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
Sunday, May 15, 2011
Friday, April 1, 2011
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
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
Thursday, March 31, 2011
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
http://sites.google.com/site/mongahela/myrecordings2011/WS500017-01-BipedalSteps-HP.mp3
Monday, August 23, 2010
Something Big Moved in the Piney Woods
This report was originally published June 6, 2010 in the BFRO Discussion Forums.
On the evening of May 15th of this year I had just finished deploying a parabolic mic and recorder in a new area, about a mile east of where I normally set it up and let it run unattended. As I drove back out of the area I decided to stop at a dense piney wood that overlooked two important features of my research area. In one direction it looks over the valley where I normally establish my camp. In the other direction it overlooks the valley where I deploy the parabolic. In past visits to this region I've heard vocalizations from this part of the forest, while I sat by my fire in the valley below. And my parabolic has captured hours of vocalizations from the valley where its normally deployed, and done so consistently over the last few months.
So as the sun was setting I thought it would be a good idea to park my truck along a lonely stretch of abandoned dirt road, deep in a desolate forest, and walk into one of its darkest recesses. I looked at the sky as I walked away from my vehicle and decided I had about enough light for a 30 minute sojourn, so I didn't wear a head lamp assuming I wouldn't get far from the truck.
I walked into the edge of the piney woods and then turned left to skirt along the inside of its edge, keeping to the high ground and allowing the deepest recesses of the piney woods to pass below me, on my right. I seemed to locate a vague passage through the pines (or more properly, red spruce) that had been planted by the CCC about 80 years earlier. The path looked like the remnant of an old logging railway, probably more than 100 years old, which made sense given how the terrain around me laid out.
I followed that wide, level, gently curving path for about 150 yards stopping frequently to listen, attempt an occasional soft whoop, and do a few soft wood knocks with my trusty little-league hickory baseball bat. On the way out along this path I didn't hear anything that gave me any sense that I was not alone and eventually I hit a natural turn around point where brush blocked my way, so I turned back.
I should mention that as I hike around in the woods I've taken to placing my digital recorder in a small back pack that I carry. Extending from the recorder are two sensitive microphones, omni-directional, that I can clip to the shoulder straps of the pack. They're stereo mics so naturally I clip them to the left and right to keep the sound scape properly oriented while I'm recording. I also carry a bottle of water in that pack, and on occasion, hearing an abrupt sloshing sound from directly behind, can be a bit unnerving (especially when your senses are keyed up).
So now I've reversed my direction, and the deep center of the piney woods is on my left. Occasionally I hear a squeak-like sound that I attribute to trees rubbing against each other in the slight evening breeze. I repeat the process on the way out, making soft knocks and subdued whoops, but I can't hear any response when I pause to listen quietly. As I'm closing the last 50 yards to the truck, and crunching along through the leaves of last autumn, I hear a loud and familiar vocalization from the rise of land directly ahead. It sounds like the Big Owl vocals that I've recorded in March, April and now May of this year.
This is where the audio clip below begins. I paused to listen and speaking to myself, make note of the vocal (this sounds crazy, but it helps a lot when post processing audio, the trick is not to be too chatty and avoid stepping on incoming vocals). I hold my position and within a few seconds the vocal repeats, this time it sounds softer but at least its not blocked by the sounds of my foot steps. This is when I start to suspect it is one of the vocalizers I recorded back in March.
I resumed my trek back to my truck, its not far now, and as I walk a third vocal rings out from the high ground ahead. Unfortunately my foot steps obscure it, but by now I'm looking for the relative familiarity of my vehicle. As I draw close, I decide I should do a whoop and wood knock in response to those vocals. I did a moderate whoop first, with no real effect (other than the vocalizer never vocalized again afterward). A short time later I tried a wood knock. Maybe it was the knock, or maybe the whoop and later knock, or maybe my after shave, I don't know, but this seemed to trigger a response.
As I stood quietly, downhill, to my left and deep into the piney woods, I heard something big move in the forest. My ears told me this was large, and as it moved for a few seconds I heard a stick break. The audio recorder heard this as well, and more. I held my position, listening for more movement in the rapidly gathering gloom. None came, and I hear nothing more, but my sense of unease elevated dramatically and I decided it was time to leave a gift and get out. I went straight to my truck, pulled out some Walmart apples and oranges, and left them out of sight of the road before leaving.
This is where I should have held pat, maybe open the tailgate of my truck and sit and listen for a while. But I'd had enough solo squatching for the evening and I just didn't think hanging around would be very productive. So I rode off down the road and checked out a few new locations where I thought I might get some returns to my knocks or vocals.
