10 sons não identificados que os cientistas estão analisando seriamente

Nós, humanos, somos muito bons em reconhecer sons. Nossos ouvidos são suficientemente sensíveis para diferenciar variações no som equivalentes a menos de um bilionésimo da pressão atmosférica, e nossos cérebros têm a capacidade de identificar e memorizar padrões auditivos complexos [fontes: GSU , CNRS ]. Essa habilidade provavelmente evoluiu porque nossos ancestrais tinham uma chance melhor de sobrevivência se pudessem dizer a diferença entre, digamos, o assobio do vento e o silvo de um gato dente-de-sabre prestes a atacar.

Mas essa habilidade inata de classificar os ruídos pode ser parte do motivo pelo qual é tão perturbador ouvir um som que não conseguimos identificar. Também não ajuda nosso nível de ansiedade que as pessoas associam há muito tempo sons misteriosos a fenômenos paranormais , como poltergeists.

Graças ao avanço da ciência, porém, muitos sons antes classificados como "inexplicáveis" agora são identificáveis. Um exemplo é o "Bloop", um ruído misterioso que os pesquisadores registraram nas águas do Oceano Pacífico em 1997. A Administração Nacional Oceânica e Atmosférica (NOAA) certa vez classificou a origem do Bloop como "desconhecida". Mas nos últimos anos, os cientistas descobriram que o Bloop provavelmente foi causado pela quebra e fratura de icebergs, o que causa tremores chamados de icequakes [fontes: NOAA PMEL , Newitz ].

Outros sons permanecem um quebra-cabeça. Aqui estão 10 para os quais os cientistas ainda não chegaram a uma explicação conclusiva.

1. O Uau! Sinal
2. O Upsweep
3. O trompete
4. O caçador de Lincolnshire
5. UVB-76: AKA, 'A campainha'
6. Fenômenos de Voz Eletrônica (EVP)
7. O Incidente de Altura Máxima
8. Lanças Misteriosas
9. Sons estranhos do planeta Saturno
10. O Taos Hum

Em 1977, apenas alguns meses antes do lançamento de "Contatos Imediatos do Terceiro Grau", do diretor Steven Spielberg , cientistas da vida real detectaram o que pelo menos inicialmente acreditavam ser uma mensagem de rádio enviada por extraterrestres distantes [fonte: Kiger ].

No agora extinto observatório de radiotelescópio Big Ear da Ohio State University, que na época estava procurando por tais sinais, um voluntário chamado Jerry Ehman notou um sinal extremamente poderoso - 30 vezes mais alto que o ruído ambiente típico do espaço profundo - e extremamente perto de 1.420 megahertz, a frequência do hidrogênio . (Isto foi representado pelo "U" na impressão de frequências eletromagnéticas do telescópio. Ehman escaneava essas impressões todos os dias.) Mas o sinal durou apenas 72 segundos, e mais de 100 estudos subsequentes dessa mesma região do céu não conseguiram descobrir qualquer coisa incomum. Foi o Uau! sinal enviado por uma civilização distante com um transmissor extremamente poderoso, ou apenas alguma anomalia natural? Décadas depois, ainda não sabemos [fontes:Kiger ].

Os oceanos da Terra são uma cacofonia de ruídos muitas vezes bizarros, causados ​​por uma variedade de fontes, desde tremores vulcânicos a navios, até mamíferos aquáticos, como baleias jubarte [fonte: Bobbitt ]. Cientistas da Administração Nacional Oceânica e Atmosférica estudam esses sons há anos, com a ajuda de uma rede de escuta subaquática que usa hidrofones, que produzem sinais de tensão em uma faixa de frequências à medida que captam sons subaquáticos de qualquer direção [fonte: Fox ].

Um misterioso som inexplicável é o Upsweep , um conjunto de sons ascendentes de banda estreita, cada um com duração de vários segundos e detectado pela primeira vez por cientistas em 1991. O Upsweep parece ser sazonal e geralmente atinge seu pico na primavera e no outono, embora ninguém tem certeza porque. O nível da fonte é alto o suficiente para ser registrado em todo o Pacífico [fonte: PMEL ].

In the summer of 2013, a woman in British Columbia began hearing a loud, trumpet-like sound, and one morning she recorded it with her video camera and posted it to YouTube. While some questioned its authenticity, there have been other reports of a similar sound from Texas to Norway.

There are some variations: Sometimes the noise sounds more like the moan of an animal, while other manifestations resemble a low-pitched rumble, a whine or a thumping. Nobody has determined what it is, though University of Saskatchewan physics professor Jean Pierre St. Maurice has hypothesized that the noises may be from electromagnetic waves coming from aurora , natural light displays mostly seen in the Arctic and Antarctic skies [source: Huffington Post].

During the Cold War from the 1950s to the 1980s, shortwave radio enthusiasts across the world began noticing weird broadcasts that would often start with music or the sound of beeps, which would be followed by even more strangeness -- the voice of a woman counting in German, for example, or a child's voice reciting letters from the alphabet in English. Listeners gave them amusing names, such as "Nancy Adam Susan," "The Swedish Rhapsody" or "The Gong Station." Listeners assumed they were signals for secret messages to spies [source: Sorrel-Dejerine].

One of the strangest was "The Lincolnshire Poacher," which used a snippet of an English folk song of that name. After about 10 minutes of music, a female voice with an English accent would read what appeared to be a coded message. According to Dutch cryptology historian Dirk Rijmenants, the Lincolnshire Poacher appeared during the 1970s and aired daily until 2008, when it mysteriously disappeared. The common assumption is that it was some sort of communication between British intelligence and agents in the field, but there's never been any official confirmation, so it still qualifies as unidentified.

