Is it always convenient to use Newton’s laws. Jet engine. Octopus. Baron Munchausen. What movement is called reactive. Jet propulsion. Story. Modern technologies for the production of rocket launchers. Body movement. Cyrano de Bergerac. Jet movement in nature. Rocket. Konstantin Eduardovich Tsiolkovsky (1857-1935).
“Principle of a nuclear reactor” - Use of nuclear reactors. Types of reactors. What is the critical mass of uranium 295? What mass of uranium is critical. Nuclear reactor. The main elements of a nuclear reactor. What energy conversions take place in a nuclear reactor. Energy conversion. Reiteration. Fast neutron reactors. The reactor is controlled by rods. What particles are involved in the fission of uranium nuclei.
“Ohm's Law for a Circuit” - An experiment proving that the resistance of a conductor decreases. Ohm's Law. Mentally, in the vicinity of the point, we select a small cylindrical volume. Experimental verification of the relationship between current and voltage. The resistance of the conductor decreases with cooling. The concentration of free electrons in the metal. Analysis of the results of the experiment. Table of measurements of voltage and current for an incandescent lamp.
“Technologies of the future” - Forecast for the development of the nanotechnology products market for 2015. What are they giving now. In the Tomsk Academgorodok, a technology-innovative zone is being built. Creation of micro - nano - electromechanical systems. Companies that do not want to build separate buildings for themselves. "There is still a lot of space down there." XXI century is the century of nanoscience and nanotechnology. At first. Nanotechnology tomorrow. A new direction in technology. Nanotechnology today.
"" The nature of light "physics" - Photon. Properties of electromagnetic waves. The electromagnetic nature of light. Christian Huygens. Thus, light has wave-particle properties. Einstein (1879–1965). Isaac Newton. 1642-1727. Views on the nature of light in the XVII-XIX centuries. The transition of energy from light to matter or from matter to light obeys the relation E \u003d h ?. Municipal budgetary educational institution "Secondary school No. 46" of the city of Ryazan.
“Nuclear energy safety” - NPPs have more opportunities in energy production. Nuclear power. From the history of nuclear energy. Security. Nuclear power plants. The decay of uranium nuclei. Scheme of operation of a boiling nuclear reactor. The benefits and harms of nuclear energy. Nuclear power plants on a map of Russia. Thermonuclear fusion. Scheme of a boiling nuclear reactor. The harm of nuclear energy. Nuclear-powered icebreakers. Nuclear reactor.
Sound, in the broad sense, the oscillatory motion of particles of an elastic medium propagating in the form of waves in a gaseous, liquid, or solid medium in the narrow sense is a phenomenon subjectively perceived by a special sensory organ of humans and animals. A person hears Z. with a frequency of 16 hzup to 20,000 hzThe physical concept of Z. covers both audible and inaudible sounds. H. with a frequency below 16 hzcalled infrasound, above 20,000 Hz - ultrasound; the highest-frequency elastic waves in the range from 10 9 to 10 12 -10 13 hzattributed to hypersound. The range of infrasound frequencies from below is practically unlimited - in nature there are infrasound vibrations with a frequency of tenths and hundredths hzThe frequency range of hypersonic waves from above is limited by physical factors characterizing the atomic and molecular structure of the medium: the elastic wavelength should be significantly longer than the mean free path of molecules in gases and greater than the interatomic distance in liquids and solidsoh. Therefore, hypersound with a frequency of 10 9 cannot propagate in air. hzand higher, and in solids - with a frequency of more than 1012-10 13 Hz
The main characteristics of sound.An important characteristic of the waveform is its spectrum, obtained as a result of the decomposition of the waveform into simple harmonic oscillations (the so-called frequency sound analysis). The spectrum is continuous when the energy of sound vibrations is continuously distributed in a more or less wide range of frequencies, and linear when there is a combination of discrete (discontinuous) frequency components. Z. with a continuous spectrum is perceived as noise, for example, the rustling of trees under the wind, the sounds of working mechanisms. Musical waveforms have a linear spectrum with multiple frequencies (the fundamental frequency determines the pitch of the sound that is perceived by ear, and the set of harmonic components determines the sound timbre. The spectrum of waveforms contains formants - stable groups of frequency components that