I've edited the entire 30 minute walk down to under 60 seconds, to focus on the key auditory events of that evening. In addition to the movement to my left, the mics also picked up a substantial grunt/growl from the same direction, and just before the end of the clip, some soft rapid stick knocking sounds, seemingly from somewhere behind me.
The clip, and the transcript are as follows:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310089-AMLPHPNRAMCOPEAK-study.mp3
(as always, your listening satisfaction will be best from a decent pair of headphones)
0:00-0:02 - my footsteps in the leaves
0:02 - vocalization, obscured by foot steps
0:08 - I say "that was a vocal"
0:12 - vocal repeats
0:14 - "and a second vocal"
0:17 - audio splice
0:20 - vocalization, obscured by foot steps
0:22 - "and a third vocal"
0:26 - audio splice
0:28 - my wood knock
0:45 - stick break and movement from left
0:47 - louder movement from left (slightly audible in right channel, too)
0:50 - grunt/growl from left
0:50-0:57 - light stick tapping possibly from behind (audible in both channels)
On the evening of May 15th of this year I had just finished deploying a parabolic mic and recorder in a new area, about a mile east of where I normally set it up and let it run unattended. As I drove back out of the area I decided to stop at a dense piney wood that overlooked two important features of my research area. In one direction it looks over the valley where I normally establish my camp. In the other direction it overlooks the valley where I deploy the parabolic. In past visits to this region I've heard vocalizations from this part of the forest, while I sat by my fire in the valley below. And my parabolic has captured hours of vocalizations from the valley where its normally deployed, and done so consistently over the last few months.
So as the sun was setting I thought it would be a good idea to park my truck along a lonely stretch of abandoned dirt road, deep in a desolate forest, and walk into one of its darkest recesses. I looked at the sky as I walked away from my vehicle and decided I had about enough light for a 30 minute sojourn, so I didn't wear a head lamp assuming I wouldn't get far from the truck.
I walked into the edge of the piney woods and then turned left to skirt along the inside of its edge, keeping to the high ground and allowing the deepest recesses of the piney woods to pass below me, on my right. I seemed to locate a vague passage through the pines (or more properly, red spruce) that had been planted by the CCC about 80 years earlier. The path looked like the remnant of an old logging railway, probably more than 100 years old, which made sense given how the terrain around me laid out.
I followed that wide, level, gently curving path for about 150 yards stopping frequently to listen, attempt an occasional soft whoop, and do a few soft wood knocks with my trusty little-league hickory baseball bat. On the way out along this path I didn't hear anything that gave me any sense that I was not alone and eventually I hit a natural turn around point where brush blocked my way, so I turned back.
I should mention that as I hike around in the woods I've taken to placing my digital recorder in a small back pack that I carry. Extending from the recorder are two sensitive microphones, omni-directional, that I can clip to the shoulder straps of the pack. They're stereo mics so naturally I clip them to the left and right to keep the sound scape properly oriented while I'm recording. I also carry a bottle of water in that pack, and on occasion, hearing an abrupt sloshing sound from directly behind, can be a bit unnerving (especially when your senses are keyed up).
So now I've reversed my direction, and the deep center of the piney woods is on my left. Occasionally I hear a squeak-like sound that I attribute to trees rubbing against each other in the slight evening breeze. I repeat the process on the way out, making soft knocks and subdued whoops, but I can't hear any response when I pause to listen quietly. As I'm closing the last 50 yards to the truck, and crunching along through the leaves of last autumn, I hear a loud and familiar vocalization from the rise of land directly ahead. It sounds like the Big Owl vocals that I've recorded in March, April and now May of this year.
This is where the audio clip below begins. I paused to listen and speaking to myself, make note of the vocal (this sounds crazy, but it helps a lot when post processing audio, the trick is not to be too chatty and avoid stepping on incoming vocals). I hold my position and within a few seconds the vocal repeats, this time it sounds softer but at least its not blocked by the sounds of my foot steps. This is when I start to suspect it is one of the vocalizers I recorded back in March.
I resumed my trek back to my truck, its not far now, and as I walk a third vocal rings out from the high ground ahead. Unfortunately my foot steps obscure it, but by now I'm looking for the relative familiarity of my vehicle. As I draw close, I decide I should do a whoop and wood knock in response to those vocals. I did a moderate whoop first, with no real effect (other than the vocalizer never vocalized again afterward). A short time later I tried a wood knock. Maybe it was the knock, or maybe the whoop and later knock, or maybe my after shave, I don't know, but this seemed to trigger a response.