If you thought the Lincolnshire Poacher was weird, the story of UVB-76 is even weirder. According to Wired U.K. reporter Peter Savodnik, starting in the early 1980s, a mysterious radio tower north of Moscow transmitted a bizarre assortment of beeps, and then in 1992 switched to buzzing sounds that each lasted about a second and occurred between 21 and 34 times per minute. Once every few weeks, that routine would be interrupted briefly by a male voice reciting brief strings of numbers and words, usually Russian names such as Anna and Nikolai. The tones, amplitude and pitch of the buzzing shifted, and the intervals between it would vary as well. But every hour, on the hour, the station quickly would buzz twice.

Even more oddly, after years of daily broadcasts, the station briefly stopped sending out signals in June 2010 and again in August of that year. Then, toward the end of that month, UVB-76 suddenly underwent a startling metamorphosis, with thuds and shuffling sounds creeping into the broadcasts, frequent interruptions by snippets of "Dance of the Little Swans" from Tchaikovsky's "Swan Lake," and occasional recitations of cryptic messages such as "04 979 D-R-E-N-D-O-U-T" followed by long strings of numbers. Again, the assumption by shortwave buffs is that the station is transmitting messages to secret agents [source: Savodnik].

For decades, paranormal believers have been picking up stray voices on tape recordings, which some think come from dead people or extraterrestrials. As a website for paranormal enthusiasts explains, picking up electronic voice phenomena, or EVP, often requires a person to listen to the recording with headphones and work hard to pick the voices out from the background noise, and sometimes a recording will have to be played in reverse for the message to appear [source: ATC]. (A similar technique was used by teenage Beatles conspiracy theorists in the late '60s, when they played "Strawberry Fields Forever" backward in an effort to hear what sounded to some like "I buried Paul.")

But not everybody believes EVP is truly paranormal. The Skeptic's Dictionary, for example, offers effects such as interference from a local CB operator , and various sorts of naturally occurring electronic distortion as possible explanations.

This one is unexplained, in that nobody knows who did it or how they did it. On Nov. 22, 1989, a hacker managed to take over the frequencies of two Chicago-area TV stations. The first time, during a CBS newscast, technicians shut it down in 30 seconds. But the second attack, against a public TV station, lasted well over a minute. The PBS drama cut out and a man in a Max Headroom mask appeared, broadcasting a cryptic audio message, with lines like "your love is fading" and a hummed snippet of the theme song from the cartoon "Clutch Cargo" [source: Finley].

An Federal Communications Commission investigator said that whoever did it could have used simple gear, but had to have a sophisticated knowledge of broadcasting technology.

Back in 1850, James Fenimore Cooper wrote a short story called "The Lake Gun," which recounted how people sometimes heard a loud, inexplicable explosive sound in the woods around Seneca Lake in New York. Cooper described it as "a sound resembling the explosion of a heavy piece of artillery that can be accounted for by none of the known laws of nature. The report is deep, hollow, distant, and imposing."

Since Cooper's time, people in various parts of the U.S. have been startled by similar booms -- though, when they get over their shock, they discovered that nothing appears to have been blown up, and no supersonic aircraft have been flying nearby. In 2012, for example, residents of Alabama, Georgia and Wisconsin all experienced shaking followed by loud booms. Scientists have speculated that the booms are probably caused by shallow earthquakes that are too small to be reported, yet large enough to be felt by people nearby. Or else, they may be sonic booms from planes traveling faster than the speed of sound. But nobody knows for sure [sources: USGS, Daniel].

Back in 2009, the Cassini spacecraft picked up Saturn Kilometric Radiation, or SKRs, natural radio signals being emitted by Saturn . What was bizarre was the pattern of the sounds, which they couldn't explain -- it's actually two signals, one from the planet's north pole and the other from the south pole, in an out-of-sync duet [source: Space.com].

While these sounds normally would be inaudible to human ears , scientists have altered them to create really spooky-sounding recordings. (They sound a bit like bursts from an air raid siren.) As University of Iowa scientist Don Gurnett, who headed Cassini's instrument team, told Space.com, "These data just go to show how weird Saturn is."

Taos, New Mexico isn't the only place where a bizarre ambient hum is heard, but it's probably the most famous spot for the mysterious droning, so much that it's mentioned in travel guidebooks about the area. The Taos Hum reportedly is heard by only 2 percent of the local population and been described as a sound similar to the low rumble of a diesel truck's engine [source: Eisenberg].

People who noticed it are bothered to varying degrees, with some experiencing a mild feeling of irritation, while others report sleep disturbances, dizziness and nosebleeds. Conspiracy theorists suggest that it's caused by some sort of secret military communications system used to contact submarines , or a clandestine weapons testing program.

However, scientists think it may be caused by low frequency waves that originate in the atmosphere or else by vibrations from deep within Earth. A third hypothesis is that some people are extraordinarily sensitive to certain electromagnetic frequencies, and that the hum is caused by devices such as cell phones. But again, nobody really knows for sure [sources: Strange Sounds, Eisenberg].

Author's Note: 10 Unidentified Sounds That Scientists Are Seriously Looking Into

I can't say that I've experienced any of the unexplained sounds described in this article—I was in Taos once during the mid-1980s, for example, and the only odd phenomenon that I noticed was a local artist who wore cowboy boots that he'd apparently spray-painted fluorescent orange. When I started working in downtown Baltimore a few years later, I remember that on one of my first afternoons on the job, I was startled by the loud, eerie wail of a siren. No one else in the office seemed to notice it. I eventually discovered that it was the weekly test of an emergency alert system, and sounded at 1 p.m. each Monday. In time, I became accustomed to it as well.

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