Report: Sound sources. Sound vibrations. Sound frequency

Sound sources.

Sound vibrations

Lesson summary.

1.Organizational moment

Hello guys! Our lesson has wide practical application in everyday practice. Therefore, your answers will depend on your observation skills in life and your ability to analyze your observations.

2. Repetition of basic knowledge.

Slides No. 1, 2, 3, 4, 5 are displayed on the projector screen (Appendix 1).

Guys, here is a crossword puzzle, after solving it you will learn the key word of the lesson.

1st fragment: name a physical phenomenon

2nd fragment: name the physical process

3rd fragment: name a physical quantity

4th fragment: name a physical device

	R		Z		N
	IN
						U
						TO

Pay attention to the highlighted word. This word is “SOUND”, it is the key word of the lesson. Our lesson is devoted to sound and sound vibrations. So, the topic of the lesson is “Sound sources. Sound vibrations" During the lesson you will learn what is the source of sound, what sound vibrations are, their occurrence and some practical applications in your life.

3. Explanation of new material.

Let's conduct an experiment. Purpose of the experiment: to find out the causes of sound.

Experiment with a metal ruler(Appendix 2).

What did you observe? What can be concluded?

Conclusion: a vibrating body creates sound.

Let's carry out the following experiment. Purpose of the experiment: to find out whether sound is always created by a vibrating body.

The device you see in front of you is called fork.

Experiment with a tuning fork and a tennis ball hanging on a string(Appendix 3) .

You hear the sound that the tuning fork makes, but the vibration of the tuning fork is not noticeable. To make sure that the tuning fork is oscillating, we carefully move it towards a shady ball suspended on a thread and we will see that the oscillations of the tuning fork are transferred to the ball, which begins to move periodically.

Conclusion: sound is generated by any vibrating body.

We live in an ocean of sounds. Sound is created by sound sources. There are both artificial and natural sources of sound. TO natural sources sound include vocal cords (Appendix 1 - slide No. 6). The air we breathe leaves the lungs through Airways into the larynx. The larynx contains the vocal cords. Under the pressure of exhaled air they begin to oscillate. The role of the resonator is played by the oral and nasal cavities, as well as the chest. For articulate speech, in addition to the vocal cords, you also need the tongue, lips, cheeks, soft palate and epiglottis.

Natural sources of sound also include the buzzing of a mosquito, fly, bee ( wings flutter).

Question:what creates sound.

(The air in the ball is under pressure in a compressed state. Then it expands sharply and creates a sound wave.)

So, sound creates not only a oscillating, but also a sharply expanding body. Obviously, in all cases of sound occurrence, layers of air move, i.e., a sound wave arises.

The sound wave is invisible, it can only be heard and also registered by physical instruments. To register and study properties sound wave We will use a computer, which is currently widely used by physicists for research. A special research program is installed on the computer, and a microphone is connected that picks up sound vibrations (Appendix 4). Look at the screen. On the screen you see graphical representation sound vibration. What is this schedule? (sinusoid)

Let's conduct an experiment with a tuning fork with a feather. We hit the tuning fork with a rubber mallet. Students see the vibration of the tuning fork, but do not hear any sound.

Question:Why are there vibrations, but you don’t hear the sound?

It turns out, guys, that the human ear perceives sound ranges ranging from 16 Hz to Hz, this is audible sound.

Listen to them through a computer and notice the change in the frequencies of the range (Appendix 5). Pay attention to how the shape of the sine wave changes when the frequency of sound oscillations changes (the oscillation period decreases, and therefore the frequency increases).

There are sounds that are inaudible to the human ear. These are infrasound (oscillation range less than 16 Hz) and ultrasound (range greater than Hz). You see a diagram of frequency ranges on the board, sketch it in your notebook (Appendix 5). By studying infra and ultrasound, scientists have discovered a lot interesting features these sound waves. About these interesting facts Your classmates will tell us (Appendix 6).

4. Consolidation of the studied material.

To reinforce the material learned in class, I suggest playing a TRUE-FALSE game. I read out the situation and you hold up a sign that says TRUE or FALSE and explain your answer.

