The sound is the 1st known energy of nature and universe.it was known as "sruthi"

There are 1432 sruthi in nature as identified by ancient monks . this identification have a history as same long as the living  creaters with in this planet. Sruthy later known as manthras and music was formed from manthra. What Is a Mantra and How Does It Work

A saying from the Vedas claims that "Speech is the essence of humanity." All of what humanity thinks and ultimately becomes is determined by the expression of ideas and actions through speech and its derivative, writing. Everything, the Vedas maintain, comes into being through speech. Ideas remain unactualized until they are created through the power of speech. Similarly, The New Testament, Gospel of John, starts "In the beginning was The Word. And the Word was with God and the Word was God…" In mainstream Vedic practices, most Buddhist techniques and classical Hinduism, mantra is viewed as a necessity for spiritual advancement and high attainment. In The Kalachakra Tantra, by the Dalai Lama and Jeffrey Hopkins, the Dalai Lama states, "Therefore, without depending upon mantra…Buddhahood cannot be attained." Clearly, there is a reason why such widely divergent sources of religious wisdom as the Vedas, the New Testament and the Dalai Lama speak in common ideas. Here are some important ideas about mantra which will enable you to begin a practical understanding of what mantra is and what it can do.  When you chant a mantra, you merge with the sound vibration and become at one with the energy wavelength of the object of your mantra. Mantra chanting makes you at one with everyone, everywhere who is chanting that mantra and with everyone who has ever chanted the mantra. All the saints who have ever reached enlightenment through the technique of chanting that mantra connect with you as you connect with the vibration of the mantra. You merge with their essence which has been purified and is holy and you become pure and holy because that divine level of existence vibrates only with holiness, peace, and bliss. By chanting a mantra, your cells, molecules, atoms, and sub-atomic particles all vibrate in the same wavelength as the mantra. Once attuned with this vibration you connect with everything resonating on that plane of existence. It's like tuning a radio. At first you may get static, but once you are in the right frequency your reception is perfect. Om is the universal sound. It is within every word and within everything. So when you chant Om, you merge with all energy and all forms, from the sub-atomic to the universal, from the most gross to the most divine. And when you are tuned in perfectly, you will receive holy frequencies clearly and merge and emerge at one with the source of all and live happily ever after. Many meditation teachers suggest that it is necessary to understand every intellectual aspect of the meaning of the mantra that is being practiced, but just as many others feel that the intellect may tend to confuse and hold back spiritual progress. What both types of teachers agree on is that mantras have the potential to take practitioners to the level of consciousness that transcends the limitations of the mind by a billion-fold. There is an ancient tale that very well shows that true devotion and complete absorption are the key: Once upon a time in a land far away lived a poor uneducated, mentally challenged man who tended a herd of cows for his master. He happened upon a meditation teacher and was very taken with his calm, loving, gentle and happy nature. He decided he wanted to know that experience first hand. And so he went to the teacher and begged him to teach him a way to achieve the inner peace that radiated so obviously from the teacher. The teacher accepted him as his student but quickly found that the man couldn't understand any of the philosophical points he was making and as a matter of fact couldn't even remember the mantra Om when he tried to teach it to him. The teacher lovingly said, "My oh my, you don't seem to know anything at all, can't be taught, and can't remember anything. You are devoted and sincere in your desire to gain happiness though, so I will try to help you. My son, what do you know?" The man said, "Oh great teacher, the only thing I know is cows. All my life I've spent caring for cows, making sure they graze, are milked, and are kept clean. Yes, for me, everything is cows." "Well, that's alright," said the teacher, "then you know what sound the cows make." "Oh yes," said the man, "they say moo." "Very well then," said the teacher, "for you, moo will be your mantra. All you have to do is say moo continually and you will reach freedom from suffering and know real bliss." So the man chanted moo, moo, moo when he took the cows out to graze and he chanted moo, moo, moo when he milked them, and he chanted moo, moo, moo when he cleaned them. He chanted moo all the time and very soon merged with that vibration, which is Om backward, and reached the highest heights of joyous understanding and lived happily ever after. From this story, we learn that it is virtually impossible to chant Om "wrong". It is, after all, an insentient sound. But the giver of this sound to the universe knows the intention and devotion of the practitioner and that is by what we will be rewarded. It is said that one minute of sincere chanting is superior to a thousand hours of mere sounding of the words. A parrot can be taught to recite a mantra but this will be just mere vibrations in the air. It is the love and worship behind the sound that counts. Technically though, there is a "correct" way to chant Om. It is made up of three letters: A, U, M. These contain all the sounds there are. The A is guttural and comes from the throat. It is pronounced without any part of the tongue or palate in contact. The U sound comes from the middle of the sounding board, the palate. In Sanskrit, the A and U join together to become O. The O sound is vibrated from the navel/ solar plexus area and sent up to the sternum to the voice region, the lips, where the M sound is prolonged and vibrated up to the crown of the head. This vibrating M is felt in every cell of the body and is beamed out lovingly, soothingly, powerfully, to everything, everyone, everywhere. Intellectually and metaphysically, A stands for the physical world perceptible to the senses, the material world. U represents the astral and dream planes, heaven and hell. M is the unknown, deep sleep, and that which is unfathomable to the intellect. Thus Om contains the entire spectrum of sound, words, worlds, and concepts. Om represents the source of all light, love, and wisdom. There are three ways to do mantras - aloud, silently but while mouthing or humming the mantra, and completely silently within oneself. When done aloud and particularly when done with others, the sound of Om is energizing, calming, and healing. Although it is often encouraged to do your mantra all the time, it would certainly be questionable to consider chanting Om aloud in the middle of a board meeting. Similarly, it may be preferable to do Om silently just by moving your lips if you are in a movie theater. Chanting Om completely silently is considered the most potent method because it is not dependent on having a human voice box, or lips, or facial muscles, all of which are temporary manifestations compared to the billions of years you will be fully at one with Om. It is advantageous to spiritual development to consider the theological, philosophical and mystical aspects of Om while chanting with your physical eyes closed, looking through the third eye, and paying attention to your breath. This may seem complex and complicated, but once in synch, it happens naturally as Om reveals itself, your Real Self, to you

