The audio record

Sound is the evidence most people meet first. A footprint has to be found. A photograph requires a camera aimed at the right patch of ground. A scream arrives at two in the morning through a tent wall, uninvited.

It is also the evidence class with the deepest structural flaw. A microphone records air pressure. It does not record what displaced the air. Nearly every other question about a recording can in principle be settled: when it was made, whether it was cut, what equipment captured it. The question that matters, what was standing in front of the microphone, cannot be answered by the recording itself. It has to come from somewhere outside the tape, and in the famous cases it never does.

The Sierra Sounds

Ron Morehead and Al Berry recorded audio in the Sierra Nevada in the early 1970s. The dates in circulation do not agree. Wikipedia's article dates the camping trip to 1971 and the recordings discussed to 1972. Morehead's own site and the BFRO both credit Volume 1 to Berry in 1972 and Volume 2 to Morehead in the fall of 1974, from the same remote deer camp. Morehead's site states the microphone sat about 40 feet from the camp shelter. DOCUMENTED The tapes exist and have been sold commercially for decades.

Wikipedia characterizes Berry as a skeptic looking for evidence of a hoax, and quotes Morehead's blog to the effect that Berry maintained "it would have made the story even more interesting if he could have discovered how anyone could have pulled this off." Berry died in 2012.

What is audible on the tapes is not really in dispute. Two men talk quietly. Distant howls come in. The men call back and attempt to imitate them. More vocalizations follow, along with grunts and knocking. ALLEGED That the source was a non-human primate is Morehead's claim, resting on his and Berry's account of events at a location neither man has ever publicly disclosed.

The undisclosed location is not a small problem. It prevents anyone else from surveying the ground or checking who else was camped within earshot.

What the engineering study actually said

The study everyone cites is one almost nobody has read, and this entry did not read it either.

DOCUMENTED The volume it is published in exists. Manlike Monsters on Trial: Early Records and Modern Evidence, edited by Marjorie M. Halpin and Michael M. Ames, was published by the University of British Columbia Press in 1980 and collects papers from a conference titled "Sasquatch and Similar Phenomena," held in May 1978 at the UBC Museum of Anthropology. The chapter is cited everywhere as R. Lynn Kirlin and Lasse Hertel, "Estimates of Pitch and Vocal Tract Length from Recorded Vocalizations of Purported Bigfoot." R. Lynn Kirlin is a real signal-processing researcher with a long publication record. ALLEGED The chapter's presence in that volume, and the page range usually given for it, could not be confirmed against a table of contents or the book itself for this entry, so no page numbers are printed here. It is a conference volume from a university press, which is not the same thing as a peer-reviewed journal paper, and it should stop being described as one.

The BFRO's page on the recordings is the most specific accessible account of what the analysis found. It states that "the study concluded that the unusual vocalizations were primate in origin, and that at least one of the voices exceeded normal human ranges." It also states, in the next sentence, that "although the study did not rule out the possibility of human source, it established that the vocalizations were spontaneous at the time of recording and that there was no evidence of pre-recording or re-recording at altered tape speed."

CONTESTED Proponents quote the tape-speed clause constantly and the human-source clause almost never. Both are in the same sentence. Tape speed manipulation was excluded. A large man with an unusual voice was not.

The famous numbers attached to this study, a specific height range in feet and inches and a specific count of distinct speakers, are not printed here. They appear in secondary summaries; they were not found in any source opened for this entry, including the BFRO page and Wikipedia, and the chapter text was not obtained. A figure that cannot be traced to its source is not a figure.

Grover Krantz, the Washington State University physical anthropologist who taught there from 1968 to 1998 and spent much of his career arguing that sasquatch probably exists, examined the audio claims in Big Footprints (Johnson Books, Boulder, 1992). As the linguist Mark Newbrook quotes him, Krantz found "no compelling reason to believe that any of [the recordings in question] are what the recorders claimed them to be," and was told by one of the very university sound specialists cited in support of the recordings that humans could easily imitate such sounds. That is the field's most prominent academic proponent declining to accept its most famous tape. This entry has not read Krantz directly and relies on Newbrook's quotation of him.

Why body size cannot be read off a voice

The finding that undercuts the height inference comes from mainstream bioacoustics and has nothing to do with Bigfoot.

Formant frequencies do scale with vocal tract length, and vocal tract length does scale with body size, within a species. Across species the link is not reliable, because animals cheat. W. Tecumseh Fitch and David Reby published "The descended larynx is not uniquely human" in Proceedings of the Royal Society B in 2001 (volume 268, issue 1477, pages 1669 to 1675). DOCUMENTED They documented descended larynges in red and fallow deer, noting that the resting position of the larynx in males of those species is similar to that in humans, and that red deer stags lower the larynx further, to the sternum, while roaring. The authors suggest that laryngeal descent elongates the vocal tract and allows callers to exaggerate their perceived body size by lowering resonant frequencies. The one anatomical trick that makes "vocal tract length implies a giant" fail is a trick that evolved specifically to make listeners believe there is a giant.

