Using Audacity Spectrograms to Review Audio - A Cheat Sheet

This is a quick tutorial and list of actions that will get the first time user up and running with Audacity, for the purpose of reviewing their audio files visually, with spectrograms. This assumes you are already familiar with how to open an audio file in Audacity.

-Start Audacity and maximize the application's window to fill your whole screen
-The first time you use this tutorial you'll want to type "Ctrl-P" to open the Audacity Preferences window
-In the Audacity Preferences window select "Spectrograms" to bring up the associated options
-In the spectrogram options set window size to "4096 - most narrowband" (later versions of Audacity allow for much higher settings, but greater than 8192 may be of little use for this purpose)
-Set Maximum Frequency to 1200, and click the box to "Show the spectrogram using grayscale colors" (Gray scale is easier to work with until you're more familiar with spectrograms)
-Select OK to save your settings

See the image below for added examples of these settings...

-Now select File>Open and choose an audio file to load into Audacity
-Grab the bottom edge of the sound track when it opens and drag it down to fill in the empty space in the main application window (or you can hold down the Ctrl and Shift keys simultaneously and hit the "F" key to achieve the same effect)

-At the top left of the sound track, the file's name will appear with a small down arrow to the right of the name
-Select that arrow and a drop down menu provides options to apply to the track, select "Spectrum" or "Spectrogram" in newer versions of Audacity

-In the resulting spectrogram view, use your mouse to select a segment of audio to examine.
-Start with 10-20 seconds until you've become comfortable with the types of patterns to look for.
-Select the button in the top right of the main toolbar to "Fit Selection", this will cause the view to zoom in to the audio you've selected with your mouse

-Use the scroll bar at the bottom of the audio file window to jump the audio right one segment of time (based on the duration you selected above).

-Scroll through the audio a bit at a time and watch for dark spots in the spectrogram which indicate an audible sound has been recorded
-When you spot something worth listening to, click your mouse just to the left of the dark spot and then hit the space bar on your keyboard to begin playback
-Listen to the sound, and after you've heard it, hit the space bar again to stop playback

Here's an example of how coyote howls appear in an audacity spectrogram set up as discussed above

-Use this method to scroll, view, and selectively play back audio until you've completed the entire file
-If you find something worth isolating, use your mouse to select that section of audio and then the menu options File>Export Selecttion to save that segment to a new file.
-One of the biggest advantages spectrogram review has over the normal "waveform" review method (where you watch for big spikes in the audio file's waveform view), is how spectrograms show you howls that are otherwise hidden in the waveform. As an example compare the spectrogram view of the coyote howls above, to the waveform view of the same coyote howls, below. In waveform they are complete invisible and would go unheard if you weren't lucky enough to play back that segment of audio.

 
-After you've become comfortable scrolling through spectrograms, recognizing interesting patterns (sounds), and playing them back, you should try widening the view on your screen
-A three minute segment (vice the 20 seconds described above), gives good visual detail when in full screen mode, and allows you to review hours of audio very quickly (as compared to listening to the entire file)
-This is what makes it possible to record 9 hours of audio every night, and then quickly review it in under thirty minutes at some future date (more recording means more chances of catching a sasquatch vocal)

Other special notes:
-Most good sasquatch vocals occur between 500 and 800 Hertz, but can appear above or below that (although rarely seen above 1200 Hertz)
-Howls will look like long flat or wavering horizontal lines (-----), whoops look like the forward slash on your keyboard (/), woodknocks look like tall vertical lines (|)
-Dogs most often appear in the 350-500 Hertz range, and owls are all over the place
-In my experience, most good audio occurs between 10 p.m. and 4 a.m.

Triple Moan Howl from Morton, Washington

Kirk Brandenburg has been on a tear lately. Earlier this year he captured a great piece of thermal footage potentially showing a New Mexico sasquatch monitoring his camp one night. But before that, in August of 2010, Kirk was camping with friends in Morton, Washington, when he heard vocals starting up in the distance. Kirk had the presence of mind to grab his audio recorder, turn it on, and listen quietly. For his efforts, Kirk captured one of the best series of moan howls to be recorded recently. It makes for a nice spectrogram, and after cleaning up, has a bonus whoop or two at the end.

After you've enjoyed this clip, be sure to check out Kirk's thermal footage at:
http://www.youtube.com/user/studysasquatch

Best of the Sasquatch Bioacoustic's Video-Spectrograms

This list captures the "best-of" the video spectrograms published here at Sasquatch Bioacoustic and serves as an easy reference list for the interested listener.

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The Ohio Howl - The first recording of a "Moan Howl" known to have been captured, in 1994, by Matt Moneymaker of the BFRO. This comes from Columbiana County Ohio, near Wellsville on the Ohio River. The original clip may be found at: http://www.bfro.net/avevid/SierraSounds/911.asp#howls

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The Mississippi Howl - On December 19th, 2004 in Forrest County Mississippi, John Callender recorded a sequence of long moan howls, very similar to the Ohio Moan Howl of 1994. However, careful post-processing of John's recording reveals more than meets the ear, including a whoop and what may be the first known recorded instance of a "falsetto shriek" and a "yahoo" vocal. Both of these vocal types have been captured repeatedly in the years since.

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The Florida Howl - The first moaning howl recording captured in Florida, by Dan McGee, during a 2006 BFRO expedition to Lake County

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The Kentucky Vocalizations - On April 10, 2010, Billy Arndell and members of the Scottsville Ghost Hunters were visiting an abandoned house in a large wooded tract. Billy placed an audio recorder inside the house, near a broken out window, and captured this series of vocalizations while he and his friends talked outside.

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Recorded by Kirk Brandenburg at 5:56 pm, August 20, 2010, near Morton, Washington. He and his group had just arrived and were in the process of setting up their camp when these vocals began. Kirk had the presence of mind to quickly start his audio recorder and captured this great vocal sequence. The moan howls in this clip are highly consistent with moan howls captured in Ohio, Mississippi, Florida and Georgia. This clip begins with an indistinct vocalization, possibly from a different sasquatch, and ends with two whoops.

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Piney Woods Up Vocals - Captured on August 31, 2011 at 10:50 p.m. in a research area in Pendleton County, West Virginia. These ascending vocals follow shortly after two faint whoops and resemble similar vocals captured in Brunswick County, VA. The second half of this clip includes spectral amplification to bring out the faint initial whoops, and other details of the ensuing vocals. Compare the two whoops in this clip to the series of whoops captured in Decatur County, GA in March 2011, in this clip: http://www.youtube.com/watch?NR=1&v=u0wuRSFena4

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Decatur Moan Howl - While vacationing in south Georgia I decided to visit a remote forested area to listen to night sounds and make wildlife recordings. After sun set there were a lot of owls calling and several alligators growling from the nearby river. At one point I heard three wood knocks come from the forest, and as I continued to listen I heard two distant whoops. I left my recorder out over night and at about 12:05 a.m. on the 12th of March, the recorder captured this distant moan howl. If was quickly followed up with a bonus ascending howl, and then ended with three wood knocks.

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