Questions. 1. Is it true that the source of sound is any oscillating body? (right).

2. Is it true that in a hall filled with people the music sounds louder than in an empty one? (wrong, because the empty hall acts as a vibration resonator).

3. Is it true that a mosquito flaps its wings faster than a bumblebee? (correct, because the sound produced by a mosquito is higher, therefore the frequency of wing vibrations is higher).

4. Is it true that the vibrations of a sounding tuning fork die out faster if its leg is placed on a table? (correct, because the vibrations of the tuning fork are transmitted to the table).

5. Is it true that the bats see with sound? (correct, because bats emit ultrasound and then listen to the reflected signal).

6. Is it true that some animals “predict” earthquakes using infrasound? (true, for example, elephants feel an earthquake several hours in advance and are extremely excited).

7. Is it true that infrasound causes mental disorders in people? (that's right, in Marseille (France) next to scientific center A small factory was built. Soon after its launch in one of scientific laboratories discovered strange phenomena. After staying in her room for a couple of hours, the researcher became absolutely stupid: he had difficulty solving even a simple problem).

And in conclusion, I suggest that you get the key words of the lesson from the cut letters by rearranging them.

KVZU – SOUND

RAMTNOCKE – TUNING FORK

TRYAKZUVLU – ULTRASOUND

FRAKVZUNI - INFRASOUND

OKLABEINYA – OSCILLATIONS

5. Summing up the lesson and homework.

Lesson summary. During the lesson we found out that:

That any vibrating body creates sound;

Sound travels through the air in the form of sound waves;

Sounds are audible and inaudible;

Ultrasound is an inaudible sound whose vibration frequency is above 20 kHz;

Infrasound is an inaudible sound with an oscillation frequency below 16 Hz;

Ultrasound is widely used in science and technology.

Homework:

1. §34, ex. 29 (Peryshkin 9th grade)

2. Continue the reasoning:

I hear the sound of: a) flies; b) a fallen object; c) thunderstorms, because...

I don’t hear the sound: a) from a climbing dove; b) from an eagle soaring in the sky, because...

The purpose of the lesson: Form an idea of ​​sound.

Lesson objectives:

Educational:

• create conditions for activating students’ knowledge of sound obtained during the study of natural sciences,
• contribute to the expansion and systematization of students' knowledge about sound.

Educational:

• continue to develop the ability to apply knowledge and personal experience in different situations,
• promote the development of thinking, analysis of acquired knowledge, highlighting the main thing, generalization and systematization.

Educational:

• promote the formation of a caring attitude towards oneself and others,
• promote the formation of humanity, kindness, responsibility.

Lesson type: revealing content.

Equipment: tuning fork, ball on a string, air bell, reed frequency meter, set of disks with different numbers of teeth, postcard, metal ruler, multimedia equipment, disk with a presentation developed by the teacher for this lesson.

During the classes

Among the various oscillatory and wave movements found in nature and technology, sound vibrations and waves, and just sounds, are especially important in human life. IN Everyday life- These are most often waves propagating in the air. It is known that sound also propagates in other elastic media: in the ground, in metals. Having plunged headlong into the water, you can clearly hear the sound of the engine of an approaching boat from a distance. During a siege, “listeners” were placed within the fortress walls to monitor the enemy’s excavation work. Sometimes these were blind people whose hearing was especially acute. Based on the sounds transmitted in the Earth, for example, an enemy tunnel to the walls of the Zagorsk Monastery was promptly discovered. Thanks to the presence of a hearing organ, a person receives large and varied information from the environment with the help of sounds. Human speech is also produced through sounds.

On the table in front of you are worksheets with lines from Charles Dickens's The Hearth Cricket. Each of you must underline those words that express sound.

