The theory of sound and acoustics in an understandable language.

Physical quantities:

λ = vT= v / γ(m) wavelength

v = λ/ T = λ γ (m/s) wave speed

T \u003d t / n (c) oscillation period

n - number of oscillations t - oscillation time

γ \u003d 1 / T (Hz) oscillation frequency A [m] - oscillation amplitude

I. 1. Greeting, checking the readiness of students for the lesson, readiness visual aids, blackboard, chalk, etc.

2. Disclosure of the general purpose of the lesson.

Today we have the opportunity to touch the world of beauty and harmony, which is present in one of the species. uneven movement- oscillatory. Vibrational movements are widespread in the life around us. Sound is one of the types of oscillatory movement, a means of transmitting information, approximately 8-9% of the total volume received by a person.

An introductory generalization and systematization of knowledge about oscillations and waves will allow us to move on to the study of sound phenomena from the standpoint of integration with other sciences.

So, the purpose of our lesson is to generalize and systematize knowledge about sound vibrations, their characteristics and familiarity with the use of sound waves in various fields of science, technology, art, nature. Therefore, I present the topic of the lesson: "Sound in nature, music and technology".

II. Updating of basic knowledge and skills. Formation of cognitive motives.

First independent task there will be work with a reference abstract, which contains the most important information about oscillations and waves. Focus on key concepts

· Independent work on repetition and consolidation of the section "Oscillations and waves".

Systematization of basic concepts, physical quantities characterizing wave process.

Find answers to questions in the reference notes:

1. Give examples of oscillatory movements.

2. What is the main feature of oscillatory motion?

3. What is the oscillation period? Oscillation frequency? Oscillation amplitude?

4. Write down the formulas of physical quantities and indicate their units of measurement.

5. If the graph of the dependence of the coordinate on time is a sinusoid (cosine wave) - what kind of oscillations does the body make?

6. Disturbances propagating in space are called...?

7. In what media is it possible for elastic waves to propagate?

8. Write down the formulas for the wavelength, wave propagation velocity

() and specify their units of measurement.

9. a brief description of sound waves: starting from the concepts of mechanical vibrations and waves, let's move on to sound waves.

	Frequencies of sound waves perceived by the human ear
	The pitch is determined	Pitch Depends on the frequency you hesitate pitch
	Fundamental frequency (fundamental tone)	The lowest frequency of a complex sound.
	Overtones (higher harmonic tones)	The frequencies of all overtones of a given sound are an integer number of times greater than the frequency of the fundamental tone. Overtones determine the timbre of the sound, its quality.
	Sound timbre	Determined by the totality of its overtones.
	Sound volume is determined	It is determined by the amplitude of oscillations. In practical tasks, it is characterized by the loudness level (the unit of measurement is phons, whites (decibels).
	Sound interference	The phenomenon of addition in the space of waves, in which a time-constant distribution of the amplitudes of the resulting oscillations is formed.
	physical waves characterizing the sound wave	Wavelength: λ Sound speed: V Sound speed in air: V = 340 m/s

III. Control and self-examination of knowledge (reflection) of intercourse concepts.

Having repeated the theoretical material, let's move on to a practical task to identify some properties of sound waves.

1. Practical task (group work):

a) the first group performs an experiment on sound reflection with two cymbals and a barrel organ.

Task number 1. Using the "hurdy-gurdy" to investigate the property of reflection of sound waves. Get the sound coming from a cymbal leaning against your ear.

Conclusion: sound bouncing off objects .

b) the second group checks the main characteristics of the sound: pitch and loudness.

Task number 2. Find out on what physical quantities the pitch and loudness of the sound depend on using a ruler fixed on the table, changing the length of its protruding part and the amplitude of the oscillations. When does the sound become audible, not audible?

Conclusion : by changing the length of the protruding part of the ruler and the amplitude of its oscillations, it is found out that the pitch of the tone emitted by the oscillating ruler depends on its size, and the volume is determined by the amplitude of the oscillations.

c) the third group is experimenting with a spoon, testing the propagation of sound in various environments using a stethoscope.

Task number 3. Put the ear tubes of the stethoscope probe into your ears. Hit a metal spoon with a hammer. Make a conclusion and achieve the sound of the "bell". What does it say?

Conclusion: Sound travels not only in air, but also in liquids and solids.

d) make a wind instrument;

Task number 4. Get a simple wind instrument from the lid of a resonator box and three test tubes.

e) get a pure tone with a tuning fork and make the sound visible;

Task number 5. Get a clean, musical tone with a tuning fork. Make this sound visible.

g) individual work with handouts (oral responses of students).