The mistake runs in the other direction too. A bull elk weighs several hundred pounds and produces a bugle reaching about 4,000 Hz by blowing air from the glottis through the nasal cavities, and can also produce deeper sounds near 150 Hz using the larynx. Wikipedia's summary of the literature calls that high frequency "unusual for a vocalization produced by a large animal," which is the point. Pitch and formants are produced by anatomy and behavior, not by mass. A big animal can shriek. A medium animal can boom.

None of this proves the Sierra Sounds are human. It removes the inference that they cannot be.

Samurai chatter

The most argued-over segment is a run of rapid clipped syllables nicknamed "samurai chatter" for its resemblance to dialogue in old Japanese samurai films. Morehead describes it as language.

ALLEGED Scott Nelson, described by Karen Stollznow in Scientific American as "a retired U.S. Navy Cryptologic Technician Interpreter who speaks Russian, Spanish and Persian," treats the recordings as linguistic data and built a transcription scheme for them, which Newbrook reports Nelson calls the Sasquatch Phonetic Alphabet, or more formally the Unidentified Hominid Phonetic Alphabet. Widely repeated quotations in which Nelson declares the material definitely a language, definitely not human in origin, and impossible to fake trace to a local newspaper piece that no longer resolves online, and are not reproduced here. The one Nelson statement this entry could verify is the opening premise Stollznow quotes: "The existence of the Sasquatch Being is hereby assumed, since any creature must exist before his language."

CONTESTED Linguists have responded in print. Newbrook, writing at Skeptical Humanities on July 7, 2013, questioned the use of an idiosyncratic English-derived system in place of the International Phonetic Alphabet, observed that "the phonology of Bigfoot-language, if the language is genuine, appears implausibly similar to those of Indo-European languages and in particular to that of English," and noted that "crypto-linguist," as applied to Nelson, "seems to refer to a person with skills in interpreting (and perhaps analysing) oral linguistic data heard or recorded in difficult conditions, rather than to a person with training or proficiency in linguistics." Stollznow, who holds a Ph.D. in linguistics from the University of New England in Australia, wrote in Scientific American on July 24, 2013 that "bilingualism (speaking two or more languages) and working as a translator doesn't qualify someone to identify or describe undocumented languages," judged the Sierra Sounds "a combination of hoax and misidentification," and wrote that "it is obvious that other animals made some of the sounds, such as bears."

There is a logical trap in transcription work worth naming. A phonetic alphabet will write down any sound it is designed to accept. Building a system flexible enough to transcribe the tape, then transcribing the tape, demonstrates that the system works. It does not demonstrate meaning, syntax, or a vocal tract. A transcript is not a language.

Wood knocking

ALLEGED Wood knocking, audible blows struck against trunks, is widely claimed as sasquatch communication and is used as a field technique by several research groups. The behavior has a real primate precedent. Vesta Eleuteri and colleagues, publishing in Animal Behaviour in 2022 (volume 192, pages 189 to 205), studied buttress drumming in the Waibira chimpanzee community in Uganda's Budongo Forest. DOCUMENTED Chimpanzees drum on the buttress roots of trees, generating low-frequency sounds that can reach distances of over 1 km. The authors found individual differences in drumming bouts produced by seven males during travel events, and no evidence of individual differences in bouts produced by four males during displays, concluding that chimpanzees may be able to encode identity in drumming signatures.

That is what evidence for a knocking hominin would need to look like: repeated recordings, identified individuals, an observed behavioral context, and a stated null result where one was found. The Bigfoot version has none of that, and the woods are full of competing sources.

DOCUMENTED A male ruffed grouse drums by beating his wings against the air while standing on a log, stone, or mound of soil, which serves only as a stage. He does not strike it. The result is a low-frequency series that starts slow and speeds up, audible for a quarter mile (400 m) or more. A pileated woodpecker drums a fairly slow, deep roll lasting about three seconds, often on hollow trees for the most resonant sound possible. Limbs fall. Whole trees fall. In deep winter a cryoseism, or frost quake, produces a booming report, and it follows a recognizable recipe: ground saturated by thaw or rain before a cold air mass arrives, less than six inches (15 cm) of insulating snow, and a rapid temperature drop from approximately freezing to near or below −18 °C (0 °F) on a timescale of 16 to 48 hours, most likely between midnight and dawn.

Then there is the physics. A knock is a brief impulse. It carries far less information than a sustained call, which has formants, harmonics and modulation that can narrow a source. A single isolated bang is close to the worst possible signal for identifying what produced it.

