How to Clean Up Audio Cassette Recordings and Convert to MP3 Using Free Software

Getting started

For the purposes of this article, we will assume that you have the knowledge to download install software to your computer from different website link. We will also assume you have some basic audio equipment knowledge, such as what an RCA jack is. Chances are you already have everything you need, other than the software. This tutorial will also assume that you’re using Windows XP, though all the software mentioned works on other platforms as well.

What you will need

PC, equipped with a soundcard that includes at least 1 stereo input.

Audacity (free audio editor/recorder) – http://audacity.sourceforge.net/

LAME mp3 library (mp3 codec) – http://www.free-codecs.com/download/Lame_Encoder.htm (if you already have some other means of encoding that you use, ignore this

Audio cassette deck

Some means of plugging the cassette deck into the soundcard – if it has RCA outputs, an RCA-to-1/8th -inch stereo adapter is available in most electronics stores.

Step 1: Connect  amp; setup Audacity

Ok, so you have downloaded and installed the necessary software. Now, connect the cassette deck to the soundcard, and we will begin the process of setting up Audacity for recording our audio.

Open Audacity, and under the Edit menu, go to Preferences. The first page that comes up should be “Audio I/O”. Make sure the proper inputs and outputs are selected for your sound card (should be something like MME: [soundcard driver name] or MME: Microsoft Sound Mapper). The input you want is the line-in, not the microphone input. Then, click on “Import / Export”, and click the Find Library button to point Audacity to your LAME codec. The location should be something like C:\WINDOWS\system32\lame_enc.dll. These two things should be the only options you really have to do anything with right away, so let’s hit OK and move on.

Before we actually record any audio for keeping, we want to set the input level from the cassette deck to avoid digital clipping, which results in the peaks of the loudest waveforms being cut off and can introduce nasty distortion. One way to do this is to find a portion of your source audio that represents the loudest signal it’s likely to produce, and play it back while monitoring the input. To do this, first press the Pause button in Audacity’s toolbar, then press the Record button (these buttons are known collectively as the “transport controls”). This will create a new track and allow you to monitor the level using the meter at the top left of the toolbar (the meter right next to it is for the output). For safety’s sake, you will want to make sure the loudest peaks come in a little under 0 (the loudest level possible).

Step 2: Begin recording

We are now ready to begin digitizing our cassette audio. If recording a two-sided tape, I like to do the recording in two passes, saving each as a WAV file along the way. If you have a cassette deck with auto-reverse, there’s nothing stopping you from recording one contiguous file, but I find it easier to work with the two shorter files later on in the process.

If you left Audacity on Pause, just press Pause again to begin recording, or press Record to begin recording immediately from a “stopped” state. With your cassette playing, let Audacity record until the end of the first side, and hit Stop. You will see a visual representation of the audio’s waveform- one each for the left and right sides of the stereo file. Double-click on one side to select the whole waveform. Now, go to the File menu and choose Export Selection. In the drop-down list for “Save as type”, choose “WAV, AIF, and other uncompressed types”. Click on the Options button, and under Format, choose “WAV (Microsoft 16 bit PCM)”. Choose a file name, and save your file. You may just hit OK on the following screen, as there’s no need to add metadata (tags) yet. Repeat the process for side 2 of your cassette. The reason we’re saving these files now is so we have something to come back to should we mess up the cleaning-up process later. You can always delete these files when you’re sure you don’t need them anymore.

Step 3: Noise removal

One of the great features of Audacity is the built-in Noise Removal effect, which we will now use to remove the tape hiss from our recordings.

In order for the effect to do its magic, we need a “noise profile”, which is essentially a sample of just the noise (in this case, tape hiss), so Audacity knows what to filter out. To do this, select a portion of the audio that contains only the noise, like a space between songs or the space at the beginning or end of the file- use the zoom tool (located between the meters and transport controls) if you need it to find a suitable selection. It only has to be a few seconds in length. Then, go to the Effect menu, choose Noise Removal, and click the Noise Profile button to capture the profile. The dialog will disappear. Now, select the entire waveform again (it’s the I-shaped tool if you did switch to zoom), and go back to the Noise Removal effect. There are three controls- Noise reduction controls how much filtering is applied, Frequency smoothing controls how the algorithm “sees” the different frequencies in the audio, and Attack/decay time controls how fast it reacts. You will probably need to try some different settings to see what works best, this is where the Undo function may come in handy. If you get carried away, you will notice what we call “artifacts”, which in this case usually show up as strange, high-pitched squelchy noises. What you want is a setting that removes as much noise as possible without taking too much of the high frequencies with it, or creating the dreaded artifacts I just mentioned. Start by leaving the reduction amount and Attack/decay time where they are, and moving the Frequency smoothing slider close to the center, or higher.

If you feel it needs it, you can add some high end back to your audio using the Equalization effect, which is like a more visual version of the equalizers you may have seen in-home or car audio setups

Step 4: Exporting individual files

This will be easiest if your audio has clearly-separated songs, with some space between tracks. If not, you’ll just have to decide what makes the best splitting point. In these cases, you will want to zoom in to make sure your split occurs on a “zero-crossing”- where the waveform crosses the middle line. Failure to do so may result in pops or clicks in your output file where your split occurs.

Excluding that one issue, this part couldn’t be easier. Just select a section of audio, go to the File menu, and choose Export Selection again. This time, choose MP3 in the “Save as type” drop-down list and pick your desired quality using the Options button. You can fill in the tags in the following screen, then hit OK to export your MP3. Repeat for each song/section/whatever in your source audio.

That’s it! Now you can listen to all your old cassette favorites with the convenience of portable digital formats, and less tape hiss.

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