Mantras are energy-based sounds.

Saying any word produces an actual physical vibration. Over time, if we know what the effect of that vibration is, then the word may come to have meaning associated with the effect of saying that vibration or word. This is one level of energy basis for words. Another level is intent. If the actual physical vibration is coupled with a mental intention, the vibration then contains an additional mental component which influences the result of saying it. The sound is the carrier wave and the intent is overlaid upon the wave form, just as a colored gel influences the appearance and effect of a white light. In either instance, the word is based upon energy. Nowhere is this idea more true than for Sanskrit mantra. For although there is a general meaning which comes to be associated with mantras, the only lasting definition is the result or effect of saying the mantra.

The human consciousness is really a collection of states of consciousness which distributively exist throughout the physical and subtle bodies. Each organ has a primitive consciousness of its own. That primitive consciousness allows it to perform functions specific to it. Then come the various systems. The cardio-vascular system, the reproductive system and other systems have various organs or body parts working at slightly different stages of a single process. Like the organs, there is a primitive consciousness also associated with each system. And these are just within the physical body. Similar functions and states of consciousness exist within the subtle body as well. So individual organ consciousness is overlaid by system consciousness, overlaid again by subtle body counterparts and consciousness, and so ad infinitum. The ego with its self-defined "I" ness assumes a pre-eminent state among the subtle din of random, semi-conscious thoughts which pulse through our organism. And of course, our organism can "pick up" the vibration of other organisms nearby. The result is that there are myriad vibrations riding in and through the subconscious mind at any given time. Mantras start a powerful vibration which corresponds to both a specific spiritual energy frequency and a state of consciousness in seed form. Over time, the mantra process begins to override all of the other smaller vibrations, which eventually become absorbed by the mantra. After a length of time which varies from individual to individual, the great wave of the mantra stills all other vibrations. Ultimately, the mantra produces a state where the organism vibrates at the rate completely in tune with the energy and spiritual state represented by and contained within the mantra. At this point, a change of state occurs in the organism. The organism becomes subtly different. Just as a laser is light which is coherent in a new way, the person who becomes one with the state produced by the mantra is also coherent in a way which did not exist prior to the conscious undertaking of repetition of the mantra.

They are formidable. They are ancient. They work. The word "mantra" is derived from two Sanskrit words. The first is "manas" or "mind," which provides the "man" syllable. The second syllable is drawn from the Sanskrit word "trai" meaning to "protect" or to "free from." Therefore, the word mantra in its most literal sense means "to free from the mind." Mantra is, at its core, a tool used by the mind which eventually frees one from the vagaries of the mind. But the journey from mantra to freedom is a wondrous one. The mind expands, deepens and widens and eventually dips into the essence of cosmic existence. On its journey, the mind comes to understand much about the essence of the vibration of things. And knowledge, as we all know, is power. In the case of mantra, this power is tangible and wieldable.

Mantras have close, approximate one-to-one direct language-based translation. If we warn a young child that it should not touch a hot stove, we try to explain that it will burn the child. However, language is insufficient to convey the experience. Only the act of touching the stove and being burned will adequately define the words "hot" and "burn" in the context of "stove." Essentially, there is no real direct translation of the experience of being burned. Similarly, there is no word which is the exact equivalent of the experience of sticking one's finger into an electrical socket. When we stick our hand into the socket, only then do we have a context for the word "shock." But shock is really a definition of the result of the action of sticking our hand into the socket. It is the same with mantras. The only true definition is the experience which it ultimately creates in the sayer. Over thousands of years, many sayers have had common experiences and passed them on to the next generation. Through this tradition, a context of experiential definition has been created. Definitions of mantras are oriented toward either the results of repeating the mantra or of the intentions of the original framers and testers of the mantra. In Sanskrit, sounds which have no direct translation but which contain great power which can be "grown" from it are called "seed mantras." Seed in Sanskrit is called "Bijam" in the singular and "Bija" in the plural form. Please refer to the pronunciation guide on page 126 for more information on pronunciation of mantras. Let's take an example. The mantra "Shrim" or Shreem is the seed sound for the principle of abundance (Lakshmi, in the Hindu Pantheon.) If one says "shrim" a hundred times, a certain increase in the potentiality of the sayer to accumulate abundance is achieved. If one says "shrim" a thousand times or a million, the result is correspondingly greater. But abundance can take many forms. There is prosperity, to be sure, but there is also peace as abundance, health as wealth, friends as wealth, enough food to eat as wealth, and a host of other kinds and types of abundance which may vary from individual to individual and culture to culture. It is at this point that the intention of the sayer begins to influence the degree of the kind of capacity for accumulating wealth which may accrue.