What actually screams in the woods

The fox row deserves a caveat, because the popular explanation and the reference literature do not match. CONTESTED British wildlife sources, including the Wildlife Trust for Lancashire, Manchester and North Merseyside, describe the scream that sounds like a woman in pain as a vixen advertising that she is ready to mate, answered by the dog fox's "hup-hup-hup" bark. Wikipedia's red fox article, summarizing the behavioral literature, assigns a "ululating siren-like shriek" to a submissive fox approached by a dominant animal, and separately notes that the "wow wow wow" call is heard most frequently from December to February. Those are not the same claim. What is well supported is that red foxes are loud in winter, that the noise is routine social and breeding behavior rather than an animal being killed, and that no US wildlife agency source confirming the popular mating-call version was located for this entry.

The cougar is heard far less often than it is blamed. Miguel Ordeñana of the Natural History Museum of Los Angeles County has written that "even expert trackers almost never observe the cats vocalizations, limiting puma vocal communication research to captive pumas."

Nobody counts voices correctly

Brian Mitchell, an adjunct professor at the University of Vermont who spent seven years on coyote vocal communication for his doctoral research at Berkeley, writing in Northern Woodlands on February 24, 2014, describes the beau geste effect. People hearing coyotes assume a large pack, but "this is an auditory illusion." Because of the variety of sounds each coyote produces, and the way sound is distorted as it passes through the environment, "two of these tricksters can sound like seven or eight animals." DOCUMENTED

That is a documented failure of human auditory judgment about a common, well-studied species. A listener who cannot count coyotes should hold loose opinions about the species of an unfamiliar night sound, and looser ones about its size.

Why provenance is the wall

Forensic audio can establish a great deal about a file and nothing about an animal. Authentication asks whether a recording is unedited and made when its owner says. Identification asks what made the sound. The first never delivers the second.

Even a flawless authentication of the Sierra Sounds would prove that two men recorded something at an undisclosed place on a disputed date, unedited. It would not exclude a person off-microphone, a bear, an elk, or an owl. CONTESTED This is why the audio record has grown enormous without advancing: adding recordings adds volume, not provenance.

A recording could matter. One made at a disclosed location, alongside independently verified physical evidence, with the source visually confirmed by a second party, would be a genuine datum. ALLEGED Every claimed sasquatch vocalization in circulation is missing at least one of those three conditions, and usually all three. Wikipedia's article on the Sierra Sounds states flatly that "no studies have been conducted on the Sierra Sounds in mainstream scholarly sources," and no later bioacoustic study of purported sasquatch vocalizations in a peer-reviewed venue was located for this entry.

If you hear something

1. Write down the clock time to the minute and the air temperature. Both narrow the candidate list faster than any description of the sound.
2. Note the compass bearing, then distrust your distance estimate. Canopy and terrain scatter sound badly.
3. Count syllables and clock the rhythm. Eight accented hoots is a barred owl. A slow accelerating thump is a grouse.
4. Check the calendar. Late August into fall means elk. Winter nights mean fox. A hard overnight freeze on wet, thinly covered ground means frost quakes.
5. Keep recording after it stops. The second call, the answer, and the silence are often more diagnostic than the sound that startled you.
6. Compare against a reference archive of recorded calls before comparing against anything else. Most sounds resolve there.

A sound you cannot identify is a sound you cannot identify. That is an honest place to stop, and it is where this evidence class ends.