correspond to certain phonetic elements. The energy characteristic of sound of oscillations is the intensity of sound - the energy carried by a sound wave through a unit of surface perpendicular to the direction of wave propagation, per unit time. The intensity of sound depends on the amplitude of sound pressure, as well as on the properties of the medium itself and on the waveform.The subjective characteristic of sound, related to its intensity, is the volume of sound, depending on the frequency.The human ear has the greatest sensitivity in the frequency range 1-5 khzIn this area, the threshold of audibility, i.e., the intensity of the weakest audible sounds, is 10-12 in order of magnitude vm / m 2 and the corresponding sound pressure is 10 -5 n / m 2 . The upper intensity boundary of the region perceived by the human ear Z. is characterized by a threshold of pain sensation, weakly depending on the frequency in the audible range and equal to about 1 vm / m 2 . In ultrasonic technology, significantly higher intensities are achieved (up to 10 4 sqm / m 2 ).
Sound sources- any phenomena that cause a local change in pressure or mechanical stress. Z. sources in the form of oscillating solids are widespread (for example, speaker diffusers and telephone membranes, strings and decks of musical instruments; in the ultrasonic frequency range, plates and rods made of piezoelectric materials or magnetostrictive materials) . Z.'s sources can also be fluctuations of limited volumes of the medium itself (for example, in organ pipes, wind musical instruments, whistles, etc.). A complex oscillatory system is the vocal apparatus of humans and animals. Excitation of oscillations of Z. sources can be made by a blow or a pinch (bells, strings); they can support the mode of self-oscillations due to, for example, air flow (wind instruments). An extensive class of Z sources is electro-acoustic transducers in which mechanical vibrations are created by converting electric current oscillations of the same frequency. In nature, earth is excited when air flows around solids due to the formation and separation of vortices, for example, when wind blows wires, pipes, and crests of sea waves. Z. low and infra-low frequencies occurs during explosions, collapses. The sources of acoustic noise are diverse, which include machines and mechanisms used in engineering, gas and water jets. The study of sources of industrial, traffic noise and noise of aerodynamic origin is given great attention due to their harmful effects on the human body and technical equipment.
Sound receivers are used to perceive sound energy and transform it into other forms. Z.'s receivers include, in particular, the hearing aid of humans and animals. In the technique for receiving Z., electroacoustic transducers are mainly used: microphones in air, hydrophones in water, and geophones in the earth's crust. Along with such transducers, reproducing the time dependence of the sound signal, there are receivers measuring the time-averaged characteristics of the sound wave, for example, Rayleigh disk, radiometer.
The propagation of sound waves is characterized primarily by the speed of sound. Longitudinal waves propagate in gaseous and liquid media (the direction of the oscillatory motion of the particles coincides with the direction of wave propagation), the speed of which is determined by the compressibility of the medium and its density. The speed of air in dry air at a temperature of 0? C is 330 m / s, in fresh water at 17? C - 1430 m / sIn solids, in addition to longitudinal waves, transverse waves can propagate, with a direction of oscillation perpendicular to the wave propagation, as well as surface waves (Rayleigh waves) . For most metals, the velocity of longitudinal waves is in the range of 4000 m / sup to 7000 m / sand transverse - from 2000 m / sup to 3500 m / s
When waves of large amplitude propagate (see Nonlinear Acoustics), the compression phase propagates at a faster rate than the rarefaction phase, due to which the sinusoidal wave shape is gradually distorted and the sound wave turns into a shock wave. In some cases, dispersion of sound is observed, i.e., the dependence of the propagation velocity on frequency. Z. dispersion leads to a change in the shape of complex acoustic signals, including a number of harmonic components, in particular, to distortion of sound pulses. When sound waves propagate, interference and diffraction phenomena common to all types of waves take place. In the case when the size of obstacles and inhomogeneities in the medium is large compared to the wavelength, the propagation of sound obeys the usual laws of reflection and refraction of waves and can be considered from the perspective of geometric acoustics.
