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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The Kentucky Vocalizations

This clip, "The Kentucky Vocalizations", is one of the more important recordings to surface recently in the effort to study sasquatch vocal types and communication patterns. This is not due to any particular clarity in the clip, in fact it's a great example of what not to do while making a recording. But the vocalizations captured here cover a range of suspected sasquatch utterances that have only appeared singly or in pairs in other recordings. In a sense, it becomes something of a touchstone for a broader range of sasquatch calls. It does so by establishing relationships between heretofore unrelated vocals, and in this case, most apparently spoken by the same vocalizer.

And it is the relationships between vocals that allows us to extend the potential content of the sasquatch vocabulary. It begins with a single instance of one form of communication captured in association with another, which creates a potential connection between the two (for instance, the moaning howls and possible response howl in the "Ohio Howl"). And then, with time and additional data, we find evidence to support or refute that hypothetical association. This activity of mapping and substantiating vocal relationships is a key technique enabling this type of study.

The Kentucky Vocalizations were inadvertently captured by the late Billy Arndell and a group of paranormal investigators known as the Scottsville Ghost Hunters. During the evening of April 10, 2010, the group visited an abandoned house in a large wooded tract in Allen County, Kentucky. Billy placed his audio recorder inside the house, near a broken-out window, and stepped back outside to converse with his friends. While they talked, the recorder captured an impressive series of vocalizations. Unfortunately their conversation steps on much of the recording, but careful filtering and amplification has salvaged many interesting features, including:

Whoop modified with trailing utterances - At the two second mark of the spectrogram playback, and again at the 15 second mark, a subdued "whoop" vocal is heard. These two whoops are unique with regard to the vocal notes that follow immediately after them. These trailing notes are, to date, not seen in any other potential sasquatch recording. And as a possible first occurrence, this recording takes on added value. This type of call will be listened for in future recordings of possible sasquatch vocalizations.

Moaning howl - At 20 through 29 seconds of the audio playback, a loud vocalizer (louder than the initial two whoops) emits two long moaning howls. These are very similar in construct to the moaning howls heard in the Ohio Howl (1994), Mississippi Howl (2004) and the Florida Howl (2006).

Integrated wood knock - Not a vocalization, but wood knocks are a frequently described signal in suspected sasquatch communications. From 21 to 23 seconds, during the beginning of the first moaning howl, three heavy wood knocks are made. They are difficult to hear in the original audio recording, but show up faintly in the spectrogram as light vertical bars intersecting the howl. With amplification, they are easier to hear in the filtered audio playback. Wood knocks are often integrated into sasquatch vocalizations and can be seen in both the Mississippi and Florida Howl recordings.

Woot vocal - The name of this vocal is an onomatopoeia, or a name that sounds like the thing it describes. This vocal type is not commonly heard, but it has been captured in other audio recordings. In this clip, three possible woots are uttered in rapid succession, at the 31 second mark in the spectrogram playback. They could be mistaken for wood knocks, but  the lack of a broadband, woody note suggests these are indeed vocals.

Yell - This vocal type is often long in duration, similar to a moan howl, but it is executed at a higher frequency. The resulting change in tone and timber creates a vocal that sounds very much like a human male yelling in the distance. Heard on its own, it would be completely indistinguishable from a human calling out. But in many instances, the yell vocal is captured in association with other suspected sasquatch vocals. In this recording, an ascending yell vocal begins just before the 32 second mark and climbs steadily in pitch for 3 seconds. Then it breaks to a higher pitched tone, briefly, before breaking again and descending in pitch to the call's conclusion. There are two additional short segments of "yell" in this clip, at the 38 and 42 second marks. But these are integrated into a unique call, discussed below in "pitch changes".

Whistle - From 37 to 38 seconds in the clip, four short notes are emitted, sounding very much like whistles. They could in fact be vocals, but the airy note they contain suggests a whistle. Other examples of this vocal type exist, but more need to be captured before a conclusion might be reached. The first three whistle notes climb rapidly in pitch, and the fourth drops to a lower pitch, below the third. Of interest is the fact that the fourth whistle is emitted during a second, shorter yell vocal from the vocalizer. This suggests a second sasquatch could be uttering the whistles in response.