1.        Mantras have been tested and/or verified by their original framers or users.

Each mantra is associated with an actual sage or historical person who once lived. Although the oral tradition predates written speech by centuries, those earliest oral records annotated on palm leaves discussed earlier clearly designate a specific sage as the "seer" of the mantra. This means that the mantra was probably arrived at through some form of meditation or intuition and subsequently tested by the person who first encountered it.

1.        Sanskrit mantras are composed of letters which correspond to certain petals or spokes of chakras in the subtle body.

As discussed in Chapter 2, there is a direct relationship between the mantra sound, either vocalized or subvocalized, and the chakras located throughout the body.

1.        Mantras are energy which can be likened to fire.

You can use fire either to cook your lunch or to burn down the forest. It is the same fire. Similarly, mantra can bring a positive and beneficial result, or it can produce an energy meltdown when misused or practiced without some guidance. There are certain mantra formulas which are so exact, so specific and so powerful that they must be learned and practiced under careful supervision by a qualified teacher. Fortunately, most of the mantras widely used in the West and certainly those contained in this volume are perfectly safe to use on a daily basis, even with some intensity.

1.        Mantra energizes prana.

"Prana" is a Sanskrit term for a form of life energy which can be transferred from individual to individual. Prana may or may not produce an instant dramatic effect upon transfer. There can be heat or coolness as a result of the transfer. Some healers operate through transfer of prana. A massage therapist can transfer prana with beneficial effect. Even self-healing can be accomplished by concentrating prana in certain organs, the result of which can be a clearing of the difficulty or condition. For instance, by saying a certain mantra while visualizing an internal organ bathed in light, the specific power of the mantra can become concentrated there with great beneficial effect.

1.        Mantras eventually quiet the mind.

At a deep level, subconscious mind is a collective consciousness of all the forms of primitive consciousnesses which exist throughout the physical and subtle bodies. The dedicated use of mantra can dig into subconscious crystallized thoughts stored in the organs and glands and transform these bodily parts into repositories of peace. 

As per the modern scientific aspect, sound can defined as follows.

Sound is a longitudinal, mechanical wave.Sound can travel through any medium, but it cannot travel through a vacuum. There is no sound in outer space.Sound is a variation in pressure. A region of increased pressure on a sound wave is called a compression (or condensation). A region of decreased pressure on a sound wave is called a rarefaction (or dilation).The sources of sound

"        vibrating solids

"        rapid expansion or compression (explosions and implositons)

"        Smooth (laminar) air flow around blunt obstacles may result in the formation of vorticies (the plural of vortex) that snap off or shed with a characteristic frequency. This process is called vortex shedding and is another means by which sound waves are formed. This is how a whistle or flute produces sound. Aslo the aeolian harp effect of singing power lines and fluttering venetian blinds.

What are the different characteristics of a wave? What are the things that can be measured about waves? Amplitude, frequency (and period), wavelength, speed, and maybe phase. Deal with each one in that order.

amplitude, intensity, loudness, volume

Amplitude goes with intensity, loudness, or volume. That's the basic idea.

frequency, pitch, tone

"        Typical sounds produced by human speech have frequencies on the order of 100 to 1000 Hz.

"        The peak sensitivity of human hearing is around 4000 Hz.

The speed of sound depends upon the type of medium and its state. It is generally affected by two things: elasticity and inertia. Elasticity

gases        liquids        solids

               

? = CP/CV

k = Boltzmann's constant

T = Kelvin temperature

m = molecular mass

P = pressure

B = bulk modulus

? = density        B = bulk modulus

? = density        Y = Young's modulus

? = density

Speed of Sound in Various Materials

solids        v (m/s)                liquids        v (m/s)

aluminum        6420                alcohol, ethyl        1207

beryllium        12,890                alcohol, methyl        1103

brass        4700                mercury        1450

brick        3650                water, distilled        1497

copper        4760                water, sea        1531

cork        500                        

glass, crown        5100                        

glass, flint        3980                gases (STP)        v (m/s)

glass, pyrex        5640                air, 000 °C        331

gold        3240                air, 020 °C        343

granite        5950                argon        319

iron        5950                carbon dioxide        259

lead        2160                helium        965

lucite        2680                hydrogen (H2)        1284

marble        3810                neon        435

rubber, butyl        1830                nitrogen        334

rubber, vulcanized        54                nitrous oxide        263

silver        3650                oxygen (O2)        316

steel, mild        5960                water vapor, 134 °C        494

steel, stainless        5790                        

titanium        6070                biological materials        v (m/s)

wood, ash        4670                soft tissues        1540

wood, elm        4120                        

wood, maple        4110                        

wood, oak        3850                        

Sources: Unknown, but probably an old version of the CRC

Acoustic Thermometry of Ocean Climates (ATOC)