1 option

• The frightened mower came to his senses only when the clock stopped shaking under him, and the grinding and clanging of its chains and weights finally stopped. No wonder he was so excited: after all, this rattling, bony watch is not a watch, but a mere skeleton! - are capable of making anyone afraid when they start clicking bones...
• ….It was then, mind you, that the teapot decided to have a pleasant evening. Something began to bubble uncontrollably in his throat, and he began to emit a sharp, ringing snort, which he immediately cut off, as if he had not yet finally decided whether he should now show himself to be a sociable fellow. Then, after two or three vain attempts to drown out the desire for sociability, he threw away all his gloominess, all his restraint and burst into such a cozy, such a cheerful song that no crybaby nightingale could keep up with him...
• ….The teapot sang its song so cheerfully and cheerfully that its entire iron body hummed and bounced over the fire; and even the lid itself began to dance something like a jig and knock on the teapot (grinding, clanging, rattling, clicking, sonorous snorting, singing, singing, singing, humming, knocking).

Option 2:

• This is where, if you like, the cricket really began to echo the teapot! He picked up the chorus so loudly in his own chirping way - clack, clatter, clatter! - his voice was so strikingly disproportionate to his height compared to the teapot that if it had immediately exploded, like a gun with too much charge, it would seem to you a natural and inevitable end, towards which he himself was striving with all his might .
• ….The teapot no longer had to sing solo. He continued to play his part with undiminished zeal, but the cricket seized the role of first violin and held it. My God, how he chirped! His thin, sharp, piercing voice rang throughout the house and, probably, even twinkled like a star in the darkness, behind the walls. Sometimes, at the loudest sounds, he would suddenly let out such an indescribable trill that it involuntarily seemed as if he himself was jumping high in a fit of inspiration, and then falling back to his feet. Nevertheless, they sang in complete agreement, both the cricket and the teapot... The theme of the song remained the same, and as they competed, they sang louder, and louder, and louder. (loud, chorus, chirping mode - strek, strek, strek, burst, solo, chirped, sharp, shrill voice, rang, loud sounds, trill, sang, songs, sang, louder)

We live in a world of sounds. The branch of physics that studies sound phenomena is called acoustics (slide 1).

Sources of sound are vibrating bodies (slide 2).

“Everything that sounds necessarily vibrates, but not everything that vibrates sounds.”

Let us give examples of bodies that vibrate but do not sound. Frequency meter reeds, long ruler. What examples can you give? (a branch in the wind, a float on the water, etc.)

Let's shorten the ruler and hear the sound. The air bell also makes sounds. Let us prove that a sounding body vibrates. To do this, let's take a tuning fork. The tuning fork is an arc-shaped rod mounted on a holder; hit it with a rubber mallet. By bringing a sounding tuning fork to a small ball hanging on a thread, we will see that the ball is deflected.

If we pass a sounding tuning fork across glass covered with soot, we will see a graph of the tuning fork's vibrations. What is this graph called? ( tuning fork vibrates harmonics)

Sound sources can be liquid bodies, and even gases. The air hums in the chimney and the water sings in the pipes.

What examples of sound sources can you give? ( mechanical watch, boiling kettle, sound made by an engine)

When a body sounds, it vibrates, its vibrations are transmitted to nearby air particles, which begin to vibrate and transmit the vibrations to neighboring particles, and they, in turn, transmit the vibrations further. As a result, sound waves are formed and propagated in the air.

A sound wave represents zones of compression and rarefaction of an elastic medium (air), a sound wave is a longitudinal wave (slide 3).

We perceive sound through our organ of hearing – the ear.

(One of the students tells how this happens) (slide 4).

(Another student talks about the dangers of headphones.)

