Otitis

Sound is sound vibrations. Sound vibrations

A sound wave (sound vibrations) is a mechanical vibration of molecules of a substance (for example, air) transmitted in space.

But not every oscillating body is a source of sound. For example, an oscillating weight suspended on a thread or spring does not make a sound. A metal ruler will also stop sounding if you move it upward in a vice and thereby lengthen the free end so that its vibration frequency becomes less than 20 Hz. Research has shown that the human ear is capable of perceiving as sound mechanical vibrations of bodies occurring at a frequency from 20 Hz to 20,000 Hz. Therefore, vibrations whose frequencies are in this range are called sound. Mechanical vibrations whose frequency exceeds 20,000 Hz are called ultrasonic, and vibrations with frequencies less than 20 Hz are called infrasonic. It should be noted that the indicated boundaries of the sound range are arbitrary, since they depend on the age of people and individual characteristics their hearing aid. Typically, with age, the upper frequency limit of perceived sounds decreases significantly - some older people can hear sounds with frequencies not exceeding 6000 Hz. Children, on the contrary, can perceive sounds whose frequency is slightly higher than 20,000 Hz. Vibrations with frequencies greater than 20,000 Hz or less than 20 Hz are heard by some animals. The world is filled with a wide variety of sounds: the ticking of clocks and the hum of engines, the rustling of leaves and the howling of the wind, the singing of birds and the voices of people. People began to guess about how sounds are born and what they are a very long time ago. They noticed, for example, that sound is created by bodies vibrating in the air. Even the ancient Greek philosopher and encyclopedist Aristotle, based on observations, correctly explained the nature of sound, believing that a sounding body creates alternating compression and rarefaction of air. Thus, an oscillating string either compresses or rarefies the air, and thanks to the elasticity of the air, these alternating effects are transmitted further into space - from layer to layer, elastic waves arise. Reaching our ear, they affect eardrums and cause the sensation of sound. By ear, a person perceives elastic waves with a frequency ranging from approximately 16 Hz to 20 kHz (1 Hz - 1 vibration per second). In accordance with this, elastic waves in any medium, the frequencies of which lie within the specified limits, are called sound waves or simply sound. In air at a temperature of 0° C and normal pressure sound travels at a speed of 330 m/s, in sea water- about 1500 m/s, in some metals the speed of sound reaches 7000 m/s. Elastic waves with a frequency of less than 16 Hz are called infrasound, and waves whose frequency exceeds 20 kHz are called ultrasound.

The source of sound in gases and liquids can be not only vibrating bodies. For example, a bullet and an arrow whistle in flight, the wind howls. And the roar of a turbojet aircraft consists not only of the noise of operating units - fan, compressor, turbine, combustion chamber, etc., but also of the noise of the jet stream, vortex, turbulent air flows that occur when flowing around the aircraft at high speeds. A body rushing rapidly through the air or water seems to break the flow flowing around it and periodically generates regions of rarefaction and compression in the medium. As a result, sound waves are generated. Sound can travel in the form of longitudinal and transverse waves. In gaseous and liquid medium Only longitudinal waves arise when the oscillatory motion of particles occurs only in the direction in which the wave propagates. In solids, in addition to longitudinal waves, transverse waves also arise when particles of the medium vibrate in directions perpendicular to the direction of propagation of the wave. There, striking the string perpendicular to its direction, we force a wave to run along the string. The human ear is not equally sensitive to sound different frequencies. It is most sensitive to frequencies from 1000 to 4000 Hz. At very high intensity, the waves are no longer perceived as sound, causing a sensation in the ears pressing pain. The intensity of sound waves at which this occurs is called the threshold pain. The concepts of tone and timbre of sound are also important in the study of sound. Any real sound, be it a human voice or the playing of a musical instrument, is not a simple harmonic vibration, but a peculiar mixture of many harmonic vibrations with a certain set of frequencies. The one that has the most low frequency, are called the fundamental tone, others - overtones. The different number of overtones inherent in a particular sound gives it a special coloring - timbre. The difference between one timbre and another is determined not only by the number, but also by the intensity of the overtones accompanying the sound of the main tone. By timbre, we easily distinguish the sounds of a violin and a piano, a guitar and a flute, and recognize the voices of familiar people.

Oscillation frequency called the number of complete oscillations per second. The unit of frequency measurement is 1 hertz (Hz). 1 hertz corresponds to one complete (in one direction or the other) oscillation, occurring in one second.
Period is the time (s) during which one complete oscillation occurs. The higher the frequency of oscillations, the shorter their period, i.e. f=1/T. Thus, the frequency of oscillations is greater, the shorter their period, and vice versa. The human voice creates sound vibrations with a frequency of 80 to 12,000 Hz, and the ear perceives sound vibrations in the range of 16-20,000 Hz.
Amplitude oscillations are the greatest deviation of an oscillating body from its original (quiet) position. The greater the amplitude of the vibration, the louder the sound. The sounds of human speech are complex sound vibrations, consisting of one or another number of simple vibrations, varying in frequency and amplitude. Each speech sound has its own unique combination of vibrations of different frequencies and amplitudes. Therefore, the shape of vibrations of one speech sound is noticeably different from the shape of another, which shows graphs of vibrations during the pronunciation of the sounds a, o and y.