"        in water, sounds below 1 kHz travel much farther than higher frequencies

"        "shipping noise is loudest in the 30 to 200 Hz range [lowest piano note to middle of cello]"

"        "blue and fin wales are the loudest sound in the 17 to 30 Hz range"

"        "In pre-industrial times, the low frequency range of 15 to 300 Hz in which most of the baleen whales sings was the quietest part of the sound spectrum, nestled between the subsonic ramblings of earthquakes and the higher pitched rattle of wind, waves and rain." Bob Holmes. "Noises Off." New Scientist. 1 March 1997: 30-33.

echoesscraps

"        As with any wave the speed of sound depends on the medium in which it is propagating.

"        Sound generally travels faster in solids and liquids than in gases.

"        The speed of sound is faster in materials that have some stiffness like steel and slower in softer materials like rubber.

"        Factors Which Affect the Speed of Sound in Air.

"        The speed of sound in air is approximately 330 m/s (about 1,200 kph or 700 mph).

"        The speed of sound in air is nearly the same for all frequencies and amplitudes.

"        It increases with temperature.

"        Determining the Distance to a Lightning Bolt: Sound waves take approximately 5 seconds to travel 1 mile. Using this information, it is possible to measure one's distance from a lightning bolt. Begin counting immediately after you see the flash. Every five seconds counted is roughly equivalent to one mile of distance.

The frequency of a sound wave is called it pitch. High frequency sounds are said to be "high pitched" or just "high"; low frequency sounds are said to be "low pitched" or just "low". Humans are generally capable of hearing sounds between 20 Hz and 20 kHz (although I can't hear sounds above 13 kHz). Sounds with frequencies above the range of human hearing are called ultrasound. Sounds with frequencies below the range of human hearing are called infrasound.

Frequency of Selected Sounds [expand this table]

f (MHz)        device, event, phenomena, process

1 - 20        medical ultrasound

       

f (kHz)        device, event, phenomena, process

25 - 80        bat sonar clicks

40 - 50        ultrasonic cleaning

32.768        quartz timing crystal

18 - 20        upper limit of human hearing

4 - 5        field cricket (Teleogryllus oceanicus)

2 - 5        maximum sensitivity of the human hear

       

f (Hz)        device, event, phenomena, process

300 - 3000        voice frequency (VF), important for understanding speech

2048        C7 scientific scale, highest note of a soprano singer (approximate)

440        A4 american standard pitch, tv test pattern tone

435        A4 international pitch

426.67        A4 scientific scale

261.63        C4 american standard pitch

258.65        C4 international pitch

256        C4 scientific scale, typical fundamental frequency for female vocal cords

128        C3 scientific scale, typical fundamental frequency for male vocal cords

64        C2 scientific scale, lowest note of a bass singer (approximate)

90        ruby-throated hummingbird in flight

60        alternating current hum (US and Japan)

50        alternating current hum (Europe)

8 - 20        lower limit of human hearing

17 - 30        blue and fin wales are the loudest marine sound in this range

1 - 5        tornadoes

"        ultrasound

o        ?

"        infrasound

o        Elephants, whales, hippos, rhinoceros, giraffe, okapi, and alligator are just a few examples of animals that create infrasound.

o        Some migratory birds are able to hear the infrasonic sounds produced when ocean waves break. This allows them to orient themselves with coastlines.

"        bat

o        bats use ultrasonic frequencies of around 100,000 Hz to navigate

"        dolphin

o        ?

"        whale

o        ?

"        dog

o        Dogs can hear sound as high as 40,000 Hz.

"        cat

o        Cat's hearing range between 100 and 60,000 Hz

"        mice and rats

o        Mice can hear frequencies between 1,000 and 100,000 Hz.

o        Rat has hearing range between 1,000 and 90,000 Hz.

"        elephant

o        Elephant's hearing range between 1 and 20,000 Hz.

o        An elephant is capable of hearing sound waves well below our the human hearing limitation (approximately 30 Hertz). Typically, an elephant's numerous different rumbles will span between 14 and 35 Hertz. The far reaching use of high pressure infrasound opens the elephant's spatial experience far beyond our limited capabilities.

o        Silent Thunder, Katy Payne

"        rhinoceros

o        Rhinoceroses use infrasonic waves of about 5 Hz to signal to each other

"        pigeon

o        Pigeon can detect sounds as low as 0.1 Hz.

o        Mel Kreithen, Cornell University

"        insects

o        Grasshopper can hear up to 50,000 Hz.

o        Noctuid moth has a hearing range between 1,000 and 240,000 Hz.

