The Sound That Santos Can’t Explain

A Brazilian coastal city is haunted by mysterious noises from the sea and lights in the sky that nobody can identify.

Santos residents thought they knew their city. The beaches, the port, the predictable rhythm of coastal life. Then something changed, and now nobody’s sleeping quite as well as they used to.

The Sound From Below

The early morning hours of Saturday, November 1, 2025, brought something unexpected to Santos, Brazil. Around 2:30 AM, residents across multiple neighborhoods along the waterfront heard a sound coming from the ocean. Not the familiar crash of waves or the hum of passing boats. Something else entirely.
The noise reached people in Ponta da Praia, Gonzaga, José Menino, and the Estuário. Enough people heard it that social media lit up with reports and questions. They struggled to describe what they’d experienced. A deep rumble. A metallic creaking. Something that sounded like an enormous object moving beneath the water.
One Gonzaga resident tried to put words to it. The sound was like something breathing, but massive. It didn’t match anything recognizable. Not a boat. Not wind. Just this presence of sound that filled the darkness. Another resident from Ponta da Praia said she’d heard similar sounds before, scattered across the years, but never this intense. The noise seemed to come from far away and also from beneath the earth, which made pinpointing a source impossible.
People started making calls. The Port Authority of Santos fielded questions from confused and concerned residents. They checked their records. No abnormalities occurred in ship movements during that time. No maneuvers scheduled or executed. No mechanical issues reported. Nothing unusual in their extensive logs of port operations.
This wasn’t the first time Santos residents had whispered about strange sounds from the ocean. For decades, people have mentioned a “sound of the breathing sea” during quiet early mornings. It’s become part of the city’s unofficial folklore, the kind of thing long-time residents mention to newcomers with a mixture of pride and unease. The noise heard on November 1st was one of the most intense manifestations of this phenomenon ever recorded in the city.

A Light That Moved Too Fast

October 2025 brought another unexplained phenomenon to Santos, and this time someone managed to capture photographic evidence. A resident named Roberta maintains a regular running routine along the beach near Canal 5. She’s out there most mornings around 5:45 AM, when the city is still mostly asleep and the light has that particular quality that early risers know well.
That morning, she saw a green light in the sky. The object moved rapidly toward Ilha das Palmas, cutting through the pre-dawn darkness with enough speed that she barely had time to process what she was seeing. She managed to pull out her phone and capture one photograph before it disappeared. Just one frame. Then nothing.
Roberta reported something else that morning, something that made the encounter even stranger. She saw what appeared to be a silhouette of a person at the water’s edge. The figure vanished at the same time as the object in the sky, as if the two phenomena were somehow connected.
Other people were present that morning. Early morning runners, beach walkers, people heading to work. They confirmed seeing the same scene play out in the sky. Multiple independent witnesses watching the same unexplained event. The sighting occurred in the same area where residents have been reporting the mysterious breathing sound from the sea, adding another layer to Santos’ growing collection of unexplained phenomena.
The green light sighting resembled another event from September 25th that had attracted attention from local residents and media outlets. The pattern was starting to become noticeable. Santos was experiencing something, and it was happening repeatedly.

The City Built Facing The Atlantic

To understand why these events matter to Santos, you need to understand the city’s relationship with the ocean. Santos was founded by Portuguese explorer Brás Cubas in 1534. Nearly five centuries later, the city has grown to about 450,000 residents, but its identity remains fundamentally tied to the Atlantic Ocean. The city’s anthem includes a line that captures everything Santos means to its people: the sea.
The Port of Santos is Latin America’s largest. During the late 19th and early 20th centuries, this port welcomed millions of immigrants whose descendants now make up much of Brazil’s population. Work on building the modern port started in 1890, transforming Santos into a major commercial hub. Through this port flowed a massive portion of Brazil’s coffee production during an era when Brazilian coffee dominated global markets. Japanese and Italian immigrants arrived by the thousands, coming to replace the recently liberated slave workforce following abolition in 1888.
Santos sits on Brazil’s southeastern coast, positioned at a crucial point where commerce, culture, and the ocean converge. The region was already a noisy area of the western South Atlantic Ocean prior to the start of deepwater oil and gas production in the Santos Basin, according to the Santos Basin Underwater Soundscape Monitoring Project. The area experiences intense traffic of commercial, military, fishing, and recreational vessels. Ships pass through constantly, creating a baseline level of underwater and surface noise that scientists have been measuring and documenting.
The two main hubs for Brazil’s export and import of goods by sea are located in this region: Santos and Rio de Janeiro ports. This constant maritime activity means the waters off Santos are never truly quiet. Which makes the mysterious breathing sound all the more remarkable. Residents who’ve lived here for decades can distinguish between normal port sounds and this other thing. They know what ships sound like. They know what weather sounds like. This is different.