When a sound wave propagates in a given direction, its gradual attenuation occurs, i.e., a decrease in intensity and amplitude. Knowledge of the laws of attenuation is practically important for determining the ultimate propagation range of an audio signal. Attenuation is caused by a number of factors that manifest themselves to one degree or another depending on the characteristics of the sound itself (and first of all, its frequency) and on the properties of the medium. All these factors can be divided into two large groups. The first includes factors related to the laws of wave propagation in the medium. So, when propagating in an unlimited medium, the earth from a source of finite size, its intensity decreases inversely with the square of the distance. The inhomogeneity of the properties of the medium causes scattering of the sound wave in different directions, leading to its weakening in the initial direction, for example, scattering of stars by bubbles in water, on an excited surface of the sea, in a turbulent atmosphere (see Turbulence), scattering of high-frequency ultrasound in polycrystalline metals, by dislocations in crystals. The distribution of earth in the atmosphere and in the sea is affected by the distribution of temperature and pressure, wind strength and speed. These factors cause the bending of sound rays, i.e., refraction of the earth, which explains, in particular, the fact that the earth is heard farther in the wind than against the wind. The distribution of the Earth's velocity with depth in the ocean explains the presence of so-called. an underwater sound channel in which an extra long propagation of the earth is observed, for example, an earth’s explosion propagates in such a channel to a distance of more than 5000 km
The second group of factors determining the attenuation of earth is associated with physical processes in matter — the irreversible transition of sound energy into other forms (mainly into heat), that is, with sound absorption due to the viscosity and thermal conductivity of the medium (“classical absorption”) , as well as the transition of sound energy into the energy of intramolecular processes (molecular or relaxation absorption). Absorption of Z. increases markedly with frequency. Therefore, high-frequency ultrasound and hypersound, as a rule, propagate only over very short distances, often only a few cm.In the atmosphere, in the aquatic environment and in the earth's crust, infra sound wavescharacterized by low absorption and weakly scattered. At high ultrasonic and hypersonic frequencies in the solid, additional absorption occurs due to the interaction of the wave with the thermal vibrations of the crystal lattice, with electrons and with light waves. Under certain conditions, this interaction can also cause “negative absorption,” that is, amplification of the sound wave.
The value of sound waves, and consequently, their study, which deals with acoustics, is extremely large. For a long time Z. serves as a means of communication and signaling. The study of all its characteristics allows us to develop more advanced information transmission systems, increase the range of alarm systems, and create more advanced musical instruments. Sound waves are almost the only type of signals propagating in the aquatic environment, where they serve for purposes of underwater communication, navigation, and location (see Hydroacoustics). Low-frequency sound is a tool for studying the earth's crust. The practical application of ultrasound has created an entire branch of modern technology - ultrasonic technology. Ultrasound is used both for control and measuring purposes (in particular, in flaw detection), and for active action on a substance (ultrasonic cleaning, machining, welding, etc.). High-frequency sound waves and especially hypersound serve as the most important research tool in solid state physics.
