The guiding principle at the Macaulay Library is to create an archival recording that is an accurate copy of an original field recording. This means doing a minimal amount of editing to sound files. Here are some tips from the Macaulay Library on how you should (and shouldn't) prepare your sound recordings before uploading them to an eBird checklist.
These general guidelines are applicable in any sound editing program, but we also have created detailed “How To” documents illustrating these guidelines (see bottom of this page), for two popular editing programs: Adobe Audition and Audacity (available for free at http://audacityteam.org). In addition, we've created a series of instructional videos demonstrating how to use Adobe Audition for bird sound editing.
- Create and submit .WAV Files
- If you created .WAV files in the field, upload .WAV files to your eBird checklist.
- Trim Recordings
- Trim the ends of the sound file so that the recording has a clean start and end.
- Include up to 3 seconds of clean audio at the start and end of the recording if possible.
- Normalize Bird Sounds and Voice Announcements
- Adjust the level of each sound file so that the loudest bird sound reaches -3 dB.
- Adjust the level of voice announcements to a peak of -10 dB.
- Pay Attention to Individuals and Group Files Accordingly
- If you record two or more sound files of the same individual bird, edit each sound file separately and then put the files together in a new sound file; upload this new file to your eBird checklist.
- If you record one sound file from one individual, and then record a second sound file from a different individual of the same species, you should submit each of those sound files separately, and not group them together.
- Avoid Filters and Cosmetic Editing
- After trimming the ends of a sound file, do not edit to minimize insect noise, remove background species, etc.
- Filter only when necessary—if a low frequency sound is masking your target species, apply a gentle low-cut/high-pass filter at the minimum frequency possible (250 Hz or less).
- Include Voice Announcements
- Make voice announcements in the field with species, date, time, and location information, as well as any other important notes about behavior, habitat, recording equipment, and weather.
- Append these announcements to the associated bird recordings
Save Copies of Your Original Sound Files
Many sound editing programs are “destructive,” meaning that if you edit a sound file in the program, your original sound file is permanently changed. Therefore, it is extremely important to keep copies of your original field recordings that are not modified in any editing program. The Macaulay Library recommends keeping two copies of your original sound files—one on your computer, and a second on an external hard drive—and using a third copy of the files for editing purposes.
Ride the .WAV
The eBird upload tool can handle large audio files—up to 250 MB in size!—so if your original field recordings are .WAV sound files, be sure to upload .WAV files (not compressed .mp3 files) to your eBird checklist.
Trim The Ends
The beginning of a sound file is often the messiest part of the recording. Recordists sometimes make noise as they start a recording and get situated, and then there can be a significant amount of waiting time before a bird actually sings. When reviewing your sound file, create a break at the beginning so that there are a few seconds of “clean audio” followed by your target sound as the first prominent audible sound. If possible, include up to 3 seconds of “clean audio” before this first sound, but if there is handling noise or a loud background species during these 3 seconds, create an appropriate break that is only 1-2 seconds before the first target sound. At the end of the recording, after the last target sound, apply the same approach of including up to 3 seconds of clean audio before creating an end break.
Don't Make It Pretty
Sound editing software can be a very powerful tool, allowing you to "erase" background birds, loud insects, raindrops, stomach growls, etc. While it can be tempting to remove these types of sounds from your recordings, we encourage you to give us recordings that include what you heard and recorded in the field, even if it’s not all pretty.
Keep It Continuous
If you have made a long, continuous recording of a bird that vocalizes infrequently (such as an owl), be sure to keep the entire recording. There is valuable information in the silence between songs—information that is lost if a continuous recording is chopped up into many short segments.
Let Us Hear You
We encourage recordists to make voice announcements in the field and append these announcements to their bird recordings. Making a voice announcement in the field is a great way to capture important information about behavior, habitat, weather, and recording equipment, as well as core data like date, time, and location. If you make a bird recording in one sound file, and then make a voice announcement in another sound file, merge the two together in a single file before uploading to eBird. (In other words, please don’t upload a sound file that only contains a voice announcement.)
Boost The Bird Sound
Even when you're close to a bird and have made a great recording, chances are that the bird sound could still benefit from being boosted a few decibels. At the Macaulay Library, we adjust the level of each recording so that the level of the peak bird sound reaches -3 dB. This makes it easier to hear the target sound in a recording, and creates a consistent listening experience between recordings made at different times and places by many different recordists. Human voice announcements, on the other hand, tend to be quite loud compared to bird song, so we keep the peak level for those announcements at -10 dB.
Group Recordings of the Same Bird Together
On those rare occasions when a bird is cooperative and you're able to make multiple recordings of the same individual bird, treat each sound file as described above, and then group the files together in a single file with one second of silence between each recording. The new file is the one that should be uploaded to eBird. This grouping of files should be done only when all of the files are from the same individual. Alternatively, if you record one sound file from one individual, and then record a second sound file from a different individual of the same species, you should submit each of those sound files separately, and not group them together.
Filter Sparingly and Gently
In certain circumstances, the Macaulay Library will apply a filter to a recording during the archival process, but this is done rarely, and only with a gentle filter (250 Hz or less). If the target bird is the loudest sound in a recording, there is no need to filter the recording at all. If there is a strong low frequency sound in a recording (such as wind or distant road noise) that is masking the target sound, then it is appropriate to apply a low-cut/high-pass filter that is just high enough to reduce the low frequency sound.