A Worldwide Phenomenon

Santos isn’t alone in experiencing mysterious sounds. Residents discovering this fact often find it simultaneously comforting and disturbing. Comforting because they’re not isolated cases. Disturbing because it means this phenomenon, whatever it is, occurs across the planet. Similar sounds have been reported worldwide and researchers have given them a name: “The Hum.”
Bristol, England was one of the first places to document The Hum systematically, back in the 1970s. About 800 people in the coastal city reported hearing a steady thrumming sound that seemed to have no source. Authorities investigated. They eventually attributed the noise to a combination of vehicular traffic and local factories working 24-hour shifts, though this explanation didn’t satisfy everyone who heard it.
Starting in spring 1991, residents near Taos, New Mexico, complained of a low-level rumbling noise that disrupted their sleep and daily lives. The sound got enough attention that serious resources were deployed to find its source. A team of researchers from Los Alamos National Laboratory, the University of New Mexico, and Sandia National Laboratories conducted an investigation. Despite having access to sophisticated equipment and expertise, they were unable to identify where the sound was coming from.
Windsor, Ontario, became another Hum hotspot starting around 2011. Residents began reporting a low droning vibration, sometimes loud enough to be genuinely irritating rather than just mysterious. One evening in 2012 saw 22,000 reports flooding into officials. That number alone tells the story. In a single evening, twenty-two thousand people felt compelled to report this sound. Researchers eventually traced it to a probable source: the sound appeared to be emanating from Zug Island, a heavily industrialized section of River Rouge on the Detroit River. Colin Novak of the University of Windsor led a research team that confirmed the Windsor hum was indeed a real acoustic phenomenon with a measurable frequency of approximately 35 hertz.
Only about 2 percent of people living in any given Hum-prone area can hear the sound, according to a 2003 study by acoustical consultant Geoff Leventhall of Surrey, England. This creates an additional layer of frustration for those who do hear it. Most of the people who hear The Hum fall into the 55 to 70 age range, though younger people report it too.
The descriptions stay remarkably consistent across different locations and different languages. Most people describe the sound as similar to a diesel engine idling nearby. Always just out of sight. Always just beyond reach. The Hum has driven virtually every person who hears it to some level of despair.
Katie Jacques of Leeds, England, gave the BBC an interview that captures the psychological toll. She called it a kind of torture. The sound is worst at night, she said, making it hard to fall asleep because of the throbbing in the background. The more you try to ignore it, the more present it becomes. Sleep deprivation compounds. Frustration builds. Life gets harder.
Glen MacPherson understands this experience personally. He’s a high school teacher in British Columbia who founded the World Hum Map and Database Project in 2012. The site gathers, documents and maps detailed information from people who can hear the Hum. MacPherson created this resource because he became one of the hearers himself. In 2012, living in Sechelt, he started hearing a droning sound at night. He initially assumed it was seaplanes taking off and landing from the nearby water. Seaplanes are common in coastal British Columbia. The explanation made sense. Except it kept going. Eventually, he realized this sound was not being caused by planes or any other conventional source he could identify.