"        miscellaneous

o        Drum Fish: Collects underwater sound vibrations with an air bladder. The signals are then send from the air bladder to the "weberian apparatus" in the middle ear and then to the inner ear. Hair cells in the inner ear respond to the vibration and transmit sound information to the fish brain.

o        Snakes have no external ears. Therefore, they do not hear the music of a "snake charmer". Instead, they are probably responding to the movements of the snake charmer and the flute. However, sound waves may travel through bones in their heads to the middle ear.

ultrasound

"        animal echolocation

o        microchiropterans a.k.a. microbats: carnivorous bats (not fruit bats or flying foxes)

o        cetaceans: dolphins, porpoises, orcas, whales

o        two bird species: swiftlets and oilbirds

o        some visually impared humans have learned this technique

"        sonar (an acronym for sound navigation and ranging) including

o        bathymetry

o        echo sounding

o        fish finders

"        medical ultrasonography (the images generated are called sonograms).

       frequency

(MHz)        power

(W)        intensity

(W/cm2)        pulse

duration

imaging, echo        1 - 20        0.05        1.75        0.2 - 1 ?s

imaging, doppler        1 - 20        0.15        15.7        0.3 - 10 ?s

physiotherapy        0.5 - 3        < 3        2.5        continuous

surgery        0.5 - 10        ~ 200        1,500        1 - 16 s

Source: Physics Today (December 2001)

"        avalanches: location, depth, duration

"        meteors: altitude, direction, type, size, location

"        ocean waves: storms at sea, magnitude, spectra

"        severe weather: location, intensity

"        tornadoes:detection, location, warning, core radius, funnel shape, precursors

"        turbulence: aircraft avoidance, altitude, strength, extent

"        earthquakes: precursors, seismic-acoustic coupling

"        volcanoes: location, intensity

"                 locating the source of sound Phase differences are one way we localize sounds. Only effective for wavelengths greater than 2 head diameters (ear-to-ear distances). a.k.a. Interaural Time Difference (ITD) Sound waves diffract easily at wavelengths larger than the diameter of the human head (around 500 Hz wavelength equals 69 cm). At higher frequencies the head casts a "shadow". Sounds in one ear will be louder than the other. a.k.a. Interaural Level difference (ILD) "         The human ear can distinguish some … 1400 different pitches  An understanding of sound is reinsting about forcasting of nature using sound. A most popular discussion was over after the Tsunami wave hits.  Sixth Sense?There were many stories after the December 26th 2004 tsunami of animals vacating the danger areas for higher ground hours before the deadly 'Harbour Wave' struck with such devasting effect.Flocks of birds, elephants, buffalo, antilopes etc. all flew and stampeded for higher and safer ground. Dogs refused to go for their run on the beach. Hares and rabbits had disapeared. In the aftermath of the tsunami's destruction, survivers were amazed at how few dead animals there were amonst the debris. In some parts not a single dead animal was found! All this was in areas where human fatalities were numerous and where cars and fishing boats had been flung into tree tops.There are no definate answers to this phenomenon but as you would expect, many theories. One theory is that animals have "sixth sense" although met with great sceptisism by scientists. There is thought that elephants have extra senses in their feet that can sense vibrations and even recognise different types of vibration. There is of course the fact that animals in general can hear frequencies that humans cannot. Animals also pick up on natural signs developed over thousands of years and this may give them alert signals. Humans are distracted by many material objects that have no interest whatsoever to the animal kingdom. Birds in particular are constantly adjusting to environmental changes, and perhaps their distress signals alert other creatures. Elephants are known to lay their trunks on the ground when an airplane or truck generates large seismic noise as if to feel it.The truth is that nobody knows for certain. But the fact is that, to a very great extent, animals escaped the 2004 tsunami.Wise Elephants.In Khao Lak, 50 miles north of Phuket along Thailand's western coast, a dozen elephants giving tourists rides began trumpeting hours before the tsunami struck the shore lines.About the time the 9.0-magnitude quake fractured the ocean floor. An hour before the wall of waves slammed the resort area, the elephants reportedly again grew agitated and began trumpeting in a distressed manner. Just before disaster struck, they fled for higher ground - some breaking their chains to flee. Flamingos that breed this time of year at Point Calimere sanctuary on India's