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Deleting Recordings: While the playback is running or when it is complete, you can press the trash key to delete. Press the Record button for confirmation of the deletion. A message ‘Done’ should appear once the deletion is complete.
Extracting and Splitting
- First install Audacity and follow the instructions for downloading. You will need the LAME mp3 encoder to use audacity. You can download it for free by searching for lame_enc.dll.
- Configure the MP3 encoding settings in Audacity (Edit -> Preferences -> File Formats -> Bit Rate). For speech, 64kbit mono encoding should be adequate. If the audio contains other noises or music, 96kbit mono could be considered. For very high quality applications (at a minimum, CommCare user will be using headphones) use 128kbit stereo. 64kbit mono requires ~7KB per second of audio. We use variable bit-rate encoding (better quality for a given file size).
- Extract the recordings from the recording device.
Convert the recordings into .wav format if they are not already converted (most mp3 players have an option to create .wav files).
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- Open the recording file in 'audacity' (music editing program)
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You should be able to see the numbers and phrases clearly. For each phrase, select the portion you want to extract as the audio clip (with a slight pause both before and after the speaking). Skip attempts that are not usable. Among all the takes for each phrase, choose the best one and discard the rest.
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- If this file has multiple speech recordings(as shown in the pic below) in the same file then select the portion of audio (highlighted) you wish to process. Copy and Paste in a "new project". If not continue to work in the same project.
- Listen to the selected piece once.If there is a lot of background noise which could be the case with recordings done in the field,its best to remove them to ensure we have good quality recordings. Here is detailed video( Watch from 6:54 to 10.48) on how to do the same. NOTE: This may not be the best way to do it and it can be time consuming, so the better thing to do is, obviously, be careful while recording to ensure there are no background noises.
- Once you have finished removing background noise, you can check for any blank noises/unneccesary pauses in the audio piece and delete them. The objective is to keep the audio recording crisp and precise. So, to remove the blank noises/unneccesary pauses, drag and select just that portion of the file and press delete.
The next step is to amplify the volume of the audio file. The audio files when played by the chw's on their phones needs to be relatively loud since field environment is prone to noise. Select the entire audio file (ctrl+a).Go to effects and choose amplify
- In the pop-up box, input 10 in the "amplification" field and below, check the box "allow clipping" (see pic below) and click ok
You will notice the audio file will have vertically stretched out bars indicating that the volume has been amplified.
Now, to save this audio file as .mp3, click on file, export and save the file with the desired file name.
Post-processing
This step makes all the recordings approximately the same volume. First download and install MP3Gain.
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