The Search For Explanations

Investigators typically start with the obvious suspects when people report hearing The Hum. Industrial equipment usually tops the list. In one instance, Leventhall successfully traced a reported hum to a neighboring building’s central heating unit. Problem solved. Other suspected sources include high-pressure gas lines, electrical power lines, and wireless communication devices. All of these can produce low-frequency sounds under certain conditions.
The challenge is that identifying these sources requires the sound to be consistent, measurable, and traceable. Only in a few cases has a Hum been definitively linked to a mechanical or electrical source. The majority remain mysteries.
Some researchers speculate that The Hum could result from low-frequency electromagnetic radiation, audible only to certain people. This theory has backing. Verified cases exist in which individuals demonstrate particular sensitivities to signals outside the normal range of human hearing. Their auditory systems pick up frequencies that most people’s ears simply can’t process.
Environmental factors provide another category of explanation. Seismic activity can generate sounds, specifically through microseisms. These are very faint, low-frequency earth tremors that can be generated by the action of ocean waves. The ocean constantly pounds against the continental shelf. Under certain conditions, this creates vibrations that travel through rock and can be perceived as sound by some individuals.
David Baguley, head of audiology at Addenbrooke’s Hospital in Cambridge, offered an assessment in 2009 based on years of working with people who reported hearing The Hum. He believed people’s problems with the hum were based on something real in the physical world about one-third of the time. The other two-thirds stemmed from people focusing too keenly on innocuous background sounds that normally get filtered out by the brain. Once you notice these sounds, once they register as significant, they become impossible to ignore. The majority of cases remain unexplained despite investigation.
Baguley developed a theory about modern auditory sensitivity. He proposed that peoples’ hearing has become overly sensitive, possibly as an adaptation to our increasingly noisy world or as a side effect of constant sound exposure. Research at the University of Salford took a different approach, focusing on using psychology and relaxation techniques to minimize distress due to the hum. The goal wasn’t to eliminate the sound but to change the relationship between the hearer and what they were experiencing. Some people reported that this approach led to a quieting or even removal of the noise from their conscious perception.

Coastal Cannon Fire

Seneca Guns represent another category of unexplained coastal sounds. These are repeated booms reported in specific locations, most famously along North Carolina’s Outer Banks and around Lake Seneca in New York. People hear them on sunny, quiet days when there are no storms brewing and no obvious sources of explosions. The name comes from Lake Seneca, where 19th-century settlers thought they were hearing artillery salvos from some distant, unseen conflict.
The phenomenon appears worldwide under different names. In Japan, people call these sounds “uminari,” which translates to “the rumbling of the sea.” Dutch speakers use “mistpouffers.” Italians say “brontidi.” The names differ but the descriptions match. Loud, cannon-like sounds coming from the direction of water on otherwise peaceful days.
These coastal sounds share characteristics with what Santos residents describe. They occur near water. They sound like distant cannon fire or explosions. They happen on otherwise quiet days when conventional explanations don’t fit. The similarity suggests Santos might be experiencing a variation of this global phenomenon.
Explanations for Seneca Guns vary. Some researchers point to offshore microseismicity, which refers to small earthquakes or slips occurring under the continental shelf. These events might not register on standard seismic equipment but could generate sounds that travel through water and reach coastal areas. Other theories involve underwater landslides or methane bursts creating pressure pulses that manifest as booms when they reach the surface. Atmospheric ducting provides yet another possibility. Sound can travel in unusual ways when temperature inversions or other atmospheric conditions create channels that carry noise over long distances, including across water.
The term “skyquake” entered online usage around 2004 as a catch-all descriptor for booms that have no readily discernible source. Sharon Hill, who has studied these phenomena extensively, notes that skyquakes can result from atmospheric ducting of noise from man-made explosions or thunder traveling from far away. Under certain meteorological conditions, sounds behave in counterintuitive ways. They can travel through the air in a preferred path or bounce off layers in the atmosphere. This means sound from an event happening miles away might be loud and clear at a distant location while people in between hear nothing.
Single booms create particular investigative challenges. Unlike sustained sounds, they offer no opportunity for triangulation or measurement over time. Explosions are frequently one-off events whether they’re manufactured or accidental. The sound happens, echoes briefly, and fades. By the time anyone thinks to investigate, the moment has passed.
Low-frequency noises travel much farther than high-frequency sounds. This is basic physics. Weather conditions affect how far and in what direction sound travels, adding layers of complexity to any investigation. Temperature, humidity, wind, and atmospheric pressure all play roles in how sound propagates through air.
David Hill, Scientist Emeritus with the US Geological Survey, wrote a scientific review paper covering potential causes of mysterious booms. He noted that under proper circumstances, even sand dunes are capable of producing sounds. They can create a variety of low-level noises, and less commonly, loud booming sounds. The conditions have to be exactly right, but it happens. Nature contains more sound-generating mechanisms than most people realize.