“Having studied the behavior of young people in the capital’s metro for two months, experts came to the conclusion that in the Moscow metro every 8 out of 10 active users of portable electronic devices listen to music. For comparison: at a sound intensity of 160 decibels, the eardrums are deformed. The sound power reproduced by players through headphones is equivalent to 110–120 decibels. Thus, the impact on a person’s ears is equal to that of a person standing 10 meters from the roaring jet engine. If such pressure is applied to the eardrums every day, a person runs the risk of deafness. “Over the past five years, young boys and girls have begun to come to appointments more often,” otolaryngologist Kristina Anankina told NI. “They all want to be fashionable and constantly listen to music. However, prolonged exposure to loud music simply kills their hearing.” If after a rock concert the body needs several days to recover, then with a daily attack on the ears there is no time left to put the hearing in order. The auditory system ceases to perceive high frequencies."Any noise with an intensity of more than 80 decibels negatively affects inner ear, - says the candidate medical sciences, audiologist Vasily Korvyakov. – Loud music affects the cells responsible for the perception of sound, especially if the attack comes directly from the headphones. The situation is also worsened by vibration in the subway, which also negatively affects the structure of the ear. In combination, these two factors provoke acute hearing loss. Its main danger is that it occurs literally overnight, but curing it is very problematic." Due to noise exposure, the hair cells in our ear that are responsible for transmitting the sound signal to the brain die. But medicine has not yet found a way to restore these cells." .

The human ear perceives vibrations with a frequency of 16–20000 Hz. Everything below 16 Hz is infrasound, everything after 20,000 Hz is ultrasound. (slide 6).

Now we will listen to the range from 20 to 20,000 Hz, and each of you will determine your hearing threshold (slide 5).(See generator in Appendix 2)

Many animals hear infra- and ultra-sounds. Student speech (slide 6).

Sound waves travel in solids, liquids and gases, but cannot travel in airless space.

Measurements show that the speed of sound in air at 00C and normal atmospheric pressure is 332 m/s. As the temperature increases, the speed increases. For tasks we take 340 m/s.

(One of the students solves the problem.)

Task. The speed of sound in cast iron was first determined by the French scientist Biot as follows. At one end of the cast-iron pipe, a bell was struck; at the other end, the observer heard two sounds: first, one coming through the cast iron, and, after some time, a second, coming through the air. The length of the pipe is 930 meters, the time interval between the propagation of sounds turned out to be 2.5 seconds. Using these data, find the speed of sound in cast iron. The speed of sound in air is 340 m/s ( Answer: 3950 m/s).

Speed ​​of sound in various media (slide 7).

Soft and porous bodies are poor conductors of sound. To protect any room from the penetration of extraneous sounds, the walls, floor and ceiling are laid with layers of sound-absorbing materials. Such materials are: felt, pressed cork, porous stones, lead. Sound waves in such layers quickly attenuate.

We see how diverse sound is, let’s characterize it.

The sound produced by a harmoniously vibrating body is called a musical tone. Each musical tone (do, re, mi, fa, sol, la, si) corresponds to a certain length and frequency of the sound wave (slide 8).

Our tuning fork has a tone of A, frequency 440 Hz.

Noise is a chaotic mixture of harmonic sounds.

Musical sounds (tones) are characterized by volume and pitch, timbre.

A weak blow to the stem of the tuning fork will cause vibrations of small amplitude, and we will hear a quiet sound.

A strong blow will cause vibrations with greater amplitude, we will hear loud noise.

The loudness of a sound is determined by the amplitude of vibrations in a sound wave (slide 9).

Now I will rotate 4 disks, which different quantities teeth I will touch these teeth with a postcard. A disc with larger teeth has a higher frequency and a higher sound. A disc with fewer teeth has less vibration and a lower sound.

The pitch of a sound is determined by the frequency of sound vibrations. The higher the frequency, the higher the sound. (slide 10)

The highest human soprano note is around 1300 Hz

The lowest human bass note is around 80 Hz.

Who has a higher tone - a mosquito or a bumblebee? Who do you think flaps its wings more often, a mosquito or a bumblebee?

Sound timbre is a kind of sound color by which we distinguish the voices of people from different instruments. (slide 11).

Every complex musical sound consists of a number of simple harmonic sounds. The lowest one is the main one. The rest are higher than it by an integer number of times, for example, 2 or 3–4 times. They are called overtones. The more overtones mixed into the main tone, the richer the sound will be. High overtones add “shine” and “brightness” and “metallicity” to the timbre. Lows give “power” and “juiciness”. A.G. Stoletov wrote: “The simple tones that we get from our tuning forks are not used in music, they are as fresh and tasteless as distilled water.”