Sound intensity level
Using Definitions whiteand decibelwe can formulate a definition accepted in acoustics the basic concept - "The level of intensity (strength) of sound -L " atdb and write down its conditional formula (28) :( 28)
In mathematical form, formula (28), taking into account proportionality (21), will take the form of formula (29): (29) Sound intensity (strength) level -L (db) is an abstract concept that is used in practical calculations instead of a specific physical concept - the intensity (power) of sound. At the same time, it can be used to explain many contradictions between objective and subjective assessments of sound. Taking into account identity (11) in world practice, the following definition of this concept is accepted:
Level the intensity (strength) of sound, expressed in decibels, is the twenty-fold logarithm of the ratio of the absolute value of the sound pressure p to the basic value of the sound pressure p0= 2 10-5 N / m2 standard tone frequency f = 1000 Hz on the verge of hearing EIZ \u003d 10-12W / m2 established by international agreement. It is very important to understand that the level of intensity (power) of sound is not a physical, but a purely mathematical concept.
Understanding that the level of intensity (power) of sound is not a physical, but a purely mathematical concept very important for understanding many of the "secrets of acoustics."
Any phenomenon in our World has any quantitative and qualitative indicators that can be measured, and therefore changed, having received predictable, in most cases, consequences. And the sound was no exception to the rule!
For him, the same parameters and indicators apply as for the surrounding world. The study of these parameters and indicators is the science of “Acoustics”.
Sound vibrations can be graphically represented in the form of a graph of body motion that generates sound. If we are talking about dynamics that reproduces sound, then the graph will display the movement of the diffuser. If we are talking about a string, then a graph of the oscillation of the string. If there is any wind instrument, then a graph of the oscillation of air inside the instrument tube, etc.
To describe a phenomenon such as sound, you must first understand - and what we actually hear.
- Well, firstly - the volume, we distinguish between loud and quiet sounds.
- Secondly, the pitch, we distinguish the sounds that make up the melody.
- Thirdly, we perceive a change in the volume of individual sounds.
- Fourth, we distinguish the sound of one instrument from another, for example, a piano from a guitar, we hear their unique timbre.
To understand how all this works, you need to imagine the whole picture.
Consider the dynamics of the diffuser.
It is worth mentioning that he cannot reproduce two sounds at the same time, he moves linearly, within certain limits.
The movement of the diffuser has an amplitude:
Roughly speaking, this is the distance to which he can deviate from a state of rest.
When it plays an audio signal, it moves within these limits:
When moving, it creates tension in the air, then squeezing it, then discharging it in turn. This effect of the diffuser on the air creates “sound pressure” in the air. If the strength of the signal entering the speaker increases, then the amplitude of the diffuser increases:
Following the amplitude, the speed of the diffuser also increases, since it needs to travel a greater distance in the same time - the wave is one, the amplitudes are different. Since the speed has increased, it turns out that the diffuser compresses and discharges air faster, and if air compresses faster, then the pressure that occurs in the air becomes greater. Accordingly, reaching our ears, the air sways the eardrum more strongly, as a result of this, the stimulation of the nerves becomes larger and we perceive that the sound has become louder. Such are the things.
From the same example, you can see that, despite the fact that the wave amplitude has increased, the time segments for both waves are the same, this is due to the "oscillation frequency", the next parameter that we can hear. In fact, the oscillation frequency is the pitch, it is this parameter that is responsible for how we hear the sound - high or low. The higher the frequency, the more the sound we hear is higher, the lower the frequency, the lower the sound.
Frequency is measured in Hertz (Hz).
1 Hertz is one wobble per second.
The hearing threshold of human hearing is from 20 to 20,000 Hz.
Each note corresponds to a certain amount of vibrations. Thus, a diffuser in dynamics that plays any kind of music pumps the air not only with a certain amplitude, affecting the volume of the music being heard, but also with a certain frequency. That is, he makes either more or less hesitation, depending on the melody. In order to at least a little imagine the speed of the speaker, we can say that the note “A” of the first octave corresponds to a frequency of 440 Hz. That is, if we hear “A” note from the speaker for one second, then in this very second, the speaker will make 440 vibrations.
The frequency of sound also affects the volume, but this already applies more to the “psychoacoustics” section, as it affects the issue of human perception of sound. Our hearing aid is designed in such a way that we perceive high frequencies louder than low ones when it comes to “sound pressure”. That is, if we take two sounds - low and high and adjust their volume so that they create the same sound pressure, then high will seem much louder.
