Remove sensitive or unwanted sections of a stored audio file (LENA SP)
This article for LENA SP explains how to use LENA exports and third-party software to replace a section of the stored WAV file with silence.
A few important notes:
- These instructions affect the stored WAV file only. You cannot remove audio during recorder transfer, edit the UPL before processing, or edit the UPL and reprocess it.
- Replacing sections with silence, rather than deleting, preserves the temporal relationship between elapsed time in the WAV file and elapsed time in the LENA SP data exports (CSV, ITS). This means you can still identify an area of interest in the data and jump to it in the WAV, and vice versa - which would not be possible if portions of audio were deleted.
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Editing the WAV file in this way has no impact on the processed results (counts, percentiles, AVA and VP scores).
- If you wish to exclude words, vocalizations, and turns from the same section, you will need to use exported ITS file data and calculate count totals manually, excluding the portion corresponding to the cut audio.
- There isn't a way to exclude these sections from AVA and VP calculations, or from the totals used to produce percentiles on the reports.
Note: This article pertains to LENA SP only, and not to other products where the audio is automatically destroyed after processing.
1. Gather the necessary information and tools.
You will need:
- the WAV file you need to edit
- the corresponding 5-minute recording export, OR the corresponding ITS file export + ADEX to pull data from the ITS (see options in Step 3)
- a spreadsheet program, such as Microsoft Excel
- third-party audio editing software, such as Audacity
You can verify the file name for the recording in the ITS File column of the child's Recordings screen, or in the ITS_File_Name column of the Recordings export.
2. Make a temporary backup of the .wav file.
This is your backup in case you make an error in the audio editing process.
3. Identify the starting and ending elapsed times for the portion you're replacing.
There are two options - click for details.
Use the 5-minute recording export of this recording to find the elapsed time for the beginning and end of the closest 5-minute sections of the WAV file.
You'll use the Duration column to calculate elapsed time for each 5-minute chunk, and then you'll use the StartTime and EndTime columns to navigate. You can add a single column to show the starting point for each row, or you can show both the start and end points. The steps below show both start and end.
- Make 2 new columns called StartElapsed and EndElapsed.
- Set the StartElapsed value for the first row as 0.
- This is the beginning of the recording, so the 5-minute section starts at 0 seconds into the recording.
- Calculate the EndElapsed value for row 1.
- The elapsed time for the end of the row is StartElapsed value + Duration for the row.
- Set the StartElapsed value for the 2nd row as the EndElapsed time from the previous row.
- Carry the formulas down to the bottom of the sheet. (In the example the columns have also been formatted to show they are calculations.)
- Match up the clock times for the section you want to replace with the corresponding elapsed times.
In this example, we want to replace the portion of the recording between 8:00 and 8:20, so when working with the .wav, we'll find the portion of the audio that starts 2,666 seconds into the recording and ends at 3,866 seconds.
This is the best option if:
- your project does not already work with the ITS file and/or ADEX, and
- it is acceptable to lose up to 5 minutes of audio on either side of the audio you wish to remove
This method works whether your WAV file is continuous or contains many separate recordings that were processed as a single file (as can happen when the recording is briefly paused and then restarted).
To find more precise start and end times for the section audio to be replaced, use ADEX and Excel to correlate clock time and elapsed time in the ITS file.
This is the best option if:
- you already work with ITS files
- you do close transcriptional analyses that factor in LENA speaker segment boundaries, and/or
- you require extreme precision in what is removed and what remains.
4. Use other software to edit the .wav file.
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Replace the corresponding elapsed time range(s) with silence. Do not remove the sections.
- Replacing preserves the relationship between clock time and elapsed time throughout the file for later navigation and correlation with LENA export data...and for replacing additional sections!
- In Audacity, the method is to select your precise elapsed time range using fields at the bottom of the screen, and then choose Edit>Remove Special>Silence Audio.
5. Overwrite the original .wav file.
6. Delete the backup .wav you made in a previous step.
If your program has established any automatic backups of LENA data, delete the WAV file there as well.