Consolidation

1. What is the name of the study of sound?
2. There was a strong explosion on the moon. For example, a volcanic eruption. Will we hear it on Earth?
3. Do the vocal cords vibrate at a lower frequency in a person singing bass or tenor?
4. Most insects make a sound when they fly. What caused it?
5. How could people communicate on the Moon?
6. Why are they tapped when checking carriage wheels during a train stop?

Homework:§34-38. Exercise 30 (No. 2, 3).

Literature

1. Physics course, Part II, for high school/Peryshkin A.V. – M.: Education, 1968. – 240 p.
2. Oscillations and waves in a physics course for high school. Manual for teachers/Orekhov V.P. – M.: Education, 1977. – 176 p.
3. Cricket behind the hearth/Dickens Ch. – M.: Eksmo, 2003. – 640 p.

Sound is caused by mechanical vibrations in elastic media and bodies, the frequencies of which lie in the range from 20 Hz to 20 kHz and which the human ear can perceive.

Accordingly, this mechanical vibration with the indicated frequencies is called sound and acoustic. Inaudible mechanical vibrations with frequencies below the sound range are called infrasonic, and with frequencies above the sound range they are called ultrasonic.

If a sounding body, for example an electric bell, is placed under the bell of an air pump, then as the air is pumped out the sound will become weaker and weaker and finally stop completely. The transmission of vibrations from the sounding body occurs through the air. Let us note that during its oscillations, the sounding body alternately compresses the air adjacent to the surface of the body, and, on the contrary, creates a vacuum in this layer. Thus, the propagation of sound in the air begins with fluctuations in air density at the surface of the vibrating body.

Musical tone. Volume and pitch

The sound that we hear when its source performs a harmonic oscillation is called musical tone or, for short, tone.

In any musical tone we can distinguish two qualities by ear: volume and pitch.

The simplest observations convince us that the tones of any given pitch are determined by the amplitude of the vibrations. The sound of a tuning fork gradually fades after striking it. This occurs together with the damping of oscillations, i.e. with a decrease in their amplitude. By hitting the tuning fork harder, i.e. By giving the vibrations a larger amplitude, we will hear a louder sound than with a weak blow. The same can be observed with a string and in general with any source of sound.

If we take several tuning forks of different sizes, it will not be difficult to arrange them by ear in order of increasing pitch. Thus, they will be arranged in size: the largest tuning fork gives the lowest sound, the smallest one gives the highest sound. Thus, the pitch of a tone is determined by the frequency of vibration. The higher the frequency and, therefore, the shorter the period of oscillation, the higher the sound we hear.

Acoustic resonance

Resonance phenomena can be observed in mechanical vibrations of any frequency, in particular in sound vibrations.

Let's place two identical tuning forks next to each other, with the holes of the boxes on which they are mounted facing each other. Boxes are needed because they amplify the sound of tuning forks. This occurs due to resonance between the tuning fork and the columns of air enclosed in the box; hence the boxes are called resonators or resonant boxes.

Let's hit one of the tuning forks and then muffle it with our fingers. We will hear how the second tuning fork sounds.

Let's take two different tuning forks, i.e. with different pitches, and repeat the experiment. Now each of the tuning forks will no longer respond to the sound of another tuning fork.

It is not difficult to explain this result. The vibrations of one tuning fork act through the air with some force on the second tuning fork, causing it to perform its forced vibrations. Since tuning fork 1 performs a harmonic oscillation, the force acting on tuning fork 2 will change according to the law of harmonic oscillation with the frequency of tuning fork 1. If the frequency of the force is different, then the forced oscillations will be so weak that we will not hear them.

Noises

We hear a musical sound (note) when the vibration is periodic. For example, this kind of sound is produced by a piano string. If you hit several keys at the same time, i.e. make several notes sound, then the sensation of musical sound will remain, but the difference between consonant (pleasant to the ear) and dissonant (unpleasant) notes will clearly appear. It turns out that those notes whose periods are in the ratio of small numbers are consonant. For example, consonance is obtained with a period ratio of 2:3 (fifth), 3:4 (quanta), 4:5 (major third), etc. If the periods are related as big numbers, for example 19:23, then the result is dissonance - a musical, but unpleasant sound. We will move even further away from the periodicity of oscillations if we hit many keys at the same time. The sound will already be noise-like.