As I stood quietly, downhill, to my left and deep into the piney woods, I heard something big move in the forest. My ears told me this was large, and as it moved for a few seconds I heard a stick break. The audio recorder heard this as well, and more. I held my position, listening for more movement in the rapidly gathering gloom. None came, and I hear nothing more, but my sense of unease elevated dramatically and I decided it was time to leave a gift and get out. I went straight to my truck, pulled out some Walmart apples and oranges, and left them out of sight of the road before leaving.
This is where I should have held pat, maybe open the tailgate of my truck and sit and listen for a while. But I'd had enough solo squatching for the evening and I just didn't think hanging around would be very productive. So I rode off down the road and checked out a few new locations where I thought I might get some returns to my knocks or vocals.
I've edited the entire 30 minute walk down to under 60 seconds, to focus on the key auditory events of that evening. In addition to the movement to my left, the mics also picked up a substantial grunt/growl from the same direction, and just before the end of the clip, some soft rapid stick knocking sounds, seemingly from somewhere behind me.
The clip, and the transcript are as follows:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310089-AMLPHPNRAMCOPEAK-study.mp3
(as always, your listening satisfaction will be best from a decent pair of headphones)
0:00-0:02 - my footsteps in the leaves
0:02 - vocalization, obscured by foot steps
0:08 - I say "that was a vocal"
0:12 - vocal repeats
0:14 - "and a second vocal"
0:17 - audio splice
0:20 - vocalization, obscured by foot steps
0:22 - "and a third vocal"
0:26 - audio splice
0:28 - my wood knock
0:45 - stick break and movement from left
0:47 - louder movement from left (slightly audible in right channel, too)
0:50 - grunt/growl from left
0:50-0:57 - light stick tapping possibly from behind (audible in both channels)
Sunday, August 15, 2010
Horn-like Vocals
Personal matters have kept me out of the field for much of this summer, and will do so at least through the end of September. I haven't been back to my study area since the 2nd of July when I downloaded audio from my long duration recorder, then left it redeployed with fresh batteries. I hope a bear hasn't found it and ripped it off the tree by now. It's got another 6 weeks of hanging out before I'll be able to go back and check on it.
But I couldn't stand not having a recorder in the field so I ordered a new one, the Olympus WS-510M, bought a new set of mics from Giant Squid Audio Lab, and went for a hike deep into a regional park not far from my house. I like the looks of this park because its sandwiched between a large river and a sprawling neighborhood of housing developments. The rivers edge is completely undeveloped for miles in either direction and thickly forested with large, old growth timber. There are a number of hiking, biking, and horse trails through the park, but they're closed at night and a lot of the park is strictly bush whacking if you want to get in to see it. The river defining one edge of the park is broad, but wade-able at many places and has several uninhabited islands in mid-stream. On the opposite shore of the river is more parkland, a wildlife management area full of swamps, and miles of undeveloped farm land (as opposed to the neighborhoods on my side of the river).
Its only 20 minutes from my house so I figured, what the heck. You never know until you go. So yesterday afternoon I hiked a half mile in on foot trails and then bush whacked a hundred yards off trail and into a thick understory of white oak saplings. I stopped at the end of a finger ridge that looked out over the heavily forested river bottom. I could hear the river rapids below, about a quarter mile away, and the occasional passing aircraft engine.
I deployed the recorder in one of the saplings with the left channel mic pointed toward the river, and the right channel mic pointed back toward the parking lot where I'd come from. It was about 7 p.m. with plenty of day light left, but before walking away I did three whoop and wood knock combinations.
This morning I returned before lunch to pick up the recorder. The battery appeared to have run out by the time I picked it up, which is the norm. The recorder indicated 14 hours of audio had been captured, so I was pleased that I would have plenty of recording to search through. But when I got it downloaded onto my computer I was dismayed to see that something strange had happened. The recorder captured about 55 minutes of audio, then seemed to pause for a dozen hours, and then continued recording two more hours of audio early this a.m. Not sure why this happened but hope its not a flaw in this new recorder.
Anyway, after going through the three hours of audio it did capture, I managed to locate a couple of interesting clips to share.
