Sounds Right

The next time you go out into the country – sit a while with your eyes closed. Soon your ears will take over to tell you stories you might have missed completely, before, says BITTU SAHGAL

The environment that we live in is almost never silent. At every conscious moment we are aware of the sounds and noises around us. We learn to block out some sounds, while others we deal with directly. The sound of the crash and clang of falling dishes and hammering instruments, the distant rumble of traffic and trains, the crunch of someone’s footsteps on the gravel, the patter of raindrops and the ticking of the clock in the room. And out in the open – the rustle of leaves, chirping of birds and various other sounds of nature. Different sounds, even out of their natural settings, produce different associations for us, as they also do for animals. Thus the ringing of a bell could mean food for your hungry pet dog just as it could mean school bell for kids! Sound is produced by vibrating bodies. See how this works by performing a series of simple experiments. Tie a loop of tough string in a hole near one end of a ruler and holding the loop with your fingers keep swinging the ruler in a vertical circle. What do you hear? Hold a ruler down tight on the table with three fourths of it jutting over the side. Bend the side jutting over the table, slightly, and then let it go suddenly. The ruler, you will see, vibrates up and down. Do you hear anything as it is vibrating? Draw it a little further onto the table so that a lesser part of the ruler overhangs. Repeat the procedure. Is there any difference in the sound produced?

What is the exact meaning of a vibrating object, how do vibrations differ and how does this influence sound? To find these answers for yourself, take a small, heavy object such as a stone, and tie one metre of strong string to it. Hang the object in a doorway or from the ceiling and let it swing freely. How many times will it swing per minute? With a stronger string does the number of swings vary? Yes, it will. A shorter string produces faster and quicker vibrations. The interesting thing is that slower vibrations — say 16 times per second — produce a sound that is very low. While faster vibrations give rise to higher notes. Vibrations at 20,000 times per second produce the highest note that man can hear. You can test this principle by blowing across the mouth rims of empty bottles. You’ll find that a low note will be produced from a fairly large-mouthed bottle, whereas a thin, narrow tube, for instance, will produce a high-pitched sound.

Air, solids and liquids all serve to carry sound. Try this out yourself. A person making noise in a room can be heard distinctly. But, if he moves away to another room he will not be so clear. If you place a clock inside an airless jar you will not be able to hear the ticking at all, even if it is right beside you! Liquids carry sound four times faster than air does. If you put your head under water (inside a swimming pool, tub or basin) and someone else strikes a gong, also under water, the sound will travel clearly through water. Amongst living things, the actual process of making sounds or singing is directly related to the structure of the life form. Arthropods (crabs, insects, spiders, centipedes, etc.) produce noises by scraping and tapping various parts of their hard external skeletons together. Land creatures use their respiratory systems. This, over the ages, has been specialized and refined to produce highly distinct sounds. Different sounds put together in different ways produce unique results. One syllable or a series of short syllables from a bird may result in a chirp. Repeated chirps can make up a song or a trill. While some sounds are monotonous and repetitive, others change and vary in harmony to sound extremely musical.

Among insects, the loudest and perhaps the most musical are the male members of the Orthoptera (crickets, grasshoppers and their various relatives) and bugs of the order Homoptera (cicadas and leaf hoppers). Grasshoppers create songs by scraping their legs against their folded wings thus producing a long sequence of chirps. Crickets sing by rubbing their forewings together. The under portion of their bodies have veins bearing teeth, which are caught by a scraper on the other wing. The loud pulsating songs of cicadas are produced by special organs on either side of the insect’s abdomen. Cicadas often sing in groups and so sound extremely loud to humans. Many other insects produce single squeaks and hisses that serve to warn off predators. There are certain pistol shrimps that snap their claws shut with an explosive sound, exactly like the pistol going off, as you may have guessed from the name. This stuns fish swimming at close range! Fish too communicate using sound; and we’ve all heard frogs and toads croaking for all their worth, a sound that is produced by the amphibian’s vocal cords and amplified by throat sacs.

So sound, as we can see and also well imagine, is an intrinsic part of the living world. Sounds help animals find mates, or simply keeping flocks or herds together. As in the case of human, sounds convey love, aggression or fright. Do you want some ‘sound advice’? The next time you go out into the country – sit a while with your eyes closed. Soon your ears will take over to tell you stories you might have missed completely, before. And don’t forget to write your observations in your nature diary, for the joy of recognising sounds can be relived many, many years later.