Noise is characterized by a strong non-periodicity of the oscillation shape: either it is a long oscillation, but very complex in shape (hissing, creaking), or individual emissions (clicks, knocks). From this point of view, noises should also include sounds expressed by consonants (hissing, labial, etc.).

In all cases, noise vibrations consist of a huge number of harmonic vibrations with different frequencies.

Thus, the spectrum of a harmonic vibration consists of one single frequency. For a periodic oscillation, the spectrum consists of a set of frequencies - the main one and its multiples. In consonant consonances we have a spectrum consisting of several such sets of frequencies, with the main ones being related as small integers. In dissonant consonances, the fundamental frequencies are no longer in such simple relationships. The more different frequencies there are in the spectrum, the closer we come to noise. Typical noises have spectra in which there are extremely many frequencies.

With the help of this video lesson you can study the topic “Sound Sources. Sound vibrations. Pitch, timbre, volume." In this lesson you will learn what sound is. We will also consider the ranges of sound vibrations perceived by human hearing. Let's determine what can be the source of sound and what conditions are necessary for its occurrence. We will also study such sound characteristics as pitch, timbre and volume.

The topic of the lesson is devoted to sound sources and sound vibrations. We will also talk about the characteristics of sound - pitch, volume and timbre. Before talking about sound, about sound waves, let's remember that mechanical waves propagate in elastic media. The part of longitudinal mechanical waves that is perceived by the human hearing organs is called sound, sound waves. Sound is the mechanical waves perceived by the human hearing organs that cause sound sensations .

Experiments show that the human ear and human hearing organs perceive vibrations with frequencies from 16 Hz to 20,000 Hz. It is this range that we call sound. Of course, there are waves whose frequency is less than 16 Hz (infrasound) and more than 20,000 Hz (ultrasound). But this range, these sections are not perceived by the human ear.

Rice. 1. Hearing range of the human ear

As we said, the areas of infrasound and ultrasound are not perceived by the human hearing organs. Although they can be perceived, for example, by some animals and insects.

What's happened ? Sound sources can be any body that vibrates at a sound frequency (from 16 to 20,000 Hz)

Rice. 2. An oscillating ruler clamped in a vice can be a source of sound.

Let's turn to experience and see how a sound wave is formed. To do this we need a metal ruler, which we will clamp in a vice. Now, when we act on the ruler, we will be able to observe vibrations, but we will not hear any sound. And yet a mechanical wave is created around the ruler. Please note that when the ruler is moved to one side, an air seal is formed here. In the other direction there is also a seal. Air vacuum forms between these seals. Longitudinal wave - this is a sound wave consisting of compactions and rarefaction of air. Ruler oscillation frequency in in this case less than the sound frequency, so we don’t hear this wave, this sound. Based on the experience we have just observed, at the end of the 18th century, a device called a tuning fork was created.

Rice. 3. Propagation of longitudinal sound waves from a tuning fork

As we have seen, sound appears as a result of vibrations of a body with a sound frequency. Sound waves propagate in all directions. There must be a medium between the human hearing aid and the source of sound waves. This medium can be gaseous, liquid, or solid, but it must be particles capable of transmitting vibrations. The process of transmitting sound waves must necessarily occur where there is matter. If there is no substance, we will not hear any sound.