The next thing that we can distinguish in sound is its ADSR envelope. The concept of ADSR refers more to single sounds and most often to the sounds of synthesizers in digital sound synthesis. ADSR is an acronym for English words Attack (Attack), Decay (Decay), Sustaine (Sounding) and Release (Attenuation). A little later, we will separately discuss this in more detail, but now it’s worth briefly explaining the essence. Imagine that you took a guitar and pulled a string on it. First, you will hear that the sound appeared very quickly, literally right away (Attack), then the volume will decrease a little (Decay), hold on a bit (Sound) and die down (Decay).
In most cases, under ADSR they mean precisely the stages of sound formation and their adjustment. In digital synthesis, these parameters are set in milliseconds; when playing an instrument, the performer controls them.
Another audible sound quality is the timbre of the instrument and our ability to distinguish between these timbres.
The topic is complex and will be most fully disclosed during our review of various tools. Almost everything that is in the instrument affects the timbre, to a greater or lesser extent. The first and main thing is of course a way of sound production. That is the principle of the tool. On the violin, the strings are bowed, the strings are pulled on the guitar, the hammers are struck on the strings, the winds are blowed, as a result, the sound of an instrument is born. At the same time, each instrument has its own unique sound. So, two guitars will not sound the same, something will differ in their sound, although it will still be the sound of a guitar.
This is a very interesting topic, which we will discuss in more detail.
Of the most obvious sound phenomena, we examined everything, but not the obvious ones, but about them another time.
SOUND WAVES
The world of sounds is so diverse
Rich, handsome, diverse
But the question that all torments us
What do our ears always delight?
It's time to think seriously.
The reason for the sound? - vibration (vibrations) of bodies, although these vibrations are often invisible to our eyes.
Sources of sound are physical bodies that oscillate, 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 crust, gaseous, for example, a stream of air in wind musical instruments or in a whistle, or liquid, for example, waves on water.
Around an oscillating body, environmental vibrations occur, which propagate in space.
Sound is mechanical elastic wavespropagating in gases, liquids, solids.
Waves that cause a sensation of sound, with frequencies from 16 Hz to 20,000 Hzare called
sound waves (mostly longitudinal).
DO IT YOURSELF!
If you bring a bead on a string to a glass or glass jar and strike, for example,
pencil on the wall of the glass, then we will see the vibrations of the bead and hear its ringing.
TO HEAR THE SOUND
necessary:
1. sound source;
2. the elastic medium between him and the ear;
3. a certain range of frequencies of oscillations of the sound source - between 16 Hz and 20 kHz,
sufficient for the perception of the ear power of sound waves.
SOUND CHARACTERISTICS
Volume.
.
The volume depends on the amplitude of the oscillations in the sound wave.
The unit of sound volume is 1 Bel (in honor of Alexander Graham Bell, the inventor of the phone). The sound volume is 1 B if its power is 10 times the hearing threshold.
In practice, the volume is measured in decibels (dB).
1 dB \u003d 0.1B. 10 dB - whisper; 20-30 dB - noise norm in residential premises;
50 dB - medium volume conversation;
70 dB - typewriter noise;
80 dB - noise of a running truck engine;
120 dB - noise of a working tractor at a distance of 1 m
130 dB is the threshold of pain.
Sound with a volume above 180 dB can even cause the eardrum to rupture.
Pitch
It is determined by the oscillation frequency of the sound source.
The sounds of a human voice are divided by height several ranges:
bass - 80-350 Hz,
baritone - 110–149 Hz,
tenor - 130-520 Hz,
treble - 260-1000 Hz,
soprano - 260-1050 Hz,
coloratura soprano - up to 1400 Hz.
The frequency spectrum of the sounds of musical instruments.
