October 4, 2007

Digitizing records and tapes with Audacity

Author: Beth Skwarecki

You've been ripping CDs for years, but what about those dusty cassette tapes
in your attic and all that bargain-basement vinyl at used book sales? With
Audacity, you can capture those vintage tunes, clean up their sound, and
carry them around on your MP3 player.

Audacity is a powerful free cross-platform audio editor. It includes tools such as noise removal filters and automatic track splitting that can speed up the process of turning your antique audio into shiny new MP3s or Oggs.

All you need to begin, besides a recent download of Audacity, is a computer with a sound card -- use the "line in" port if you have one -- and your tape deck or turntable.

Plugging in

You can plug a tape deck directly into your sound card, but a turntable requires a phono pre-amp. The pre-amp amplifies the sound to a useful level, and applies the RIAA equalization curve, which is necessary for records made after 1954 or so. (For older records, apply a different equalization curve using these directions.)

A USB turntable (I use the ION iTTUSB) can plug directly into your USB port. It has the pre-amp's functions built-in.

To begin recording with Audacity, check that you have your computer's recording and playback devices listed under Edit -> Preferences -> Audio I/O. Then just press the big red Record button. When you're done, press the yellow Stop button. Your recording now appears as a waveform on your screen, but it's not saved to disk. Click File -> Save to save it as an Audacity project (.aup). You'll need to process this raw recording to make finished song files.

If you prefer to do the recording and processing in separate batches -- a good strategy if you're borrowing time on a friend's turntable -- you can use your favorite recording tool (such as arecord) to create a WAV file of each record or tape side. When you're ready to process and split the tracks, just import the WAV with File -> Open. Audacity will detect the file type and convert it into an Audacity project (.aup).

Automagic track splitting

If your recording is part of an album, it will have short silences between the tracks. Audacity can detect those silences and place markers to split the tracks. Here's how.

Select your whole recording by pressing Ctrl-A and click Analyze -> Silence Finder. Audacity will create a label track underneath your main audio track, with a marker at every silent spot.

You'll want to delete the last label, because it's only marking a split-second of silence. To delete it, click on the label and press the backspace key until the label disappears.

Now you've got a label for each track, but they're all called something unhelpful, like "S." Click on the first label. This sets the playback position, so you can begin listening to the track, and it also gives focus to the label so you can type in the title of the song. (When you export to MP3, the label text becomes the ID3 Title tag.)

Because the titles will become filenames later, avoid using the slash (/) character, since that's illegal in a Unix filename, so Audacity won't be able to save a file with a slash in it. If two labels have the same title, Audacity will add numbers to their filenames -- so if you have two tracks named Song, your finished mp3 files would be named Song-1.mp3 and Song-2.mp3.

Manual track splitting

If your recording doesn't have clear silences between the tracks, the Silence Finder can't help you. Recordings of radio shows usually have this problem, because DJs try to avoid dead air. (When I tried the silence finder on a radio broadcast, my labels marked awkward pauses in DJ patter and musical breaks in the middle of songs.)

Manual track splitting requires more patience than the automatic sort, but it's not hard. First, create a new label track with Tracks -> Add New -> Label Track . Listen to your recording using the playback and navigation tools, and click Pause at the point where you'd like to start a new track. Place a label there with Tracks -> Add label at playback position (Ctrl-M). Click inside the label to give it a name, as before.

Filtering with the Effect menu

If your recording has a constant background noise, such as hiss from a cassette tape, you can remove it with the Noise Removal filter. It's a two-step process:

First, select a few seconds of silence, say from the beginning or end of your recording. Click Effect -> Noise Removal, and click "Get Noise Profile."

Then, select all (Ctrl-A) and click Effect -> Noise Removal again. You can adjust the parameters and listen to a preview before hitting the Remove Noise button to finish the job. (If the preview is too short for your liking, adjust the preview length in Edit -> Preferences -> Audio I/O.)

When a record needle hits a speck of dust, it creates a "click" or "pop" on a recording. Audacity has a filter for this, too. Select all and use Effect -> Click Removal. You may need to experiment with the settings to find what works best for your recording.

Exporting and tagging

Before you export your Audacity project into a folder of MP3s or Oggs, you'll want to fill in the metadata for ID3 or Ogg tags. Click File -> Open Metadata Editor and you can enter the artist, album, year, genre, and comments. Leave the title and track number blank; Audacity will fill these in from your labels.

When you're ready to go, click File -> Export Multiple. Set the export format to MP3, or the format of your choice. (Note that you need to have lame installed to encode MP3s.) Enter the name of a convenient directory as the export location. In the same dialog, tell Audacity to split files based on labels, and to name files using label name. Click the Export button, and you're done!

In addition to exporting individual songs, you might want to save your whole Audacity project in case you want to return to it, say to do more effects filtering on the whole album. In that case, choose File -> Save Project.

If you want to edit your MP3 tags, you don't need to do it in Audacity and re-export the files. You can use the id3v2 tool to edit MP3 tags from the command line, or try EasyTAG for a point-and-click interface to edit the tags in MP3s or Oggs.

To learn more about what Audacity can do (and it can do a lot!), peruse the Audacity wiki.

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