For sound to exist you need:

1. Sound source

2. Wednesday

3. Hearing aid

4. Frequency 16-20000Hz

5. Intensity

Now let's move on to discussing sound characteristics. The first is pitch. Sound height - characteristic that is determined by the frequency of oscillations. The higher the frequency of the body that produces vibrations, the higher the sound will be. Let's look again at the ruler held in a vice. As we have already said, we saw vibrations, but did not hear any sound. If we now make the length of the ruler shorter, we will hear the sound, but it will be much more difficult to see the vibrations. Look at the line. If we act on it now, we will not hear any sound, but we will observe vibrations. If we shorten the ruler, we will hear a sound of a certain pitch. We can make the length of the ruler even shorter, then we will hear a sound of even higher pitch (frequency). We can observe the same thing with tuning forks. If we take a large tuning fork (also called a demonstration fork) and hit the legs of such a tuning fork, we can observe the vibration, but we will not hear the sound. If we take another tuning fork, then when we hit it we will hear a certain sound. And the next tuning fork, a real tuning fork, which is used for tuning musical instruments. It makes a sound corresponding to the note A, or, as they also say, 440 Hz.

The next characteristic is the timbre of the sound. Timbre called sound color. How can this characteristic be illustrated? Timbre is the difference between two identical sounds performed by different musical instruments. You all know that we only have seven notes. If we hear the same note A played on a violin and on a piano, we can tell them apart. We can immediately tell which instrument created this sound. It is this feature - the color of the sound - that characterizes the timbre. It must be said that timbre depends on what sound vibrations are reproduced, in addition to the fundamental tone. The fact is that arbitrary sound vibrations are quite complex. They consist of a set of individual vibrations, they say vibration spectrum. It is the reproduction of additional vibrations (overtones) that characterizes the beauty of the sound of a particular voice or instrument. Timbre is one of the main and brightest manifestations of sound.

Another characteristic is volume. The volume of sound depends on the amplitude of vibrations. Let's take a look and make sure that loudness is related to the amplitude of vibrations. So, let's take a tuning fork. Let's do the following: if you hit the tuning fork weakly, the amplitude of vibrations will be small and the sound will be quiet. If you now hit the tuning fork harder, the sound will be much louder. This is due to the fact that the amplitude of the oscillations will be much greater. The perception of sound is a subjective thing, it depends on what kind of hearing aid is used and how a person feels.

List of additional literature:

Is the sound so familiar to you? // Quantum. - 1992. - No. 8. - P. 40-41. Kikoin A.K. ABOUT musical sounds and their sources // Quantum. - 1985. - No. 9. - P. 26-28. Elementary physics textbook. Ed. G.S. Landsberg. T. 3. - M., 1974.

Sound is sound waves that cause vibrations of tiny particles of air, other gases, and liquid and solid media. Sound can only arise where there is a substance, no matter what state of aggregation it is in. In vacuum conditions, where there is no medium, sound does not propagate, because there are no particles that act as distributors of sound waves. For example, in space. Sound can be modified, altered, turning into other forms of energy. Thus, sound converted into radio waves or electrical energy can be transmitted over distances and recorded on information media.

Sound wave

The movements of objects and bodies almost always cause fluctuations in the environment. It doesn't matter whether it's water or air. During this process, the particles of the medium to which the vibrations of the body are transmitted also begin to vibrate. Sound waves arise. Moreover, movements are carried out in forward and backward directions, progressively replacing each other. Therefore, the sound wave is longitudinal. There is never any lateral movement up and down in it.

Characteristics of sound waves

Like any physical phenomenon, they have their own quantities, with the help of which properties can be described. The main characteristics of a sound wave are its frequency and amplitude. The first value shows how many waves are formed per second. The second determines the strength of the wave. Low-frequency sounds have low frequency values, and vice versa. The frequency of sound is measured in Hertz, and if it exceeds 20,000 Hz, then ultrasound occurs. There are plenty of examples of low-frequency and high-frequency sounds in nature and the world around us. The chirping of a nightingale, the rumble of thunder, the roar of a mountain river and others are all different sound frequencies. The amplitude of the wave directly depends on how loud the sound is. The volume, in turn, decreases with distance from the sound source. Accordingly, the further the wave is from the epicenter, the smaller the amplitude. In other words, the amplitude of a sound wave decreases with distance from the sound source.