southern coast left for safer forests well before the tsunami hit. One herd of elephants reportedly cleared a path in Banda Aceh, in order to make their way to higher ground. Sensitive to ground vibrations, elephants may have detected the undersea quake long before the tsunami hit. At the hard-hit Yala National Park in Sri Lanka, stunned wildlife officials reported that hundreds of elephants, leopards, tigers, wild boar, deer, water buffalo, monkeys and smaller mammals and reptiles had escaped unscathed. And while large turtles have been found dead in the debris along the shore of Indonesia's devastated Aceh province, the tsunami's impact on wildlife was "limited," said Frank Momberg, coordinator for emergency response in Aceh for the conservation group Fauna & Flora International.Tales of animals behaving strangely before the quake and of wildlife escaping to safety abounded in the wake of the tsunami, raising questions about what these members of the animal kingdom knew that humans didn't - and what, if anything, can be learned from it? Seismologists have sophisticated instruments that can measure quake factors during and after the fact, but experts admit no one can predict exactly when one will happen. Some scientists say certain animals have a kind of sensory hard-wiring that can detect earthquakes ahead of time, which one day might be replicated in man-made instruments.Reports of animals' "sixth sense" in detecting hurricanes, earthquakes, tsunamis and volcanic eruptions long before the earth starts shaking go back centuries. Rats racing from buildings, sparrows taking flight in flocks, dogs howling incessantly: It's an impressive track record, though anecdotal. After the 2004 tsunami, a Danish man staying in Ao Sane Beach, north of Phuket, wrote on a Danish Web site: "Dogs are smarter than all of us. . . . They started running away up to the hilltops long before we even realized what was coming."Looking for proof.Scientists are shy on a subject that, for obvious reasons, is difficult to replicate in a laboratory.There are always explanations and theories that mitigate the mystery of the anecdotes. In the case of this tsunami, says Ken Grant, project coordinator at the Humane Society International Asia office in Bali, Indonesia, a lot of animals escaped simply because they tend to live inland in the forest. Nevertheless, some scientists are looking for explanations of why some species behave strangely before natural catastrophes, by correlating the animals' sensory abilities with microscopic and invisible sensory stimuli."I don't know if I'd call this a sixth sense so much as a better sense," Grant says. "Most animals know that when the ground starts to shake something is wrong."Small Changes, Big Hints.Animals' sensory physiology - super-sensitive to sound, temperature, touch, vibration, electrostatic and chemical activity and magnetic fields - gives them a head start in the days and hours before natural calamities. "It appears a lot of animals have sensory organs that detect these micro-tremors and micro-changes that we cannot possibly monitor," says George Pararas-Carayannis, a former University of Hawaii oceanographer and geophysicist who leads the Tsunami Society."It's a sensitivity that we humans don't have. But animals through millions of years of evolution have developed it, and that's how they have been able to survive as a species. It is run or perish," says Pararas-Carayannis, author of the 2001 book "The Big One: The Next Great California Earthquake - Why, Where, and When It Will Happen." Do Indigenous People Sense Disaster?Indigenous peoples on some of the Indian Oceans remotest islands also faired well in surviving the tsunami. There was great fear that many would have been totally wiped out by the destructive wave. But in many cases the opposite was true. The instints and knowledge of nature of the tribes had sent many fleeing for the safety of the forests and higher ground.As one of the first Coast Guard helicopters with relief supplies for the tsunami victims slowed over the Indian Andaman and Nicobar islands to assess the damage, a lone tribesman sent a message from below: leave us alone. The lone Sentinelese man stood naked on the beach and shot a bow-strung arrow at the helicopter.The Sentinelese are one of five indigenous tribes on the Indian archipelago, and one of perhaps hundreds affected by the massive waves of last month's tsunami. The tribes' stories are vignettes of survival amidst massive destruction. In some cases, the disaster foraged ties to urban neighbors, but in others it highlighted the tribespeople's unique intuitive ties to nature that urban dwellers seem to lack.As the tsunami's death toll topped around a quarter of a million peole, just one of the 200 Moken living on Thailand's South Surin Island perished in the tsunami, and the ancestors of an ancient South Indian island tribe all survived when their king instructed them to rush up nearby mountains. 

