie’s audio track.)

Warning:  If you attemt to turn up volume to hear the first part, you will be blown away by the sound of the second excerpt. Total time: under 13 seconds.

[note: if you are reading this using a feed reader (Google Reader, Feed Demon, Bloglines, NewsGator, Net News Wire, Cyndicate, NewsCrawler, etc.), the above movie will not appear. Please click through and visit this actual post and view the movie. Have troubles viewing the movie? Please let me know in the comments.]

The quieter recording is cleanly enough done that it can be amplified. So that’s what I’ll demonstrate, here.

  1. From the menu, choose Edit > Select > All
    (or Command-A on MacOS or Ctrl+A on Windows and Linux.) See image.
    image (Click to enlarge)
  2. The background for the entire waveform is highlighted (darker).
    image (Click to enlarge)
  3. From the _________ menu select amplify.
    image (Click to enlarge)
  4. A dialog box appears, with numbers auto-generated for you.
    Audacity generates numbers to provide the maximum amplification without clipping the audio. (Sorry, won’t be discussing clipping here, other than to say it’s a technical term for maxing out the volume. I’ll take up the whole concept of clipping in more detail in a later post.)
    image (Click to enlarge)
  5. (optional) If you want to preview the sound after amplification, click the Preview button.
    A progress bar appears, and after it completes, a short segment of your audio plays.
    image (click to enlarge) 
  6. Satisfied with your settings? Click the OK button on the Amplify Preview dialog box.
    The dialog box disappears, and the Amplify progress bar appears.
    When the Amplify progress bar completes, the progress bar disappears and your audio waveform enlarges.
    image (Click to enlarge)
  7. Click the Play button on Audacity’s Control Toolbar to listen to your audio.

An Advanced Amplification Trick


Here’s a little bonus section on amplification. Looking over the entire waveform, the peaks could  be larger.  We just amplified this audio track. Why is the overall waveform still medium and not large?

When you select the entire audio track and amplify, Audacity looks at the loudest part of the file (called, in audio-technicalese, the peak), and makes a calculation—how much do I need to amplify this in order for the peak to reach maximum? And that’s where the 11.8 number came from.

But what if the loudest part of the audio is much, much louder than the rest of the overall recording? What do you do then?

Find out what the loudest part is and isolate it and amplify the rest. For this particular file, I’ll show you what I did.

First, I needed to discover and isolate the loudest part. Here again is the entire audio file, with the loudest part circled in red.

image

Using the selection tool, I dragged a selection over that loud area. Then I zoomed into it, to see what it was. (This illustration shows the controls for the Selection Tool—the default tool, but still, it’s good to know where it is—and the control for Zooming In.

image

And here’s the selection, once it’s zoomed in. You can also adjust the width of the selection by dragging from the edge of the selection to expand or contract the selection.

Once you’ve made a selection, when you click the Play Button on the Toolbar, Audacity will play the selection only.

It turns out that this is a moment where the interviewee laughed. I decided to isolate the laugh. I adjusted the selection size to get only that laugh.

image

Once I had the selection made, I added a label for it. From the Tracks menu, I chose Add Label At Selection. (Keyboard shortcut: Command-B for MacOS and Ctrl+B for Windows)

image

Audacity added a new type of track in the project window, below the original audio track. The new track is called a label track. Once Audacity made the label, the cursor was placed inside the label, ready for me to type the label’s name. I typed the word “laugh” so I’d know what the selection was. (I’ll discuss more about labels in a later episode of this series.)


image

Now that the label was set, I wanted to see the entire audio track in the project window. To do that, I clicked the Fit Project button in the Edit Toolbar.

image

Audacity changed the view of the audio track so that the entire recording fit into the window.

Now that the label is there, I can use that to ensure I select everything else but the laugh in order to amplify everything else.

Watch this movie for the steps I took to amplify the audio.

[note: if you are reading this using a feed reader, the above movie will not appear. Please click through and visit this actual post and view the movie. Have troubles viewing the movie? Please let me know in the comments.]


Next up: Getting that recording into iTunes and burning a CD with it.

(Then I’ll go back and talk some more techniques for Audacity and labels and noise edits and the like)

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Posted by Susan A. Kitchens on April 30, 2010 in • AudioAudio: SoftwareHow-To
1 CommentsPermalink

« Previous From Digital Audio Recording to Audio CD: Part 1 - Audio into Audacity | From Digital Audio Recording to Audio CD: Part 3 - iTunes and CD burning Next »

Comments

OMG, you are amazing!  thank you for sharing your expertise with us.  This series is now part of my “how to"library.  Thank you again.

Joan Hill  on 05/05  at  07:55 AM

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