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.

Ascending Vocals from Pendleton County, WV

On August 13, 2011 I dropped off a new "long duration audio recorder" in my  Pendleton County research area. This was to be the recorder's first field trial and I had high hopes that it would perform well. I also hoped the vocalizers I'd recorded in the area previously would be frequently active and vocal.

I chose to place the recorder in a dense patch of mountain laurel, close to a place I've nick named the Piney Woods. It was at this location that I was growled at in 2010, and where I recorded loud vocalizations from during the Spring of that year. The mountain laurel was thick enough to hide the recorder from anyone who might happen by (although not a likely event, I have lost recorders that weren't well hidden).

The recorder captured 9 hours of audio each night, from 9 p.m. till 6 a.m., for 32 nights in a row. The 16 GB memory card finally reached capacity and recording ceased. Happily there was plenty of battery power remaining, so longer deployments are possible in the future with a larger memory card.

I picked up the recorder on the evening of October 7th, as I was driving through Pendleton County on my way to another destination. And since then have used Audacity's spectrographic tool to review the audio visually and watch for the tell-tale signature of potential sasquatch vocals. Unluckily, the recorder picked up a good deal of human traffic in the area while it operated. And that may have put down some of the activity in the area. But to be fair, the summer months have never been terribly productive in that location.

However, on the 31st of August, and 10:50 p.m., the recorder did capture a series of vocals that begin with two faint whoops, and then evolve into four ascending vocals, each louder than the one before. These "ascending" vocals have a strange, siren-like quality to them.

I've put together this short video of the spectrographic playback of these vocals. It plays through twice. The first run is very close to what the original recording sounds like, with only mild filtering and amplification applied. The initial whoops are so faint that they can't be heard without headphones. The second play through in the video includes an enhanced version of the clip where a spectral editor has been applied to enhance the amplitude of the vocals themselves. The howls are louder, and the initial whoops are clearly heard.

Building a Long Duration Recorder

I've long sought to piece together an audio recorder capable of running unattended,for weeks on end, in remote forest locations. While it has been possible to put such a rig together for some time, it was always a costly affair. It wasn't until recently that all the right products became available, off the shelf, and for a price that wouldn't break the bank. I recently assembled a field recorder for under $200 that operated for 43 days in the field, recording 290 hours of audio (10 hours per day for 29 days, until the memory was filled). For the record, here's how I did it...

Key to the system is an affordable, effective, and configurable audio recorder that can be powered from an external power source. I found just such a device in the TASCAM DR-03 for about $79. http://tascam.com/product/dr-03/

The DR-03 includes firm-ware that allows it to be configured to start recording at one time, and stop recording at another time (impossible to find in other affordable recorders, but maybe not so in the future). It also accepts micro SDHC memory cards where it stores the recorded audio, so increasing the amount of storage is a factor of how much you want to spend. Finally, the recorder comes with a USB port which can be used to power it, from an external source (AC or DC).

So with the recorder in hand, I needed a good battery to power it from. I found a great solution at Walmart in a deep-cycle 12 volt marine battery with 105 amp-hours of power (more amp-hours means more recording time in the field). It was nicely priced at about $65. Also in the automotive section at Walmart I found a battery clip extension that clips to the battery's terminals and provides a cigarette lighter-type power socket ($6)
http://www.google.com/search?q=battery+clip+extension

In the same area I looked for and found a 12 volt dc to usb adapter ($7).
http://www.google.com/search?q=12+volt+dc+to+usb+adapter

And finally, in the camping section, I found a tough plastic storage bin to house everything and protect it all from the elements ($20).

The last thing I purchased was a 16GB mini memory card for $35 from Microcenter. All together I have $187 in the materials for this device (I got the recorder on sale for $49).

Putting the thing together was straight forward. Not necessary, but highly recommended, I added a pair of external mics that I already owned ($75 from Giant Squid Audio Labs - http://www.giant-squid-audio-lab.com/gs/gs-podcast_stereo.html ).

I started by installing the 16GB memory card into the DR-03 recorder. I then powered up and configured the recorders timer function to begin recording at 8 p.m. each evening, and to cease recording at 6 a.m. each morning.