A sound wave which travels through a medium by means of particle-to-particle interaction. As one particle becomes disturbed, it exerts a force on the next adjacent particle, thus disturbing that particle from rest and transporting the energy through the medium. Like any wave, the speed of sound refers to how fast the disturbance is passed from particle to particle. While wave length refers to the number of vibrations which an individual particle makes per unit of time, speed refers to the distance which the disturbance travels per unit of time. Always be cautious to distinguish between the two often confused quantities of speed (how fast…) and frequency (how often…).Since the speed of a wave is defined as the distance which a point on a wave (such as a compression or a rarefaction) travels per unit of time, it is often expressed in units of meters/second (abbreviated m/s). In equation form, this is

speed = distance/time

The faster a sound wave travels, the more distance it will cover in the same period of time. If a sound wave is observed to travel a distance of 700 meters in 2 seconds, then the speed of the wave would be 350 m/s. A slower wave would cover less distance - perhaps 660 meters - in the same time period of 2 seconds and thus have a speed of 330 m/s. Faster waves cover more distance in the same period of time. Factors Affecting Wave SpeedThe speed of any wave is depends with which the medium through which the wave is traveling. Typically there are two essential types of properties which affect wave speed - inertial properties and elastic properties. Elastic properties are those properties related to the tendency of a material to maintain its shape and not deform whenever a force or stress is applied to it. A material such as steel will experience a very small deformation of shape (and dimension) when a stress is applied to it. Steel is a rigid material with a high elasticity. On the other hand, a material such as a rubber band is highly flexible; when a force is applied to stretch the rubber band, it deforms or changes its shape readily. A small stress on the rubber band causes a large deformation. Steel is considered to be a stiff or rigid material, whereas a rubber band is considered a flexible material. At the particle level, a stiff or rigid material is characterized by atoms and/or molecules with strong attractions for each other. When a force is applied in an attempt to stretch or deform the material, its strong particle interactions prevent this deformation and help the material maintain its shape. Rigid materials such as steel are considered to have a high elasticity. (Elastic modulus is the technical term). The phase of matter has a tremendous impact upon the elastic properties of the medium. In general, solids have the strongest interactions between particles, followed by liquids and then gases. For this reason, longitudinal sound waves travel faster in solids than they do in liquids than they do in gases. Even though the inertial factor may favor gases, the elastic factor has a greater influence on the speed (v) of a wave, thus yielding this general pattern:vsolids > vliquids > vgasesInertial properties are those properties related to the material's tendency to be sluggish to changes in it's state of motion. The density of a medium is an example of an inertial property. The greater the inertia (i.e., mass density) of individual particles of the medium, the less responsive they will be to the interactions between neighboring particles and the slower that the wave will be. As stated above, sound waves travel faster in solids than they do in liquids than they do in gases. However, within a single phase of matter, the inertial property of density tends to be the property which has a greatest impact upon the speed of sound. A sound wave will travel faster in a less dense material than a more dense material. Thus, a sound wave will travel nearly three times faster in Helium as it will in air. This is mostly due to the lower mass of Helium particles as compared to air particles.The speed of a sound wave in air depends upon the properties of the air, namely the temperature and the pressure. The pressure of air (like any gas) will affect the mass density of the air (an inertial property) and the temperature will affect the strength of the particle interactions (an elastic property). At normal atmospheric pressure, the temperature dependence of the speed of a sound wave through air is approximated by the following equation:

v = 331 m/s + (0.6 m/s/C)oT

where T is the temperature of the air in degrees Celsius. Using this equation to determine the speed of a sound wave in air at a temperature of 20 degrees Celsius yields the following solution.v = 331 m/s + (0.6 m/s/C)oT v = 331 m/s + (0.6 m/s/C)o(20 C)v = 331 m/s + 12 m/sv = 343 m/s(The above equation relating the speed of a sound wave in air to the temperature provides reasonably accurate speed values for temperatures between 0 and 100 Celsius. The equation itself does not have any theoretical basis; it is simply the result of inspecting temperature-speed data for this temperature range. Other equations do exist which are based upon theoretical reasoning and provide accurate data for all temperatures. Nonetheless, the equation above will be sufficient for our use as introductory Physics students.) Using Wave Speed to Determine DistancesAt normal atmospheric pressure and a temperature of 20 degrees Celsius, a sound wave will travel at approximately 343 m/s; this is approximately equal to 750 miles/hour. While this speed may seem fast by human standards (the fastest humans can sprint at approximately 11 m/s and highway speeds are approximately 30 m/s), the speed of a sound wave is slow in comparison to the speed of a light wave. Light travels through air at a speed of approximately 300 000 000 m/s; this is nearly 900 000 times the speed of sound. For this reason, humans can observe a detectable time delay between the thunder and the lightning during a storm. The arrival of the light wave from the location of the lightning strike occurs in so little time that it is essentially negligible. Yet the arrival of the sound wave from the location of the lightning strike occurs much later. The time delay between the arrival of the light wave (lightning) and the arrival of the sound wave (thunder) allows a person to approximate his/her distance from the storm location. For instance if the thunder is heard 3 seconds after the lightning is seen, then sound (whose speed is approximated as 345 m/s) has traveled a distance ofdistance = v o t = 345 m/s o 3 s = 1035 mIf this value is converted to miles (divide by 1600 m/1 mi), then the storm is a distance of 0.65 miles away.Another phenomenon related to the perception of time delays between two events is an echo. A person can often perceive a time delay between the production of a sound and the arrival of a reflection of that sound off a distant barrier. If you have ever made a holler within a canyon, perhaps you have heard an echo of your holler off a distant canyon wall. The time delay between the holler and the echo corresponds to the time for the holler to travel the round-trip distance to the canyon wall and back. A measurement of this time would allow a person to estimate the one-way distance to the canyon wall. For instance if an echo is heard 1.40 seconds after making the holler, then the distance to the canyon wall can be found as follows:distance = v o t = 345 m/s o 0.70 s = 242 mThe canyon wall is 242 meters away. You might have noticed that the time of 0.70 seconds is used in the equation. Since the time delay corresponds to the time for the holler to travel the round-trip distance to the canyon wall and back, the one-way distance to the canyon wall corresponds to one-half the time delay.While an echo is of relatively minimal importance to humans, echolocation is an essential trick of the trade for bats. Being a nocturnal creature, bats must use sound waves to navigate and hunt. They produce short bursts of ultrasonic sound waves which reflect off objects in their surroundings and return. Their detection of the time delay between the sending and receiving of the pulses allows a bat to approximate the distance to surrounding objects. Some bats, known as Doppler bats, are capable of detecting the speed and direction of any moving objects by monitoring the changes in frequency of the reflected pulses. These bats are utilizing the physics of the Doppler effect discussed in. This method of echolocation enables a bat to navigate and to hunt.