Sources

• Wikipedia, "Sierra Sounds," accessed September 2026 (source for the 1971 trip and 1972 recording dates, Berry's skepticism, Berry's death in 2012, the undisclosed location, and the statement that no studies have been conducted in mainstream scholarly sources). https://en.wikipedia.org/wiki/Sierra_Sounds
• Ron Morehead, "About Bigfoot Recordings," ronmorehead.com, accessed September 2026 (Volume 1 credited to Al Berry, 1972; Volume 2 to Morehead, 1974; microphone about 40 feet from the camp shelter). This page makes no mention of the University of Wyoming analysis. https://ronmorehead.com/about-bigfoot-recordings/
• Bigfoot Field Researchers Organization, "The Bigfoot Recordings, Volume 2," accessed September 2026 (source of the quoted findings that the study concluded the vocalizations were "primate in origin," that "at least one of the voices exceeded normal human ranges," that the study "did not rule out the possibility of human source," and that there was "no evidence of pre-recording or re-recording at altered tape speed"). This page names no author and gives no height figures or speaker count. https://www.bfro.net/avevid/SierraSounds/BigfootRecordings.asp
• Marjorie M. Halpin and Michael M. Ames, eds., Manlike Monsters on Trial: Early Records and Modern Evidence, University of British Columbia Press, 1980, 336 pp., from the conference "Sasquatch and Similar Phenomena," May 1978, UBC Museum of Anthropology. Volume and conference verified via the Internet Archive record. https://archive.org/details/manlikemonsterso0000unse
• R. Lynn Kirlin and Lasse Hertel, "Estimates of Pitch and Vocal Tract Length from Recorded Vocalizations of Purported Bigfoot," cited as a chapter in the above. Neither the chapter text nor a table of contents confirming its page range was obtained for this entry, so no page numbers are asserted. R. Lynn Kirlin's existence as a signal-processing researcher was confirmed via his DBLP author record. https://dblp.org/pid/14/6547.html
• W. Tecumseh Fitch and David Reby, "The descended larynx is not uniquely human," Proceedings of the Royal Society B 268, no. 1477 (2001): 1669–1675. DOI 10.1098/rspb.2001.1704. Abstract read in full. https://pmc.ncbi.nlm.nih.gov/articles/PMC1088793/
• Mark Newbrook, "Linguistics 'Hall of Shame' 17," Skeptical Humanities, July 7, 2013 (source of the Newbrook quotations, the description of Nelson's transcription system, and the Grover Krantz quotation from Big Footprints, Johnson Books, Boulder, 1992, pp. 133–134, which was not read directly). https://skepticalhumanities.com/2013/07/07/linguistics-hall-of-shame-17/
• Karen Stollznow, "(Big)foot in Mouth: Bigfoot Language," Scientific American, July 24, 2013 (source for Scott Nelson's description as a retired U.S. Navy Cryptologic Technician Interpreter, the Nelson quotation, and Stollznow's own credentials). https://www.scientificamerican.com/blog/mind-guest-blog/bigfoot-in-mouth-bigfoot-language/
• Wikipedia, "Grover Krantz," accessed September 2026 (Washington State University, 1968–1998; Big Footprints publication details). https://en.wikipedia.org/wiki/Grover_Krantz
• Vesta Eleuteri, Maddison Henderson, Adrian Soldati, Guy Badihi, Klaus Zuberbühler and Catherine Hobaiter, "The form and function of chimpanzee buttress drumming," Animal Behaviour 192 (2022): 189–205. Abstract read in full via the University of St Andrews research repository. https://research-repository.st-andrews.ac.uk/handle/10023/26186
• Brian Mitchell, "Coyotes: Listening to Tricksters," The Outside Story, Northern Woodlands, February 24, 2014. https://northernwoodlands.org/outside_story/article/coyotes
• Miguel Ordeñana, "The Sound of Our Griffith Park Mountain Lion: P-22 and the Mysteries of Puma Communication," Natural History Museum of Los Angeles County. https://nhm.org/stories/sound-our-griffith-park-mountain-lion-p-22-and-mysteries-puma-communication
• The Wildlife Trust for Lancashire, Manchester and North Merseyside, "The secret lives of foxes." A British source, cited here only as the popular mating-call account, not as evidence about North American foxes. https://www.lancswt.org.uk/blog/secret-lives-foxes
• Wikipedia, "Red fox," accessed September 2026 (the "ululating siren-like shriek" of a submissive fox, the December to February "wow wow wow" call, and winter breeding). https://en.wikipedia.org/wiki/Red_fox
• Wikipedia, "Barred owl," accessed September 2026 (eight accented hoots, the mnemonic, cackles and gurgles, and calls that "probably carry well over 0.8 km"). https://en.wikipedia.org/wiki/Barred_owl
• Wikipedia, "Cougar," accessed September 2026 (cannot roar; caterwauls, yowls, growls, spits, snarls, hisses, whistles, chirps and mews). https://en.wikipedia.org/wiki/Cougar
• Wikipedia, "Elk," accessed September 2026 (bugle at about 4,000 Hz via glottis and nasal cavities, 150 Hz laryngeal sounds, "unusual for a vocalization produced by a large animal," rut beginning late August). https://en.wikipedia.org/wiki/Elk
• Wikipedia, "Ruffed grouse," accessed September 2026 (does not strike the log; quarter mile / 400 m). https://en.wikipedia.org/wiki/Ruffed_grouse
• Wikipedia, "Pileated woodpecker," accessed September 2026 (about a three-second roll, hollow trees for resonance). https://en.wikipedia.org/wiki/Pileated_woodpecker
• Wikipedia, "Cryoseism," accessed September 2026 (saturation, under six inches of snow, drop to near or below −18 °C over 16 to 48 hours, midnight to dawn). https://en.wikipedia.org/wiki/Cryoseism

Not used, and why: a widely repeated Scott Nelson quotation traced to a February 2019 Hastings Tribune article whose URL no longer resolves; the "fisher cat scream" explanation, for which no state wildlife agency source was found; and specific height and speaker-count figures attributed to the Kirlin and Hertel chapter, which appear only in secondary summaries that could not be opened for this entry.