Falsetto Shriek - This vocal type was probably first captured in the 2004 Mississippi howl recording. It rounds out the sasquatch vocal range, with moan howls at the low end, yell vocals mid range, and the falsetto shriek at the high end, or in the falsetto register (if compared to a human vocal range). This clip contains two falsetto shrieks, the first at the 39 second mark, and the next at the 45 second mark. As the second shriek plays out it drops out and in again at 52 and 55 seconds.

Pitch Changes - The vocals in this recording include abrupt breaks in pitch, to both higher and lower notes. These pitch changes have been observed in other sasquatch vocals with enough regularity to become something of an identifier in themselves. A future blog post will deal more specifically with pitch changes and what's been observed to date. But for this clip the reader should note the minor pitch changes at 35 and 36 seconds, and the significant pitch changes at 39, 42 and 45 seconds. These latter mark the transition from a yell vocal into and out of a falsetto shriek, as described above.

To our great fortune, the Scottsville Ghost Hunters knew they had something interesting with this clip, so they contacted Charlie Raymond of the Kentucky Bigfoot Research Group (www.kentuckybigfoot.com). Charlie and I know each other from a chance meeting during the 2010 BFRO expedition to Tennessee where he learned of my interest in the study of sasquatch vocalizations. Thankfully Charlie contacted me with this clip for closer scrutiny, and I am grateful to Billy Arndell and the Scottsville Ghost Hunters for sharing this great audio evidence with the sasquatch research community.

Scrutinizing the Florida Howl

It's time to look at another venerable vocal capture possibly attributed to sasquatch. This one is known as the Florida Howl, and it was recorded in Lake County, Florida, by Dan McGee, as he attended a BFRO expedition in January, 2006. You can read the report and see photos from that expedition on the BFRO website.

 
After some noise filtering and amplification three things emerge to recommend this as a sasquatch howl.

First, the familiar arched shape of a "moaning" howl, seen in both the Ohio and Mississippi video spectrograms.

Second, it shows an attenuated fundamental with strongest resonance in the F1 harmonic.

And third (and more importantly), there appear to be three deep wood knocks integrated into the howl, one at the beginning, and two at the end.

Integrated wood knocks are a key feature to look for in sasquatch vocals, and this capture has them. So +1 for the Florida Howl being the real deal.

Examining the 2004 Mississippi Howl

On December 19, 2004, John Callender was in Forrest County, Mississippi investigating a report recently submitted to the BFRO. It was just after 11 p.m. and he used his video camera to capture nearly forty seconds of distinct moaning howls. The resulting audio file has been available through BFRO's website, www.bfro.net, for many years.

Upon cursory examination in a spectrogram, the characteristic arch-shaped form of a moan howl is readily recognized. It is very similar to what is seen in the Ohio Howl, recorded in Columbiana County, OH, in 1994. There are also attenuated fundamentals in each howl, a characteristic seen in the Ohio howl, and an expected attribute when examining this type of sasquatch vocal.

The recording itself is a victim of the electronics used to record it. There is a high pitched hum through out the clip that creates interference across a broad range of frequencies. Fortunately, the most annoying pitch is easily knocked out with filtering. And after amplification, the result shows a number of new features that weren't readily recognized in the original clip.

Highlights of the Mississippi Howl 2004 include what may be the first known recording of both a "falsetto shriek" and a "yahoo vocal". (There could be earlier recordings that include these features, but to date they have not come to my attention.) In addition to these, there is a clear whoop vocal and several percussive sounds that could be wood knocks.

The term falsetto shriek is a concatenation of two attributes recognized separately. Over many months of studying this vocal type in a number of similar recordings, I could find no better name for it than a "shriek" based purely upon the vocal quality, timbre and tone, that it displays. But during the Pennsylvania 2011 BFRO expedition, Todd Prescott remarked that the vocal was in a falsetto pitch. He was right of course and I validated his comment against a number of other shrieks. The term falsetto shriek is now used to portray a truer verbal description and mental image of this vocal type.

Yahoo is an onomatopoeia, or a name that sounds like the vocal to which it applies. This vocal originates much lower in the sasquatch vocal register than the falsetto shriek and is no higher pitched than the majority of howls and whoops attributed to sasquatch vocaliations. It is also relatively unknown, somewhat rare, and possibly captured no more than a dozen times. After hearing several instances of this understated vocal, often in response to much louder calls, the name yahoo came easily to hand. The vocal itself sounds like a person yelling out YAHOO in the distance. The first syllable is always ascending, and the second syllable is always descending. But there can be variations on the vocal. At times it sounds like WAHOO, with a distinct /w/ sound in the beginning. The yahoo vocal in the video spectrogram above is an instance of the wahoo variation.