Speed = Wavelength o Frequency

Using the symbols v, , and f, the equation can be rewritten as

v = f o

The above equation is useful for solving mathematical problems related to the speed, frequency and wavelength relationship. However, one important misconception could be conveyed by the equation. Even though wave speed is calculated using the frequency and the wavelength, the wave speed is not dependent upon these quantities. An alteration in wavelength does not affect (i.e., change) wave speed. Rather, an alteration in wavelength affects the frequency in an inverse manner. A doubling of the wavelength results in a halving of the frequency; yet the wave speed is not changed. The speed of a sound wave depends on the properties of the medium through which it moves and the only way to change the speed is to change the properties of the medium.

Sound is waveform in matter

Sound is a waveform that travels through matter. Although it is commonly associated in air, sound will readily travel through many materials such as water and steel. Some insulating materials absorb much of the sound waves, preventing the waves from penetrating the material.

Does not travel in vacuum

Because sound is the vibration of matter, it does not travel through a vacuum or in outer space. When you see movies or TV shows about battles in outer space, you should only be able to see an explosion but not hear it. The sounds are added for dramatic effect.

Note that in outer space, there are actually some widely-spaced atoms and molecules floating around. But since they are so far apart, regular wave motion would not be great enough to detect.

Sound waves different than light waves

Also note that light and radio waves are electromagnetic waves. They are completely different than sound, which is vibration of matter. Electromagnetic waves are related to electrical and magnetic fields and readily travel through space.

The back-and-forth vibration of an object creates the compression waves of sound. The motions of a loudspeaker cone, drumhead and guitar string are good examples of vibration that cause compression waves. This is different than the up and down or transverse motion of a water wave. Transverse Wave (water wave)Compression Wave (sound)The illustration above shows a comparison of a transverse wave such as a water wave and the compression wave sound wave.

Characteristics of sound

A sound wave has characteristics just like any other type of wave, including amplitude, velocity, wavelength and frequency.

The amplitude of a sound wave is the same thing as its loudness. Since sound is a compression wave, its loudness or amplitude would correspond to how much the wave is compressed. It is sometimes called pressure amplitude.

Decibel

A common measurement of loudness is the decibel (dB). It is really 1/10 of a bel, which was named after the inventor of the telephone, Alexander Graham Bell. It is a complex unit that varies as the ratio of the logarithms of loudness.

Decrease in loudness

A sound wave will spread out after it leaves its source, decreasing its amplitude or loudness. The amplitude decreases as the square of the distance from the source. Also, if there is some absorption in the material, the loudness of the sound will decrease as it moves through the substance.

The speed or velocity of sound in air is approximately 344 meters/second, 1130 feet/sec. or 770 miles per hour at room temperature of 20oC (70oF). The speed varies with the temperature of air, such that sound travels slower at higher altitudes or on cold days.Note: The difference between speed and velocity is that velocity usually includes direction the of travel. We'll interchange them here, but in some cases the distinction is important.A jet plane traveling at the speed of sound would be moving at about 680 mph at sea level. At very high altitudes, the speed required would be much lower.

Wavelength is the distance from one crest to another of a wave. Since sound is a compression wave, the wavelength is the distance between maximum compressions.

Frequency

The frequency of sound is the rate at which the waves pass a given point. It is also the rate at which a guitar string or a loud speaker vibrates. Frequency is also called the pitch of a sound. It is called the note in musical sounds.

The relationship between velocity, wavelength and frequency is: velocity = wavelength x frequencySince the velocity of sound is approximately the same for all wavelengths, frequency is often used to better describe the effects of the different wavelengths.

The pitch or note of a sound that we experience is determined by its wavelength or its frequency. The shorter the wavelength, the higher the frequency becomes, and the higher the pitch that we hear.

Creating and detecting sounds

Creating and detecting sounds are similar effects, but opposite. They demonstrate the duality of nature.

Whenever an object in air vibrates, it causes compression waves in the air. These waves move away from the object as sound. There are many forms of the vibration, some not so obvious.The back and forth movement of a loudspeaker cone, guitar string or drum head result in compression waves of sound. When you speak, your vocal cords also vibrate, creating sound.Blowing across a bottle top can also create sound. In this case, the air inside the bottle goes in a circular motion, resulting in sound waves being formed. Wind blowing through trees can also create sound this indirect way.Sound can also be created by vibrating an object in a liquid such as water or in a solid such as iron. A train rolling on a steel railroad track will create a sound wave that travels through the tracks. They will then vibrate, creating sound in air that you can hear, while the train may be a great distance away.

When a sound wave strikes an object, it can cause the object to vibrate. This leads to the method to detect sound, which requires changing that vibration into some other type of signal-usually electrical.The main way you detect or sense sounds is through your ears. The sound waves vibrate your ear drum, which goes to the inner ear and is changed to nerve signals you can sense.You can also feel sounds. Stand in front of a stereo or hi-fi loudspeaker on at full volume, and you can feel some of the vibrations from the music.There are mechanical devices that detect sounds, such as the microphone. The sound vibrates a membrane, which creates an electric signal that is amplified and recorded.…to be continued    ..1472 pages.

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