Next I charged up the 12 volt battery to ensure it was topped off before I put it out in the field. I placed the battery in the storage bin and added padding around it so it would not shift while in transit. I drilled a couple of small holes under the handles of the bin where the microphones could poke out, but receive protection from rainfall by the handles above them.

I connected the audio recorder to the DC-USB adapter with the USB cable that came with the recorder. I then plugged the DC-USB adapter into the DC socket on the 12 volt battery clip extension. I connected the battery clips to the terminals on the 12 volt battery, and voila, the recorder powered up.

I plugged my external stereo mics into the audio recorder and then pushed the mics out through the tightly fitted holes I drilled under the bin's handles. I used small strips of duct tape to secure all of the connections and equipment in place. Mics were taped to the bin. Plugs were taped into sockets. Even the clips were taped to the battery. I didn't want anything to shake loose easily, should something upset the box while it was in the field (short of turning the whole thing upside down).

Finally I placed the recorder inside a gallon-sized zip lock bag to protect it from direct precipitation. I did the same with the USB-DC adapter for good measure. And then I taped both securely to the inside of the bin's hinged lid. I closed the bin, which is equipped with a latch for a padlock, and used stout wire to secure the lid closed.

And that's exactly how it sat, deployed to the field for 43 days, recording 10 hours every night (for 29 nights).

Since that deployment I've learned a few things that will help me improve the system, or build a second one for less cost.

First, the recorder does not need to stay powered on, as I had left it. It can be turned off and the automatic record function will power up the recorder at the proper time and begin recording. It will also power the recorder down after recording is complete. This feature will save a lot of power and allow me to get by with a much smaller battery and storage bin (Walmart has a 12 volt lawn mower battery for $20 that should power the recorder for a month).

Second, maxing out the mic sensitivity might cause some recording problems. In my first field test there are segments, especially during noisy parts of the recording, where interference obscures the recording. This may be a result of turning mic sensitivity up to max.

I'll build a second version of this field recorder and test the onboard mics for their sensitivity. If the prove good enough then I may leave the external mics out of the build and just go with what the recorder has built in. It will present a challenge when trying expose the mics from the case to gather sound, but still protect the recorder from precipitation. But I think it can be managed. Either way, the next version of the recorder should be smaller, lighter, and easier to pack out into the field.

Looking at New Areas in Virginia

Back on June 11th I decided to check out some new areas in Virginia (not West Viriginia) that may support sasquatch. While camping in these new areas I hiked extensively and put out multiple audio recorders to capture any vocalizations that might occur.

On the first morning, a very rainy night in the national forest, two loud wood knocks occurred just outside camp. They were loud enough to wake one of the folks in camp (I slept right through them):

http://sites.google.com/site/mongahela/myrecordings2011/110610_01-07-TwoBigKnocks.mp3

Much later on the 11th, just before midnight, a recorder I placed in a remote river bottom picked up a series of strange howls. They're very dissimilar to any coyote or dog howls I've ever recorded, but unlike many of the potential sasquatch howls I've studied. So in their own right their worth keeping track of, in case more such howls should be captured in the future:

http://sites.google.com/site/mongahela/myrecordings2011/WS500020-02-StrangeHowls-HPLPHRLPx3.mp3

Then finally, at about 5:30 a.m. on the 12th, as the sun was coming up a single whoop was captured by my camp recorder. I was still sleeping when this occurred, but it further supports my belief that one or more sasquatch are living in the region:

http://sites.google.com/site/mongahela/myrecordings2011/110611_02-08-MorningWhoop-SpectralEdit1-AMHPLPHR.mp3

The Rest of the Story

I need to complete the audio picture for the night I left recorders out in my research area, last March 25th. The first was shared in my March 31st post, but it's worth reposting to help show the context of what occurred over the course of the evening.

Just at sun down on March 25th I hiked in to a remote location in my research area, accompanied by a friend and his son. We put out an audio recorder and then did about a half dozen whoop-knocks. It grew very dark and we walked out without head lights. There was just enough light to make out the path back to my truck.