Questions:

1. When flying, most insects make a sound. What is it called?

2. Large rain can be distinguished from small rain by a louder sound that occurs when the drops hit the roof. What is this possibility based on?

3. Do loud and quiet sounds have the same wavelengths of sound waves in the same medium?

4. Which insect - a mosquito or a fly - does large quantity flapping wings in the same amount of time?

5. Why, if we want to be heard at a great distance, do we scream and at the same time put our hands folded like a mouthpiece to our mouth?

6. String musical instrument has from 3 to 7 strings. How is the variety of sounds produced by the instrument achieved?

Conclusion: Sound waves form circular waves on the surface of the water.

IV. Generalization and systematization of knowledge about sound waves based on the integration of the sciences of physics, biology, ecology, music.

Physics as a science is a cultural achievement that gives us a uniquely powerful way of understanding the world. Only one of the types of mechanical vibrations - sound waves - gives a whole range of interesting facts of applied significance. Sounds are intangible, invisible, but let's become magicians for a moment and materialize them.

· Physical properties sound waves.

1. The scale of the range of sound waves.

2. Table of the speed of sound in various substances, a graph of the speed of sound in air at various temperatures and the dependence of the speed of sound on height above the Earth's surface.

3. Doppler effect in acoustics.

A drawing showing the change in pitch. Solving a problem situation (an observer emitting a sound wave + a body flying past + what is the result of changing the frequency. What effect will be observed?

4. Experiment with sound waves.

· engineering application of the properties of sound.

1. Hall acoustics.

The hall of the Bolshoi Theater is compared to a large violin, now its wooden shell is being restored to improve acoustics.

· Musical instruments.

1. Piano.

Pollutions are different: nature, soul, informational. Do punk, metal, trance, techno music styles belong to noise pollution?

Problem task: Highlight the positive and negative aspects of musical works of the style: "punk", "metal", "trance", "techno".

· Biology. The meaning of sounds in animal life.

1. Pisces are incredibly talkative.

Question . Leonardo da Vinci suggested listening to underwater sounds by putting your ear to an oar lowered into the water. The acoustic impedance of raw wood is close to that of water. Why?

· Ecology and ultrasound.

1. "Sensation" in a basin of water.

· Ultrasound in medicine.

· acoustic pollution.

TOTAL. The information you have received will hopefully enrich your knowledge of sound waves.

V. Summarizing.

.New terms:

* generation (creation, education);

* reverberation (residual sound);

* acoustic impedance (the product of the density of a substance and the speed of propagation of a sound wave in it);

* echolocation (the ability to perceive an echo);

* sonars (devices for emitting and receiving echo signals);

* piano (from it. forte - "loud", piano - "quiet");

* essay (a kind of essay in which thoughts play the main role).

And now let's make a conclusion about the significance and place of acoustics (the science of sound waves) in the system of oscillatory processes. What useful information did we learn from the lesson?

Withdrawal of students:

a) the scope of sound is extensive, the sound is multifaceted

b) we generalized and systematized knowledge about sound phenomena.

c) got acquainted with the integration of the physical phenomenon of sound vibrations with the sciences of engineering, biology, ecology, music.

Teacher's conclusion:

I thank you for your cooperation, communication, striving for self-improvement, learning new things, the ability to analyze, generalize. I would especially like to highlight the following students...

VI. Homework. Essay: "My understanding of acoustics and its use in science and technology."

I propose to complete the task, in which there will be information that was not heard in today's lesson.

BACKGROUND SUMMARY.

Mechanical oscillations and waves. Sound.

1. One of the types of uneven movement is oscillatory. Vibrational movements are widespread in the life around us. Examples of oscillations are: the movement of the needle of a sewing machine, swings, clock pendulums, a wagon on springs and other bodies. The figure shows the bodies making oscillating motion, if they are taken out of equilibrium:

2. After a certain period of time, the movement of any body is repeated. The time interval after which the movement repeats is called period of oscillation. T=t/n[c] t - oscillation time; n is the number of oscillations for this period of time. 3. The number of oscillations per unit time is called frequency oscillations, denoted by the letter V ("nu"), measured in hertz [Hz]. [Hz].

4. The greatest (modulo) deviation of an oscillating body from the equilibrium position is called amplitude fluctuations.

OA1 and OB1 - oscillation amplitude (A); OA1=OB1=A [m]

5. In nature and technology, fluctuations are widespread, called harmonic.

Harmonic vibrations are those that occur under the action of a force proportional to the displacement of the oscillating point and directed opposite to this displacement.