The first is a pair of faint whoops that occurred early in the morning hours, right around sun up. They're faint (as are many of the calls I seem to capture), but they were noticeable in the spectrogram software I use to review audio (I would have completely missed these if it weren't for the spectrogram. The first whoop seems to be preceded by a soft wood knock, the repeating down note of a yellow-billed cuckoo appears, and at the end the second whoop sounds nearly the same as the first, just fainter. I put this into a youtube video with annotations to hopefully make it more discernible to your ear (looping the video can help you hear the whoops more clearly):
The second recording might not be a vocalization at all, but its note-worthy enough that I want to share it, and some examples of similar recordings. I call it a "horn" like vocalization. It sounds rather mechanical in origin, but its also very similar to other horn-like vocals recorded by Galahad in Washington State. His recordings sound like a car or fog horn at first, but sometimes waivers in a distinctly biological fashion, sounding natural and not mechanical in origin. The horn-like sound my recorder captured this morning was some time before sunrise, seems to be preceded by a deep wood knock, and also seems to evoke a wood knock response about 15 seconds later (its that wood knock that made me look closer at the possible vocal).
Warning, this horn-like sound is such a low frequency, 265 Hz, that your computer speakers may won't be able to reproduce it (my laptop speakers can't). So head phones are probably required in order for you to hear the note at all (but the wood knock at the end of the clip is easily heard).
Here's a link to the youtube video of this sound in a spectrogram:
And here's a couple of links to Galahad's horn vocals from Washington state, for comparison (these are higher frequency and easily discernible on most computer speakers):
http://sites.google.com/site/mongahela/galahad/GHB-R09_0091-AMNRLPAM-StrangeHowl.mp3
http://sites.google.com/site/mongahela/galahad/GHB-R09_0060-AMNRLPAM-HornVocal.mp3
But I couldn't stand not having a recorder in the field so I ordered a new one, the Olympus WS-510M, bought a new set of mics from Giant Squid Audio Lab, and went for a hike deep into a regional park not far from my house. I like the looks of this park because its sandwiched between a large river and a sprawling neighborhood of housing developments. The rivers edge is completely undeveloped for miles in either direction and thickly forested with large, old growth timber. There are a number of hiking, biking, and horse trails through the park, but they're closed at night and a lot of the park is strictly bush whacking if you want to get in to see it. The river defining one edge of the park is broad, but wade-able at many places and has several uninhabited islands in mid-stream. On the opposite shore of the river is more parkland, a wildlife management area full of swamps, and miles of undeveloped farm land (as opposed to the neighborhoods on my side of the river).
Its only 20 minutes from my house so I figured, what the heck. You never know until you go. So yesterday afternoon I hiked a half mile in on foot trails and then bush whacked a hundred yards off trail and into a thick understory of white oak saplings. I stopped at the end of a finger ridge that looked out over the heavily forested river bottom. I could hear the river rapids below, about a quarter mile away, and the occasional passing aircraft engine.
I deployed the recorder in one of the saplings with the left channel mic pointed toward the river, and the right channel mic pointed back toward the parking lot where I'd come from. It was about 7 p.m. with plenty of day light left, but before walking away I did three whoop and wood knock combinations.
This morning I returned before lunch to pick up the recorder. The battery appeared to have run out by the time I picked it up, which is the norm. The recorder indicated 14 hours of audio had been captured, so I was pleased that I would have plenty of recording to search through. But when I got it downloaded onto my computer I was dismayed to see that something strange had happened. The recorder captured about 55 minutes of audio, then seemed to pause for a dozen hours, and then continued recording two more hours of audio early this a.m. Not sure why this happened but hope its not a flaw in this new recorder.
Anyway, after going through the three hours of audio it did capture, I managed to locate a couple of interesting clips to share.
The first is a pair of faint whoops that occurred early in the morning hours, right around sun up. They're faint (as are many of the calls I seem to capture), but they were noticeable in the spectrogram software I use to review audio (I would have completely missed these if it weren't for the spectrogram. The first whoop seems to be preceded by a soft wood knock, the repeating down note of a yellow-billed cuckoo appears, and at the end the second whoop sounds nearly the same as the first, just fainter. I put this into a youtube video with annotations to hopefully make it more discernible to your ear (looping the video can help you hear the whoops more clearly):
The second recording might not be a vocalization at all, but its note-worthy enough that I want to share it, and some examples of similar recordings. I call it a "horn" like vocalization. It sounds rather mechanical in origin, but its also very similar to other horn-like vocals recorded by Galahad in Washington State. His recordings sound like a car or fog horn at first, but sometimes waivers in a distinctly biological fashion, sounding natural and not mechanical in origin. The horn-like sound my recorder captured this morning was some time before sunrise, seems to be preceded by a deep wood knock, and also seems to evoke a wood knock response about 15 seconds later (its that wood knock that made me look closer at the possible vocal).
Warning, this horn-like sound is such a low frequency, 265 Hz, that your computer speakers may won't be able to reproduce it (my laptop speakers can't). So head phones are probably required in order for you to hear the note at all (but the wood knock at the end of the clip is easily heard).