Later I reviewed the audio and found three interesting clips. The first occurs about 30 minutes after we leave the area, at 9:09 p.m. It sounds as though a bipedal walker approaches from the north (left mic channel). To the north of this location is a deep and isolated valley that is largely trackless. The walker is not alone, at times you can hear a second visitor moving about in the back ground. This short clip is from the first 4 minutes or so of the visit. The visitors stay within ear shot of the mic for about 20 minutes, before eventually moving away:

http://sites.google.com/site/mongahela/myrecordings2011/WS500017-01-BipedalSteps-HP.mp3


Next, just over an hour later, the recorder picked up a vocalization that I've captured a few times in this area. It sounds very owl-like, but after researching the vocalizations of all the local owl species, I can't match this vocal to any of their calls. I've taken to nicknaming it the "oowoo" call. And I've only heard it when other suspected sasquatch vocals or activity was occurring. Once it happened during a long series of howls, barks and whoops, last March. These oowoo calls occured at 10:31pm, just over an hour after the bipedal walkup:

http://sites.google.com/site/mongahela/myrecordings2011/WS500017-03-OoWooVocals-HP.mp3


Finally, 10 minutes after the oowoo vocals, a mysterious series of loud bangs was heard. The first two happen at 10:41pm and come from the deep valley to the north. They are far enough away that some echo from an adjacent mountain side is detectable. About a minute after these first two bangs, three louder, closer bangs ring out, closer to the mic, but still from the deep valley to the north. The sound as if they are a response to the first two bangs:

http://sites.google.com/site/mongahela/myrecordings2011/WS500017-03-BigBangs-HP.mp3


After that, the recorder picked up nothing more of interest

Differentiating quadrupedal and bipedal footsteps in spectrograms

I had a couple of comments about the nature of footfalls in a clip shared on March 31st, so I thought I'd try to illustrate the differences between bipedal and quadrupedal walking in audio recordings. First thing to remember is not every leafy sound you hear in a recording like this is a step. Sometimes shuffling feet will cause extra leaf noise that obscures a step, or make a sound like multiple steps. Second thing to know is steps in a spectrogram appear as tall vertical bars with each foot impact.

The big difference between bipedal and quadrupedal steps is the pace or timing with which the feet strike the ground. Healthy bipedal steps (with no limp) are regularly spaced one from the other. They really only change their relationship when the walker's pace quickens or slows. Here's an example of bipedal steps in a spectrogram (my own steps in fact). Notice how evenly spaced the numbered steps are:

https://picasaweb.google.com/lh/photo/4l06zp-Imbw3XIkEQ08TtA?feat=directlink

Quadrupedal steps on the other hand are rarely ever so evenly spaced. Instead you'll find a walking quadrupeds steps tend to group into tight pairs, 1-2, 3-4. And when they do step evenly its not a pace that's maintained for long, the quadrupedal "lope" quickly returns. Here's a spectrogram of a quadruped walking past my recorder in the night. Note the pairing of steps:

https://picasaweb.google.com/lh/photo/d7B-ZBeioD9DyFOA7dPZVg?feat=directlink

So with that in mind, take a look at the spectrogram of the foot falls as they approach in the recording shared on March 31st. The vertical bars are fainter because the walker is farther from the mic. But notice how evenly spaced they are, as opposed to grouped up in pairs:

https://picasaweb.google.com/lh/photo/7HPqOXyk1hYDDhOLnTrBiA?feat=directlink

It's been a whole winter since I could get out and leave a recorder in my research area over night. Happily I did so Friday of last week and while it was deathly quiet on two of my three recorders, the third managed to capture some interesting audio. The first notable clip starts about a half hour after my friends and I dropped the recorder and walked away. In the clip below it sounds, to my ear anyway, as if something walks in through the forest to check out the area we've just vacated. This is what some folks in audio recording circles would call a "walk-up". While the clip is less than 4 minutes long, the visitor actually hangs around for close to half an hour, before subtly moving away. Take a listen to the foot steps as they approach. Do they sound bipedal, or quadrupedal to you?
http://sites.google.com/site/mongahela/myrecordings2011/WS500017-01-BipedalSteps-HP.mp3