The graph of the dependence of the coordinate of an oscillating body on time is a sinusoid (cosine wave).

https://pandia.ru/text/78/333/images/image005_14.gif" width="13" height="15"> half-waves of transverse standing waves. The oscillation mode corresponding to is called the first harmonic of natural oscillation waves or the fundamental mode .

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LESSON ANALYSIS.

1. Lesson type: complex application of knowledge, skills and abilities .

The lesson is problematic, interactive, based on complex application knowledge and skills, is of practical importance, since experimental facts are used that contribute to an independent assessment of these scientific discoveries.

The purpose of the lesson : to form in students the ability to apply theoretical knowledge and experimental scientific facts to understand the nature of light, the role, place and various methods determining its speed.

2. I consider the organization of the lesson to be the most optimal, because it allowed us to consider the problem of the nature of light comprehensively and made it possible to realize creativity when searching for the speed of light, use complex knowledge, skills and abilities.

3. To activate the attention of students, I selected methods of intra-subject and intersubject communications based on the knowledge of astronomy, the history of physical discoveries, the continuity of physical science, engineering discoveries.

Content absorption educational material, in my opinion, was provided through comprehension and consolidation theoretical material. The task was not only to ensure the assimilation of the material, but the main attention was paid to reproductive application in the course of practical work on self-assessment of the speed of light and creative thinking of students.

4. In my opinion, within didactic purpose lessons have been implemented:

* in the cognitive aspect:

An attempt was made to expand the scientific worldview against the background of the educational task;

* in the developmental aspect:

Enriched and complicated vocabulary;

Thinking skills are stimulated, such as comparison, analysis, synthesis, the ability to highlight the main thing, proof and refutation;

* in the educational aspect:

The emphasis is on the significance of the continuity of physical science, its most important laws and theories, and ways to confirm their reliability.

A differentiated approach is provided, taking into account the fact that the lesson was held in an unfamiliar class. The work was built on individual assignments as well as in team work. Students were involved in the process of identifying the cause-and-effect relationships of phenomena and facts. In my opinion, the applied methods of mutual control and self-control on the part of students are justified, there was an increase in the degree of independence in the system of tasks.

I think that a positive psychological climate was created at the lesson. The material was perceived with interest, because it is innovative and is not presented in the school textbook (grade 11). I believe that the level of students made it possible to ensure the quality of the acquired knowledge.

The pitch depends on how often the sound sources vibrate. The higher the oscillation frequency, the louder the sound. The simplest type of vibration is harmonic vibration. A pure tone is the sound of a tuning fork.

pure tone is a sound that makes harmonic vibrations of the same frequency. In musical tone, two qualities can be distinguished by sound - loudness and pitch.

Sounds different sources(for example, different musical instruments, the human voice, the sounds of foreign objects, etc.) together constitute a set harmonic vibrations different frequencies.

The fundamental frequency is the smallest frequency of this multi-component sound, and the sound that corresponds to it and is of a certain height is called the fundamental tone.

Overtones all other components of this multi-component sound are called (its frequency can be several times greater than the frequency of the fundamental tone).

Overtones define timbre sound is what allows us to distinguish sounds, for example, we can very easily distinguish the sound of a TV and washing machine, guitar and drum sounds, etc.

Sound pitch is also measured in melach- This is a pitch scale that allows you to set the equality of the pitches of two sounds.

Shepard's tone (acoustic illusions) is a sound with an apparent rising and falling pitch.

The pitch of a sound is determined by the frequency of its fundamental tone, if the frequency of the fundamental tone is higher, then the sound is louder, if the frequency of the fundamental tone is lower, then the sound will be quieter.

Sound volume

Sound volume- the quality of the auditory sensation, which allows you to place all sounds on a scale from quiet to loud.

Sleep is a unit of sound volume.

1 sone is the approximate volume of a muffled conversation, and the volume of an airplane is 264 sone. Sounds that are even louder will cause pain.

The loudness of the sound depends on the amplitude of the vibrations, the larger it is, the louder the sound will be.

The sound pressure level is measured in bels (B) or decibels (D) - 1/10 of a bela (B), and is equal to the sound volume level, which is expressed in phons.

Loudness above 180 dB can cause eardrum rupture.

Noise, loud sound, unpleasant sound have a bad effect on human health; this is due to the fact that the order of sounds of different loudness, pitch and timbre is disturbed.

Noise- These are sounds in which there are vibrations of various frequencies.