Sound speed

This indicator of a sound wave is directly dependent on the nature of the medium in which it propagates. Both humidity and air temperature play a significant role here. In average weather conditions, the speed of sound is approximately 340 meters per second. In physics, there is such a thing as supersonic speed, which is always greater than the speed of sound. This is the speed at which sound waves travel when an aircraft moves. The plane moves at supersonic speed and even outruns the sound waves it creates. Due to the pressure gradually increasing behind the aircraft, a shock wave of sound is formed. The unit of measurement for this speed is interesting and few people know it. It's called Mach. Mach 1 is equal to the speed of sound. If a wave travels at Mach 2, then it travels twice as fast as the speed of sound.

Noises

There is constant noise in human daily life. The noise level is measured in decibels. The movement of cars, the wind, the rustling of leaves, the interweaving of people's voices and other sound noises are our daily companions. But to such noises auditory analyzer a person has the ability to get used to it. However, there are also phenomena that even the adaptive abilities of the human ear cannot cope with. For example, noise exceeding 120 dB can cause pain. The loudest animal is the blue whale. When it makes sounds, it can be heard over 800 kilometers away.

Echo

How does an echo occur? Everything is very simple here. A sound wave has the ability to be reflected from different surfaces: from water, from a rock, from walls in an empty room. This wave returns to us, so we hear secondary sound. It is not as clear as the original one because some of the energy in the sound wave is dissipated as it travels toward the obstacle.

Echolocation

Sound reflection is used for various practical purposes. For example, echolocation. It is based on the fact that with the help of ultrasonic waves it is possible to determine the distance to the object from which these waves are reflected. Calculations are made by measuring the time it takes for ultrasound to travel to a location and return. Many animals have the ability to echolocation. For example, bats and dolphins use it to search for food. Echolocation has found another application in medicine. When examining with ultrasound, a picture is formed internal organs person. The basis of this method is that ultrasound, entering a medium other than air, returns back, thus forming an image.

Sound waves in music

Why do musical instruments make certain sounds? Guitar strumming, piano strumming, low tones of drums and trumpets, the charming thin voice of a flute. All these and many other sounds arise due to air vibrations or, in other words, due to the appearance of sound waves. But why is the sound of musical instruments so diverse? It turns out that this depends on several factors. The first is the shape of the tool, the second is the material from which it is made.

Let's look at this using string instruments as an example. They become a source of sound when the strings are touched. As a result, they begin to oscillate and send environment different sounds. The low sound of any stringed instrument is due to the greater thickness and length of the string, as well as the weakness of its tension. And vice versa, the more tightly the string is stretched, the thinner and shorter it is, the higher the sound obtained as a result of playing.

Microphone action

It is based on the conversion of sound wave energy into electrical energy. In this case, the current strength and the nature of the sound are directly dependent. Inside any microphone there is a thin plate made of metal. When exposed to sound, it begins to perform oscillatory movements. The spiral to which the plate is connected also vibrates, resulting in electricity. Why does he appear? This is because the microphone also has built-in magnets. When the spiral oscillates between its poles, an electric current is generated, which goes along the spiral and then to a sound column (loudspeaker) or to equipment for recording on an information medium (cassette, disk, computer). By the way, the microphone in the phone has a similar structure. But how do microphones work on landline and mobile phone? The initial phase is the same for them - sound human voice transmits its vibrations to the microphone plate, then everything follows the scenario described above: a spiral, which, when moving, closes two poles, a current is created. What's next? With a landline telephone, everything is more or less clear - just like in a microphone, the sound, converted into electric current, runs through the wires. But what about a cell phone or, for example, a walkie-talkie? In these cases, the sound is converted into radio wave energy and hits the satellite. That's all.

Resonance phenomenon

Sometimes conditions are created when the amplitude of oscillations physical body increases sharply. This occurs due to the convergence of the values ​​of the frequency of forced oscillations and the natural frequency of oscillations of the object (body). Resonance can be both beneficial and harmful. For example, to get a car out of a hole, it is started and pushed back and forth in order to cause resonance and give the car inertia. But there were also cases negative consequences resonance. For example, in St. Petersburg, about a hundred years ago, a bridge collapsed under soldiers marching in unison.