A person characterizes any sounds in accordance with his perception by volume level and pitch.

Before you understand what sound sources there are, think about what sound is? We know that light is radiation. Reflecting from objects, this radiation reaches our eyes, and we can see it. Taste and smell are small particles of bodies that are perceived by our respective receptors. What kind of animal is this sound?

Sounds are transmitted through the air

You've probably seen how the guitar is played. Perhaps you can do this yourself. Another important thing is the sound the strings make in a guitar when you pluck them. That's right. But if you could place a guitar in a vacuum and pluck the strings, you would be very surprised that the guitar would not make any sound.

Such experiments were carried out with a wide variety of bodies, and the result was always the same: no sound could be heard in airless space. The logical conclusion follows that sound is transmitted through the air. Therefore, sound is something that happens to particles of air and sound-producing bodies.

Sources of sound - oscillating bodies

Next. As a result of a wide variety of numerous experiments, it was possible to establish that sound arises due to the vibration of bodies. Sources of sound are bodies that vibrate. These vibrations are transmitted by air molecules and our ear, perceiving these vibrations, interprets them into sensations of sound that we understand.

It's not difficult to check. Take a glass or crystal goblet and place it on the table. Tap it lightly with a metal spoon. You will hear a long thin sound. Now touch the glass with your hand and knock again. The sound will change and become much shorter.

Now let several people wrap their hands around the glass as completely as possible, along with the stem, trying not to leave a single free area, except completely small place for hitting with a spoon. Hit the glass again. You will hardly hear any sound, and the one that will be will be weak and very short. What does this mean?

In the first case, after the impact, the glass oscillated freely, its vibrations were transmitted through the air and reached our ears. In the second case, most of the vibrations were absorbed by our hand, and the sound became much shorter as the vibrations of the body decreased. In the third case, almost all vibrations of the body were instantly absorbed by the hands of all participants and the body hardly vibrated, and therefore made almost no sound.

The same goes for all other experiments you can think of and conduct. Vibrations of bodies, transmitted to air molecules, will be perceived by our ears and interpreted by the brain.

Sound vibrations of different frequencies

So sound is vibration. Sound sources transmit sound vibrations through the air to us. Why then do we not hear all the vibrations of all objects? Because vibrations come in different frequencies.

Perceived human ear sound is sound vibrations with a frequency of approximately 16 Hz to 20 kHz. Children hear sounds of higher frequencies than adults, and the ranges of perception of different living creatures generally vary greatly.

Ears are a very thin and delicate instrument, given to us by nature, so we should take care of it, since replacements and analogues are in human body does not exist.

Sound sources. Sound vibrations

Man lives in a world of sounds. Sound for humans is a source of information. He warns people about danger. Sound in the form of music, birdsong gives us pleasure. We enjoy listening to a person with a pleasant voice. Sounds are important not only for humans, but also for animals, for which good sound detection helps them survive.

Sound – these are mechanical elastic waves propagating in gases, liquids, and solids.

Reason for the sound - vibration (oscillations) of bodies, although these vibrations are often invisible to our eyes.

Sound sources - physical bodies, which fluctuate, i.e. tremble or vibrate at a frequency
from 16 to 20,000 times per second. The vibrating body can be solid, for example, a string
or earth's crust, gaseous, for example, a stream of air in wind musical instruments
or liquid, for example, waves on water.

Volume

The volume depends on the amplitude of vibrations in sound wave. The unit of sound volume is 1 Bel (in honor of Alexander Graham Bell, the inventor of the telephone). In practice, loudness is measured in decibels (dB). 1 dB = 0.1B.

10 dB – whisper;

20–30 dB – noise standards in residential premises;
50 dB– medium volume conversation;
80 d B – the noise of a running truck engine;
130 dB– pain threshold

Sound louder than 180 dB can even cause eardrum rupture.

High sounds represented by high-frequency waves - for example, birdsong.

Low sounds These are low-frequency waves, such as the sound of a large truck engine.

Sound waves

Sound waves- These are elastic waves that cause a person to feel the sensation of sound.

A sound wave can travel a wide variety of distances. Gunfire can be heard at 10-15 km, the neighing of horses and barking dogs - at 2-3 km, and whispers only at a few meters. These sounds are transmitted through the air. But not only air can be a conductor of sound.

By placing your ear to the rails, you can hear the sound of an approaching train much earlier and at a greater distance. This means that metal conducts sound faster and better than air. Water also conducts sound well. Having dived into the water, you can clearly hear the stones knocking against each other, the noise of the pebbles during the surf.