Brazil’s History With The Unknown

Brazil has accumulated a long, well-documented history of UFO sightings and unexplained phenomena. The country is known internationally in UFO research circles, particularly for one event that stands out. The Varginha incident occurred on January 20, 1996. Researchers sometimes call it “Brazil’s Roswell,” comparing it to the famous American case. The Varginha incident involved numerous witnesses who claimed to have seen aliens over multiple days. Reports of UFO sightings accumulated. Then the Brazilian military apparently conducted some sort of investigation, though official details remain scarce.
In 1986, a series of UFO sightings occurred across southeastern Brazil that prompted an official military response. The sightings were widespread enough that several jet fighters were scrambled to intercept whatever was being reported. During these attempted interceptions, pilots reported observations that challenged conventional understanding of aircraft capabilities. They described objects capable of 90-degree turns and hypersonic flight. These weren’t civilians making vague reports. These were trained military pilots operating sophisticated aircraft, reporting phenomena they couldn’t explain.
May 12, 2020, brought unexplained lights to Magé, a city in Rio de Janeiro state. From around 10:40 PM until 2:00 AM, residents recorded videos showing several strange lights of different colors moving through the city’s sky. The footage spread across social media. People compared notes. The lights didn’t behave like aircraft, drones, or any other conventional explanation people could offer.
Santos itself appears in UFO records. At around 1 AM on May 16, 1994, a local man reported watching four round objects moving erratically above the city for around 30 minutes. He had time to observe them, to note their movements, to confirm they didn’t match anything in his experience.
March 6, 1982, brought one of the more remarkable mass sighting events. During a match of the 1982 Campeonato Brasileiro Série A between Operário-MS and CR Vasco da Gama, something appeared in the sky above the Morenão stadium. The stadium held an audience of more than 24,000 people that evening. Multiple witnesses reported seeing flying objects. The witnesses included some of the players on the field and the match referee, José de Assis Aragão. These were people whose attention should have been completely focused on the game, yet something in the sky was compelling enough to distract them.
The Brazilian National Archives began receiving documentation from the Brazilian Air Force regarding UFO investigations in 2008. The collection now gathers cases spanning from 1952 to 2016. In 2024 alone, the archives contain at least 26 reports of UFOs seen by pilots, air traffic controllers, and other witnesses who filed official reports with the Air Force Command. These aren’t internet rumors or unverifiable claims. These are formal reports in official government archives.

