Category Sound

            Sonomicrometry is a technique that makes use of the transmission of ultrasound energy through certain type of crystals and tissues to measure distance.

            It has a variety of applications, including measuring the distance between two fixed points in a soft tissue environment, and, quantifying the function and dynamics of cardiac, skeletal or smooth muscles. Traditionally, this technique has been used to determine cardiac function on large research animals like dogs, sheep, pigs etc. It was first done by Dean Franklin in 1956, and was quickly adopted by other biologists.

            At present, sonomicrometry is the most prevalent method to determine muscle length changes during animal locomotion, feeding and other bio-mechanical functions. Sonomicrometry crystals are usually implanted inside the skeletal or cardiac muscle tissues to track length changes during activities such as heart-beat, chewing etc. However, sonomicrometer devices cannot be used to treat or diagnose medical conditions in animals or humans.

           Animals are always thought to be intelligent enough to sense changes in environment. But a few studies in recent times suggest that some birds too are equally smart. For example, the golden winged warblers.

            In April 2014, a massive thunderstorm caused a series of tornadoes to tear through the Southern and Central United States. But something interesting happened just a day or two before this disaster – large flocks of golden winged warblers fled the area. Scientists say that the birds’ behaviour was caused by their ability to sense infrasound, which was an early warning sign.

            Other species that are sensitive to weather changes are seagulls and African guinea fowls. Apparently, seagulls get to hear low frequency sounds caused by large storms and also, earthquakes. This prompts them to fly inland before these disasters happen. So also is the case with African guinea fowls – they predict weather and change their nature accordingly.

            There are many animals that use infrasound for communication. One of the best examples is the elephant. Research has proved that the vocal communication of these mammals ranges down into lower frequencies. As a result, the sound waves get carried farther, and reach elephant groups that are located very far away.

            Interestingly, tigers also produced infrasound, along with a variety of other sounds. This is said to help them maintain their hunting grounds. Their low frequency sounds at 18 Hz and below, most of which are inaudible to humans, drive away rivals from their territory, and also attract mates. Such sounds not only cover long distances, but also penetrate dense forests.

            In addition to these two, there are many other animals that produce infrasound. Examples of these are giraffes, alligators, hippos, and marine mammals like humpback whales.

            Since time immemorial, there have been stories, legends, and reports on the sensitivity of animals towards different kinds of sounds.

            But the most commonly heard reports are on how some animals detect infrasonic sounds before natural disasters. As per one of the latest reports, animals like buffaloes, goats and dogs were found unharmed along the Cuddalore coast of India, where thousands died following the tsunami of 2004. People around the region said that many animals fled the area hours before the incident took place.

            Another group of animals that are said to have the ability to sense disasters are cats. Not just smaller animals, large once like elephants too grow restless prior to dangerous natural occurrences.

            Although many studies have been made, the reason for such strange behaviour in animals is yet to be confirmed.

            Infrasound can be defined as the low-frequency sound that is below 20 Hertz.

            For this reason, it cannot be heard by the human ear. Animals, on the other hand, are sensitive to such sounds. Research has proved that some of them can sense infrasonic sounds from natural events like earthquakes and volcanoes, and act accordingly. They can also use it for communication between each other.

            There are many uses of infrasonic sound. Primarily, it can be used to detect volcanic eruptions. Scientists use infrasound to track the passage of meteors through the atmosphere.

            There are many sources from where infrasound can come. They include large natural events like earthquakes, avalanches, volcanoes, and extreme weather events.

            In addition, man-made events such as explosions, wind turbines, aircraft breaking the sound barrier, and certain speakers too, produce it.

            The special characteristic of infrasound is its ability to cover long distances and get around obstacles with little dissipation.

            In the case of medical scans and non-destructive testing, experts use relatively low strength ultrasound waves. Much stronger waves are used for removing unwanted deposits like painful stones.

            Let us make it clearer. If we have problems caused by stones in kidney, gall bladder, or liver, powerful ultrasound waves are fired from outside our body in order to make the stone vibrate, and disintegrate. For this purpose, doctors now use what is known as an ultrasonic gun, which causes relatively lesser pain. The gun forces out short bursts of high frequency vibrations that cause the stones to resonate. These then smash the stones into pieces.

            A similar technique is used to destroy cancerous tumours and damaged regions of the brain called lesions. Here, ultrasound energy is applied to heat in order to destroy diseased tissues.