How to Make Sound Louder

One day Lenya invented a new "buzzer." It was a comb. When you pluck a tooth, the comb squeaks, but it's very quiet. Lenya brought the comb to his ear - now he could hear it well and loudly, but there was a problem: Lenya could hear it fine, but Irishka, who was drawing at the table, couldn't hear it at all. Lenya put the comb against his forehead - again, only he could hear it well. Finally, he figured it out and put the comb against the table. He plucked a tooth, and the comb rang out loud! Irishka tore herself away from her drawing and looked at what Lenya was doing. And Lenya started putting the comb against everything he could see: against the window, against the door, against the piano... And every time he put the comb against a solid object, the comb squeaked loudly, but when he held it in the air, it squeaked weakly.

Tanya became interested in this discovery too. She rolled a megaphone from a sheet of paper and said to Lenya:

"Put the comb against the megaphone."

Lenya put the comb against the megaphone, plucked a tooth, and the comb squeaked loudly.

"That's great!" the children said in unison.

"Why does it come out louder with the megaphone?" asked Tanya.

The children didn't know.

So Tanya explained:

"When a tooth vibrates, it makes the air around it vibrate, but the tooth is small and vibrates little air. That's why the sound comes out quiet."

Then Irinushka said:

"When we put the comb against the megaphone, the megaphone vibrated along with the comb, right? The megaphone is also bigger than the tooth, so it vibrates much more air than the tooth of the comb. That's why the sound comes out louder."

Irishka, of course, immediately started explaining:

"Even though the table vibrated weakly from the comb, it's big and vibrates much more air than the tooth of the comb, so the sound comes out loud."

After everyone understood why sound comes out loud, the children took a stick and nailed small nails at both ends. They stretched wire over the nails, and to the bottom end they attached a megaphone. Tanya brought a violin bow and gave it to Irishka, saying:

"We've made ourselves an amazing cello."

Tanya sat down at the piano. Irishka took the bow in one hand, and with the fingers of her other hand she began pressing the wire-string. Lenya held the megaphone so it wouldn't fall to the floor. And together they all started playing the song "Chizhik-Pyzhik." The sound from the homemade cello was like the roar of a hungry bear woken up in winter. The cello roared, but it still turned out well - loud and funny!

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To make a "cello," it's best to take a simple stick, round or rectangular in cross-section. The thickness of this stick should be such that a child can easily grasp it with their palm. Instead of a guitar fretboard, you should nail a small piece of wood to the top end of the stick, to which you can tie thin wire about 0.5-1 mm thick. It's better to use one of the bass (wound) strings from a guitar for this purpose. You should nail a second small nail to the bottom end of the stick and attach the other end of the wire to it after stretching it. By stretching the wire and plucking it lightly with your fingers, you can achieve a low, velvety tone. After the string is stretched at a distance of no more than 5 mm from the bottom nail, you should attach a paper megaphone with a needle. The most suitable material for this is drawing paper or cardboard. It's best to roll a large megaphone from many sheets of paper. The wide end of the megaphone should be tied to the top end of the stick. You can play this cello with fingers and by plucking. To prevent the string from touching the stick during play, you should place a match or piece of wood near the nails, or make notches in the stick at these same places from a thick wire loop. If you have a piano, guitar, or some other musical instrument at home, try playing the "cello" with accompaniment.

"It is possible to make a few more instruments with the children still. Place several (7-8) champagne glasses, liqueur glasses or regular glasses on the table (it's best to use glasses with smooth edges). Pour different quantities of water in them. As you pour, keep tapping lightly on the edge with a pencil. As you do this, you can hear that the sound gets lower as the glasses are filled up with water. You just need to make sure there are no air bubbles on the sides of the glass, so that they will make the sound dull and featureless. Removing them is easy if you run the finger along the side of the glass. And to make it so they don't appear, it's best to pour warm water which has been boiled. Using a piano, accordion, a children's xylophone or simply by ear, tune the glasses to a scale, for example C major. Try to play something on this unusual 'instrument'.

"From dry hollow sticks you can make a good xylophone. To saw them from wood, you need to take sticks of the same thickness but different lengths. You can hang them by their ends, you can drill holes in them and string them on a strong thread, or you can simply lay them out. By tapping on them, a child can determine by ear which stick gives the highest sound and which the lowest. By sawing holes of different diameters in the sticks, the child also gets different sounds. By tuning the sticks with intermediate tones, you can achieve "contrast." Make two thin plates from metal or plastic (for example, from a bottle cap - 4-5 cm), bend them in the middle so that they resemble small hammers, and use these hammers to tap on the sticks or resonators. The hammers in this case serve as resonators, amplifying the sound."