The Scientific Investigation

Santos has become the focus of serious scientific attention regarding underwater sound, though this research predates the recent mysterious breathing sounds. Since 2015, a comprehensive acoustic program called the Santos Basin Underwater Soundscape Monitoring Project has been underway. The state-owned company Petrobras runs the project in partnership with the Brazilian Navy. The scale and scope of the research is remarkable, providing unprecedented passive underwater acoustic measurements in the southwestern South Atlantic.
The project aims to quantify and assess hydroacoustic noise of anthropogenic origin throughout the large sedimentary basin extending from 23° S to 28° S on the southeastern Brazilian continental margin. This covers a massive area. The primary target is noise associated with oil and gas exploration and production activities, but the research captures all underwater sounds in the region.
Researchers use a variety of equipment and data acquisition methods. Multiple listening stations, both fixed and mobile, capture sounds at different depths and locations. The goal is creating a comprehensive metrological assessment of the underwater soundscape in the region. The measurements contribute to understanding the baseline soundscape and monitoring any increases in underwater noise in areas affected by growing oil and gas activities.
This existing infrastructure means Santos has better underwater acoustic monitoring than most coastal cities. If the mysterious breathing sound has an underwater component, the equipment should theoretically be capable of detecting and measuring it. Whether that data exists, and whether researchers have made connections between their monitoring and residents’ reports, remains unknown.
Underwater soundscape studies in Brazil have historically served two main purposes. Some have had site-specific classified military objectives. Others aimed to characterize the sound or behavior of specific marine species. The Santos Basin project represents something different: a comprehensive, ongoing effort to document the entire acoustic environment of a major coastal region.

No Answers Yet

Experts in natural phenomena and astronomy have weighed in on the green light Roberta photographed. They indicate various possible causes. Reflections can create unusual aerial phenomena under the right conditions. Drones equipped with lights have become common enough to generate regular reports of mysterious objects. Optical phenomena occur when light behaves in unexpected ways through atmosphere, ice crystals, or other media. Meteorological events can produce visual effects that observers struggle to categorize.
None of these explanations fully satisfies the observers who saw the light move toward Ilha das Palmas. The speed of movement, the color, the apparent correlation with the figure at the water’s edge, all these details create a picture that doesn’t quite fit standard explanations.
The Scottish Association for Marine Science offered an interesting hypothesis when investigating similar sounds in Hythe, Hampshire. They suggested that nocturnal humming could be produced by certain species of fish. Some fish species do generate sounds, using specialized organs or body parts to create clicks, grunts, or humming noises. However, the council in Hythe believed this explanation was unlikely for their specific case, since the fish species capable of producing such sounds are not commonly found in inshore waters of the UK. Whether similar fish exist in Brazilian coastal waters near Santos remains an open question.
The Port Authority maintains detailed, comprehensive records of all ship movements and mechanical operations. This isn’t a casual logging system. Port operations require precision documentation for safety, legal, and commercial reasons. Every ship movement gets recorded. Every mechanical operation gets logged. Their confirmation that nothing unusual occurred during the November 1st sound event carries weight. It eliminates the most obvious, prosaic explanation. Whatever residents heard, it wasn’t coming from normal port operations.
Residents continue to report the phenomena. The breathing sound from the sea persists during quiet early morning hours, maintaining its presence in the city’s daily life. The lights continue to appear in the sky, photographed and witnessed by multiple people who have no obvious reason to fabricate these encounters.
Santos heard something. The sound was real enough to wake people, to generate widespread social media discussion, to prompt official inquiries. Santos saw something. The photographs exist. The witnesses compare accounts. Nobody knows what either one was.

References

Moradora registra luz verde no céu em Santos, mesma região do barulho misterioso
Mistério em Santos: moradores ouvem barulhos estranhos no mar durante a madrugada
The Hum, a worldwide mystery sound explained
Mysterious hum driving people crazy around the world
The Hum – Wikipedia
The World Hum Map and Database Project
Cracking the mystery of the ‘Worldwide Hum’
Understanding the Mysterious Hum That Tortures a Select Few
‘The Hum’ Noise: Mystery Sound Is Invading Towns
How the Hum Works
Is “the Hum” a scientific fact or a mass delusion?
UFO sightings in Brazil – Wikipedia
Sao Paulo, Brazil: A Discreet UFO Hotspot
The Brazilian Santos basin underwater soundscape monitoring project
Santos: progress and beauty by the sea
Earthquake Booms & Seneca Guns – Cannon-Like Skyquakes
Mystery booms and skyquakes

NOTE: Some of this content may have been created with assistance from AI tools, but it has been reviewed, edited, narrated, produced, and approved by Darren Marlar, creator and host of Weird Darkness — who, despite popular conspiracy theories, is NOT an AI voice.