To have a sound sensation sound wave should be of minimum intensity, but if the intensity exceeds the norm, then the sound will not be heard and will only cause pain.

Acoustics is a branch of physics that studies sound phenomena.

Sounds are of two types: natural and artificial.

Sound waves, like other waves, are characterized by such objective quantities as frequency, amplitude, phase of oscillations, propagation velocity, sound intensity, and others. But. in addition, they are described by three subjective characteristics. These are sound volume, pitch and timbre.

The sensitivity of the human ear is different for different frequencies. In order to cause a sound sensation, the wave must have a certain minimum intensity, but if this intensity exceeds a certain limit, then the sound is not heard and only causes pain. Thus, for each oscillation frequency, there is the smallest (threshold of hearing) and the greatest (threshold pain sensation) the intensity of a sound that is capable of producing a sound sensation. Figure 15.10 shows the dependence of hearing and pain thresholds on sound frequency. The area between these two curves is hearing area. The greatest distance between the curves falls on the frequencies to which the ear is most sensitive (1000-5000 Hz).

If the intensity of sound is a quantity that objectively characterizes the wave process, then the subjective characteristic of sound is the loudness. Loudness depends on the intensity of the sound, i.e. determined by the square of the amplitude of oscillations in the sound wave and the sensitivity of the ear (physiological features). Since the intensity of the sound is \(~I \sim A^2,\), the greater the amplitude of the oscillations, the louder the sound.

Pitch- sound quality, determined by a person subjectively by ear and depending on the frequency of the sound. The higher the frequency, the higher the tone of the sound.

Sound vibrations occurring according to the harmonic law, with a certain frequency, are perceived by a person as a certain musical tone. High frequency vibrations are perceived as sounds high tone, low frequency sounds - like sounds low tone. The range of sound vibrations corresponding to a change in the frequency of vibrations by a factor of two is called octave. So, for example, the tone "la" of the first octave corresponds to a frequency of 440 Hz, the tone "la" of the second octave corresponds to a frequency of 880 Hz.

Musical sounds correspond to sounds emitted by a harmoniously vibrating body.

Main tone A complex musical sound is called a tone corresponding to the lowest frequency that exists in the set of frequencies of a given sound. Tones corresponding to other frequencies in the composition of the sound are called overtones. If the frequencies of the overtones are multiples of the frequency \(~\nu_0\) of the fundamental tone, then the overtones are called harmonic, and the fundamental tone with a frequency \(~\nu_0\) is called the first harmonic overtone with the following frequency \(~2 \nu_0\) - second harmonic etc.

Musical sounds with the same fundamental tone differ in timbre, which is determined by the presence of overtones - their frequencies and amplitudes, the nature of the increase in amplitudes at the beginning of the sound and their decline at the end of the sound.

At the same pitch, sounds made, for example, by a violin and a piano, differ timbre.

The perception of sound by the hearing organs depends on what frequencies are included in the sound wave.

Noises- these are sounds that form a continuous spectrum, consisting of a set of frequencies, i.e. Noise contains fluctuations of various frequencies.

Literature

Aksenovich L. A. Physics in high school: Theory. Tasks. Tests: Proc. allowance for institutions providing general. environments, education / L. A. Aksenovich, N. N. Rakina, K. S. Farino; Ed. K. S. Farino. - Mn.: Adukatsia i vykhavanne, 2004. - S. 431-432.

Task number 1 Using the "hurdy-gurdy" to investigate the property of reflection of sound waves. Get the sound coming from a cymbal leaning against your ear. Task number 2 Find out on what physical quantities the pitch and loudness of sound depend on using a ruler fixed on the table, changing the length of its protruding part and the amplitude of vibrations. When does the sound become audible, not audible? Task number 3 Put the ear tubes of the stethoscope probe in your ears. Hit a metal spoon with a hammer. Get the "bell" sound. Conclude what it says? Task #4 Get a clean, musical tone with a tuning fork. Make this sound visible. Task number 5 Get the simplest wind instrument from the lid of the resonator box and three test tubes.

Picture 11 from the presentation "Properties of sound" to physics lessons on the topic "Sound"

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Sound

"Sound vibrations" - Propagation and receivers of sound. It spreads in any elastic medium: solid; liquid; gaseous. Experiment #3 Infrasound - vibrations occurring at a frequency of less than 20 Hz. Research of characteristics of sound waves by means of PC. Optics. Experiment #1 Loudness - Depends on the amplitude of the vibrating medium.