This Mississippi Howl spectrogram attempts to lead the viewer's eye to the specific signals that represent the falsetto shriek, the yahoo, and other interesting features. But there is just too much going on in the filtered clip to fully annotate all the elements that have been uncovered. Instead, consider this spectrogram an introduction to an initial assessment of the recording, and in a future post I will dive deeper into falsetto shrieks and other things, like resonance shifting across harmonics.

A Closer Look at the Ohio Howl

Near Wellsville Ohio in 1994, Matt Moneymaker recorded a loud moaning sound that would go on to become known as the Ohio Howl. Since its capture, that sound has become associated with the voice of a sasquatch vocalizing somewhere in the hills along the Ohio river. Indeed, in the years to follow,  this howl would be heard and recorded in a variety of locations across North America. It has now become so well known that the Moan Howl forms the basis for many attempts by researchers to lure sasquatch into vocalizing for the recorder.

Such an important piece of evidence for the existence of bigfoot naturally bears closer scrutiny for the purpose of A) identifying unique characteristics, B) differentiating it from known vocalizers, and C) looking for similar patterns in other potential sasquatch vocals. When similar patterns are found, an association is established, and unique characteristics from the newer recordings may be added to the body of knowledge regarding sasquatch vocalizations.

For those interested in how sasquatch communicate with others of their kind, this type of investigation can be deeply intriguing. And in my efforts to examine this matter I've found a large number of researchers with a wide collection of audio captures that fall into the emerging profile of the sasquatch voice. They've been very generous with their ideas and their recordings, and networking with them has allowed me to put many theories together, validate or invalidate several ideas, and make some minor discoveries of my own along the way.

In the weeks and months to come I will be releasing a series of video-spectrograms, similar to the one above. In these spectrograms I will highlight characteristics of these calls and demonstrate their relationship to other sasquatch vocals. With time a profile should emerge which builds a picture of both common sasquatch calls, and some rare and strange sasquatch vocals as well.

In the mean time, let's begin with the Ohio Howl. I'd like to point out three features in this recording that are worth becoming familiar with.

First, the attenuated fundamental. This was first brought to my attention by Bob Densford from Texas. If you watch the spectrogram as it plays, you'll notice a series of stacked lines (all gently curving arches) coinciding with the sound of the howl. The lowest line is called the fundamental frequency (F0), the next line up is a harmonic of that frequency (F1 or 2x the fundamental), and the next up is another harmonic (F2 or 3x the fundamental). Upon closer examination, you will see that F0 is visually dimmer than F1. It is diminished in power, or attenuated. F1 is actually much brighter than F0, stronger than any of the other harmonics, and is where the vocal "resonates" the strongest. This is the note that you hear most clearly with your ears (although the fundamental and other harmonics are contributing to the richness of the sound). Attenuated fundamentals are not unique to the sasquatch, but they do appear in many of the recordings with the best potential for being a sasquatch. They are one of the hallmarks that I watch for when trying to rule a recording in or out.

Second, just after the 7 second mark in the howl recording (14 seconds on the video) there is a softer, flat howl, that sounds like a low "wooooo". This is not readily noticed in the original audio file, but it stands out clearly after cleaning up the dog barks that are stepping on it. More data is needed to back up this theory, but I believe this might be a response to the loud vocalizer, coming from a second sasquatch. I base that idea upon recognition of very similar, low flat howls, in a number of similar recordings. I've even heard this low howl twice while in the woods investigating. Over the weeks and months ahead I will single out this vocal in other video-spectrograms.

Third and finally, I would call your attention to the shape of the howl in the spectrogram. Moan howls have a characteristically long, gentle arch shape to them. Few other vocalizers routinely produce this shape. Coyotes are often more erratic and shorter. Wolves are often very flat and long. Cows can come close, they are deeper and shorter. This type of howl could be produced by man or canine, but the unique form is something to watch for when examining an audio clip. Combine that with other attributes (like frequency range) and the profile of the sasquatch moan howl becomes much easier to recognize.