My Science School

            An amplifier is a device used to increase or strengthen the power of a signal. They can be seen in audio equipment of all kinds.

            Let’s take the example of a hearing aid. It has a microphone that picks up sounds from all around and converts them to electric signals that constantly changes in strength. Here, an amplifier takes the signals, and boosts it many times before feeding it into the tiny loudspeaker placed inside the ear canal. The sound thus produced is ‘amplified’ before it reaches the person. That means, the duty of the amplifier is to convert a small electric current into a larger one.

     

 

            Depending on their functions, amplifiers can be categorized as weak-signal amplifiers or power amplifiers. The former is designed to deal with exceedingly small input signals. They are used in audio tape players, CD players tec. History notes that the first electronic device that could amplify was the triode vacuum tube, invented by Lee De Forest in 1906.

            Loudspeakers are equipments that we all are familiar with it. By definition, a loudspeaker is a tool that converts an electrical signal into sound waves to provide the most faithful reproduction that is feasible for its design. The most widely used type of loudspeaker is the dynamic speaker. The moving coil principle commonly used today in speakers was patented by Edward W. Kellogg and Chester W. Rice in 1924.

            Depending on the range of frequencies, loudspeakers can be divided into four- subwoofers, woofers, mid-range loudspeakers and tweeters.

            

Continue reading "What is a loudspeaker?"

            Developed in the 1870s by Englishman David Edward Hughes, carbon microphones were the first reliable form of microphones. They were widely used for many years before being replaced by other types that showed better performance.

            Structurally, a carbon microphone comprises carbon granules within a small container that is covered by a thin metal diaphragm. It requires a battery to cause current flow. By compressing and decompressing the carbon, sound waves change the amount of electric current flowing through the wire. This, in turn, creates electrical waves.

            The biggest disadvantage of carbon microphones was that they had a limited frequency and would not reproduce music effectively.

            On the basis of application, microphones can be divided into different types. The three most common ones are – dynamic microphones, condenser microphones and ribbon microphones. Let’s look at them in detail.

            Dynamic microphones are the most common and durable types, well suited for live sound. They work on the principle of electromagnetic induction, but take loud signals to move the coils.

            The next type of microphones is condensers. They use electrically charged capsules that are far more sensitive than moving coils of the dynamic mic.

            There are both large diaphragm condenser mics and small diaphragm condenser mics. The former is best suited for recording vocals, while the latter is great for high frequency instruments like acoustic guitar and cymbals.

            Ribbon microphones use corrugated metal ribbons that vibrate when pushed by air. But today, they are no longer popular. There is also a microphone known as the piezoelectric microphone. It uses a crystal of piezoelectric material to produce sound.

 

            A microphone, popularly called a mic, is a device we are all familiar with. It is in fact a part of our daily life and can be seen in almost all equipment around us. For example, computers, telephones, televisions, transmitters for commercial radio, tape recorders, hearing aids and public address systems for concert halls, all of them uses microphone.

            Technically, a microphone is a device that converts mechanical energy waves or sound into electrical energy waves.

            Let us see how the device works. When we speak, sound waves carry energy toward the microphone. Inside it, there is something called a diaphragm, which moves back and forth when hit by the waves. As a result, the coil attached to the diaphragm too moves back and forth. This results in the production of electric current, which flows out from the mic to an amplifier, or a sound recording device. Subsequently, the voice of the speaker is heard a loud. This is how personal address systems, electric guitars amplifiers etc. work.

            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.

             Some of the most important applications of ultrasonics can be seen in the field of medicine. Ultrasonography or ultrasonic scanning is one of it, which uses high frequency sound waves to produce images of internal organs, vessels and tissues. This type of scanning is used to diagnose the condition of organs such as liver, kidneys or gallbladder.

            Then, there is something called obstetric ultrasound. It is a technique used during pregnancy to create images of a baby inside the womb.

 

       

 

 

    Another public health application of ultrasonics is in dental care. It enables the equipment called ‘descalers’ to remove plaque from teeth through a smoother and less painful experience.

            Yet another important use can be seen in the cleaning of equipment. What makes ultrasonic technology so popular in medicine is its effectiveness and affordability.

            Acoustic microscopy is a technology that helps in visualizing tiny structures using high frequency ultra sound waves. The microscopes in this fashion penetrate solid materials and create visible images of internal features, including defects like cracks and voids. For this purpose, they use frequencies up to several gigahertz.

             One of the most advanced types of acoustic microscopy is scanning acoustic microscopy. Here, the internal parts of a sample can be viewed without staining or causing any damage. It relies on a beam to scan the sample while it is in water.

            The difference between a traditional microscope and an acoustic microscope is that the former allows us to see only the surface of a specimen, while the latter obtains images from deeper layers. It also takes accurate measurements at a micro-level, which other microscopes may not be able to obtain.

          Just like humans, all forms of life in the Universe have the ability to hear, or sense things around them. But some of them have exceptional features for hearing, which enable them to survive better than others.

          One such animal is the elephant. Its hearing frequency is somewhere between 16 and 12,000 hertz, as a result of which, it can hear at a frequency 20 times lower than us.

          Another mammal that has a special auditory system is the fennec fox. It is a small species of fox seen in the sandy Sahara. It has large ears that play a vital role in hearing, as well as keeping the animal cool by spreading out during high temperatures. Other than these two, there are many animals that are sensitive to sounds. These include pigeons, owls, dolphins, etc. 

            As a matter of fact, no two species of animals look alike, or behave alike. Similarly, the abilities and senses of animals vary too, from species to species.

            One cannot expect a monkey to have the hearing ability of an elephant, nor can auditory ability between a marine mammal and a terrestrial animal be compared. Generally, it is seen that larger animals hear and use low frequency sounds, while smaller ones have with higher frequencies.

            However, there are always exceptions, as in the case of spade foot toads that can easily pick up low-frequency sounds. These are animals that live in desert habitats and spend their days buried in ground during dry seasons. They come out only when pools are formed after infrequent rains. And that is when their young ones are developed, before the water dries up.

            Similar to animals, birds and insects too have peculiar auditory features that help them adapt to surroundings.