"Sound sound vibrations" - Acoustic sound. Key words of the lesson. (Right). Artificial. Audible (acoustic). 3. Ultrasound is the language of animal communication: dolphin, bats. But cats, emitted by infrasound, are able to treat a person with a purr. Dolphin. Causes of sound. In air under normal conditions, the speed of sound is 330 m/s.

"Properties of sound" - A stringed musical instrument has from 3 to 7 strings. Sensation in a basin of water. Solving a problem situation. We generalized and systematized knowledge about sound phenomena. Ultrasound in medicine. An observer emitting a sound wave; passing body. Practical task. Task number 3 Put the ear tubes of the stethoscope probe in your ears.

"Reflection of sound" - 1. What is the speed of sound in air? Reflection of sound. Test on the topic “Sound. 3. The sound wave in the air is: 6. The action of the horn is based on the property of sound: 4. The echo is formed as a result of: 2. How does the speed of sound change when the density of the medium decreases?

"The speed of sound in various media" - What do reference books say? Experiment. Our tasks: Write down the formula by which the speed of sound is calculated. How does the speed of sound depend on the medium? Dip in a vessel of water wristwatches and place the ear at some distance. The best audibility at a cardboard tilt angle of 450. The sound is almost inaudible. Why amplification occurs?

"The speed of sound propagation" - In solids - even faster. What are the units of loudness and sound volume level. What determines the sound volume? How does the systematic action of loud sounds affect human health? What determines the pitch of a sound? What is the fundamental tone and overtones of sound? The speed of sound in air is » 330 m/s.

In total there are 34 presentations in the topic

Speaking about the structure of the auditory apparatus, we are moving gradually to the principle of analysis by the brain of the signal received from the cochlea. What is it? And how does the brain decipher it? How does he determine the pitch of a sound? Today we will just talk about the latter, since it automatically reveals the answers to the first two questions.

It should be noted that the brain detects only the periodic sinusoidal components of the sound. Human pitch perception also depends on loudness and duration. In the last article, we talked about the basilar membrane and its structure. As you know, it has a heterogeneity in the rigidity of the structure. This allows it to mechanically break down sound into components that have special place placement on its surface. From where the hair cells later send a signal to the brain. Due to this structural feature of the membrane, the "sound" wave running over its surface has different maxima: low frequencies - near the top of the membrane, high - at the oval window. The brain automatically tries to determine the height from this " topographic map”, finding the localization of the fundamental frequency on it. This method can be associated with a multiband filter. This is where the "critical bands" theory we discussed earlier comes from:

But this is not the only approach! The second way is to determine the pitch by harmonics: if you find the minimum frequency difference between them, then it is always equal to the fundamental frequency - [( n +1) f 0 - (nf 0)]= f 0, where n are harmonic numbers. And also, together with it, the third method is used: finding the common factor from dividing all harmonics into successive numbers and, pushing from it, the pitch is determined. Experiments fully confirmed the validity of these methods: the auditory system, finding the maxima of the harmonics, performs computational operations on them, and even if you cut out the fundamental tone or arrange the harmonics in an odd sequence, in which method 1 and 2 do not help, then a person determines the pitch of the sound by method 3.

But as it turned out - this is not all the possibilities of the brain! Cunning experiments were carried out that surprised scientists. The point is that the three methods work only with the first 6-7 harmonics. When one harmonic of the sound spectrum falls into each “critical band”, the brain calmly “determines” them. But if some harmonics are so close to each other that several of them fall into one area of ​​​​the auditory filter, then the brain recognizes them worse or does not determine them at all: this applies to sounds with harmonics above the seventh. This is where the fourth method comes in - the “time” method: the brain begins to analyze the time of receipt of signals from the organ of Corti with the phase of oscillation of the entire basilar membrane. This effect is called "phase locking". The thing is that when the membrane vibrates, when it moves towards the hair cells, they come into contact with it, forming a nerve impulse.
When driving back, no electrical potential does not appear. A relationship appears - the time between pulses in any individual fiber will be equal to the integer number 1, 2, 3, and so on, multiplied by the period in the main sound wave f = nT . How does this help in working in conjunction with critical bands? Very simple: we know that when two harmonics are so close that they fall into the same "frequency region", then between them there is a "beating" effect (which musicians hear when tuning the instrument) - it's just one oscillation with an average frequency equal to the difference frequencies. In this case, they will have a period T =1/f 0. Thus, all periods above the sixth harmonic are the same or have a bit in an integer, that is, the value n/f 0. Next, the brain simply calculates the pitch frequency.