The property of water - it conducts sound well - is widely used for reconnaissance at sea during war, as well as for measuring sea depths.

A necessary condition for the propagation of sound waves is the presence of a material medium. In a vacuum, sound waves do not propagate, since there are no particles there that transmit the interaction from the source of vibration.

Therefore, due to the lack of atmosphere, complete silence reigns on the Moon. Even the fall of a meteorite on its surface is not audible to the observer.

In each medium, sound travels at different speeds.

Speed of sound in air- approximately 340 m/s.

Speed of sound in water- 1500 m/s.

Speed of sound in metals, steel- 5000 m/s.

In warm air, the speed of sound is greater than in cold air, which leads to a change in the direction of sound propagation.

FORK

- This U-shaped metal plate, the ends of which can vibrate after being struck.

Published tuning fork the sound is very weak and can only be heard at a short distance.
Resonator- a wooden box on which a tuning fork can be attached serves to amplify the sound.
In this case, sound emission occurs not only from the tuning fork, but also from the surface of the resonator.
However, the duration of the sound of a tuning fork on a resonator will be shorter than without it.

E X O

A loud sound, reflected from obstacles, returns to the source of sound after a few moments, and we hear echo.

By multiplying the speed of sound by the time elapsed from its origin to its return, you can determine twice the distance from the sound source to the obstacle.
This method of determining the distance to objects is used in echolocation.

Some animals, for example bats,
also use the phenomenon of sound reflection using the echolocation method

Echolocation is based on the property of sound reflection.

Sound - running mechanical wave on and transfers energy.
However, the power of simultaneous conversation of all people on the globe is hardly more than the power of one Moskvich car!

Ultrasound.

· Vibrations with frequencies exceeding 20,000 Hz are called ultrasound. Ultrasound is widely used in science and technology.

· The liquid boils when an ultrasonic wave passes through (cavitation). In this case, water hammer occurs. Ultrasounds can tear pieces off the surface of metal and crush solids. Ultrasound can be used to mix immiscible liquids. This is how emulsions in oil are prepared. Under the influence of ultrasound, saponification of fats occurs. Washing devices are designed on this principle.

Widely used ultrasound in hydroacoustics. Ultrasounds of high frequency are absorbed very weakly by water and can spread over tens of kilometers. If they meet the bottom, iceberg or other solid, they are reflected and give an echo of great power. An ultrasonic echo sounder is designed on this principle.

In metal ultrasound spreads practically without absorption. Using the ultrasonic location method, it is possible to detect the smallest defects inside a part of large thickness.

· The crushing effect of ultrasound is used for the manufacture of ultrasonic soldering irons.

Ultrasonic waves, sent from the ship, are reflected from the sunken object. The computer detects the time the echo appears and determines the location of the object.

· Ultrasound is used in medicine and biology for echolocation, for identifying and treating tumors and some defects in body tissues, in surgery and traumatology for dissecting soft and bone tissues during various operations, for welding broken bones, for destroying cells (high power ultrasound).

Infrasound and its impact on humans.

Vibrations with frequencies below 16 Hz are called infrasound.

In nature, infrasound occurs due to the vortex movement of air in the atmosphere or as a result of slow vibrations of various bodies. Infrasound is characterized by weak absorption. Therefore, it spreads over long distances. The human body reacts painfully to infrasonic vibrations. At external influences caused by mechanical vibration or sound wave at frequencies of 4-8 Hz, a person feels movement internal organs, at a frequency of 12 Hz - an attack of seasickness.

· Highest intensity infrasonic vibrations create machines and mechanisms that have surfaces large sizes, performing low-frequency mechanical vibrations (infrasound of mechanical origin) or turbulent flows of gases and liquids (infrasound of aerodynamic or hydrodynamic origin).

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 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 huge amount 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.

Objective 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 own experience V 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.

Lesson progress

Among the various oscillatory and wave movements found in nature and technology, especially important in human life there are sound vibrations and waves, and just sounds. 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. Due to the presence of a hearing organ in a person, he receives from environment with the help of sounds, large and varied information. 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 to his feet again. 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 makes harmonic vibrations )

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 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. So on your ears man is walking an impact equal to that exerted on 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. Auditory system ceases to perceive high frequencies."Any noise with an intensity of more than 80 decibels negatively affects inner ear, says Candidate of 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 responsible for transmission die in our ears. sound signal into the brain. 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 equal to 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 a room from intrusion extraneous sounds, 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 a loud sound.

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

What is the name of the study of sound?
happened on the moon strong explosion. For example, a volcanic eruption. Will we hear it on Earth?
Vocal cords oscillate at a lower frequency in a person singing bass or tenor?
Most insects make a sound when they fly. What caused it?
How could people communicate on the Moon?
Why are they tapped when checking carriage wheels during a train stop?

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

Literature

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