Here's a link to the youtube video of this sound in a spectrogram:
And here's a couple of links to Galahad's horn vocals from Washington state, for comparison (these are higher frequency and easily discernible on most computer speakers):
http://sites.google.com/site/mongahela/galahad/GHB-R09_0091-AMNRLPAM-StrangeHowl.mp3
http://sites.google.com/site/mongahela/galahad/GHB-R09_0060-AMNRLPAM-HornVocal.mp3
Saturday, August 14, 2010
Sasquatch Bioacoustic Blog Launched
This is the inaugural post of a blog devoted to the bioacoustic analysis of audio signals potentially originating from sasquatch.
Sasquatchbioacoustic.blogspot.com will serve as the blog discussion locale for audio analysis and bioacoustic musings of recordings collected by contributing members of the informal research community.
Earlier posts from the audio signal collection hosted at http://sites.google.com/site/mongahela/ will be migrated here for maintenance and discussion.
Sasquatchbioacoustic.blogspot.com will serve as the blog discussion locale for audio analysis and bioacoustic musings of recordings collected by contributing members of the informal research community.
Earlier posts from the audio signal collection hosted at http://sites.google.com/site/mongahela/ will be migrated here for maintenance and discussion.
Thursday, July 29, 2010
Wood Knocks in Communication
I tend to believe wood knocks are used in a range of manners to convey different messages based upon context.
Single loud wood knocks, coupled with a loud whoop or other vocal, could be a "tag-up" if you will. Maybe they ask the question "is there any body out there?!" The wood knock portion of a knock/vocal combination could serve two purposes, the first being punctuation "!", and the second being confirmation (that I am indeed a member of your species, and not some other animal vocalizing in the wilderness).
Softer wood knocks seem to be used as a means of keeping track of each other when in close proximity, and/or when danger may be near. Making a milder warning knock that your buddies a few hundred feet away can hear seems wiser than a loud bash, that would also alert the source of danger to your presence.
Here's a recording that includes a soft whoop, and subtle wood knocks, that might be an example of this kind of situation:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310076-03-AMNRLPAM-WhoopKnocksShort.mp3
Then even softer knocks may be used for still stealthier communication, possibly when danger is very near, or tension is high. I recorded some fast, soft "stick" knocks just seconds after something moved in the forest near me, and grunted audibly. The knocks sound very tense and can be heard at the very end of this recording:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310089-AMLPHPNRAMCOPEAK-study.mp3
And then there seems to be the intimidation type of wood knock, which forum member uluax actually observed being made in his remarkable class A sighting from Colorado. I don't have the link to that report handy though.
So in general, I don't think we should attach just one reason or meaning to the existence of wood knocks. Their use is probably more complex than we currently understand, and only time spent recording, studying, and learning them will improve that understanding.
But in terms of a component of communication, the inclusion of wood knocks to enhance vocals is a fascinating advance to consider. A rudimentary technology to be sure, but the mastery of a technology none the less.
Single loud wood knocks, coupled with a loud whoop or other vocal, could be a "tag-up" if you will. Maybe they ask the question "is there any body out there?!" The wood knock portion of a knock/vocal combination could serve two purposes, the first being punctuation "!", and the second being confirmation (that I am indeed a member of your species, and not some other animal vocalizing in the wilderness).
Softer wood knocks seem to be used as a means of keeping track of each other when in close proximity, and/or when danger may be near. Making a milder warning knock that your buddies a few hundred feet away can hear seems wiser than a loud bash, that would also alert the source of danger to your presence.
Here's a recording that includes a soft whoop, and subtle wood knocks, that might be an example of this kind of situation:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310076-03-AMNRLPAM-WhoopKnocksShort.mp3
Then even softer knocks may be used for still stealthier communication, possibly when danger is very near, or tension is high. I recorded some fast, soft "stick" knocks just seconds after something moved in the forest near me, and grunted audibly. The knocks sound very tense and can be heard at the very end of this recording:
http://sites.google.com/site/mongahela/myrecordings2010-1/WS310089-AMLPHPNRAMCOPEAK-study.mp3
And then there seems to be the intimidation type of wood knock, which forum member uluax actually observed being made in his remarkable class A sighting from Colorado. I don't have the link to that report handy though.
So in general, I don't think we should attach just one reason or meaning to the existence of wood knocks. Their use is probably more complex than we currently understand, and only time spent recording, studying, and learning them will improve that understanding.
But in terms of a component of communication, the inclusion of wood knocks to enhance vocals is a fascinating advance to consider. A rudimentary technology to be sure, but the mastery of a technology none the less.
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