According to legend, Pythagoras arranged all musical sounds in a row, breaking this row into parts - octaves, and an octave - into 12 parts (7 basic tones and 5 half tones). In total, there are 10 octaves, usually 7–8 octaves are used in performing musical works. Sounds with a frequency of more than 3000 Hz are not used as musical tones; they are too sharp and piercing.
ANIMAL PERFECTED FREQUENCY RANGE OF ANIMALS
BOOKSHELF
INTERESTING PHENOMENA!
ABOUT SOUNDS IN LITERATURE ...
(Noise is an erratic mixture of musical sounds.)
DO NOT MAKE NOISE!
Are we noisy?
Well, Andryusha pounded barely
An iron pipe hammer,
I played softly on my lip
Eight-fifths of the size keeping,
Tanya slammed the barn door
Sasha drove a stone along the glass,
Tolya hit the pan in the corner.
With a brick! But quietly and rarely.
“Don’t make a noise!” Said the neighbor,
And no one thought to make noise .....
Al Kushner.
Why does the drum sound?
One day, the leader, Hawkeye, and the shaman Snake tongue met.
"Why does the drum sound?" the shaman asked.
The leader quickly answered: "Because he was hit."
The shaman responded very quickly: "The sound after the strike lasts noticeably longer than the strike itself."
Then the leader and the shaman demanded the biggest drum.
First, the leader struck, and the shaman touched the drum skin, then - on the contrary.
In the end, they noticed that the skin was trembling, and when it was trembling, a sound was heard.
Here the leader, who was as strong in conjecture as the shaman in riddles, expressed the Great Guess:
ALL SOUND - SHAKES !!!
At the same time, the leader screamed with delight so that the shaman’s ears rang.
Not remembering himself in pain, the shaman grabbed the leader by the throat. The throat was trembling!
The shaman released the leader and took the Watchtower Jaguar, who purred at the entrance, by the scruff of the neck.
The scruff shook!
Then the leader stopped yelling and issued the second Great Guess:
ALL SHAKING - SOUND !!!
Instead of an insidious question, the shaman brought a convulsively clenched fist to the leader’s nose.
The fist (and the whole hand) trembled - but did not sound. The second great conjecture had to be corrected:
NOT ALL SHAKING SOUND!
Meanwhile, the shaman had another insidious question:
"How to tremble to sound?"
The leader recalled a recent battle: if a long arrow pierces a tree trunk, it trembles soundlessly, if it is short, it sounds. The shaman pulled out the longest arrow, pressed the feathered end to a flat stone, and the leader bent the sharp end down - and immediately released it.
Then he made the free end shorter - and again he let go.
The leader’s response, not without reason was called Hawkeye, was this:
"An arrow begins to sound when its trembling ceases to be visible to the eye - it is so frequent."
The shaman asked the leader to switch places: now the leader held the feathered end of the arrow, and
the shaman rejected and released the tip. The shaman Snake tongue was weaker than the leader, and each time he rejected the tip not so much. How did the sound change?
HORN - AUDIO AMPLIFIER
Often in competitions, when the coach or referee needs to inform the athlete over a long distance, a shout is used. It can be a rather complicated device - a megaphone, but you can get by with a simple newspaper folded into a bag. You can make horns from large sheets of whatman paper. If in a classroom two such horns are placed at opposite walls, then you can talk with their help in a whisper.
WE LISTEN TO MUSIC!
To demonstrate how shout amplifies soundmake from thick paper
a small shout, and stick it into its thin end perpendicular to the surface of the paper
sewing needle. Insert pencil in the hole records of some kind of music.
Press the sharp end of the pencil with the plate onto the surface of the table and begin to rotate the plate by quickly turning the pencil. With the other hand, place the tip of the speaker needle on the sound groove of the plate. Listen! There should be a sound!
TRY IT!
And if you take 2 thin rubber tubes insert into the narrow end of the horn, wrap with insulating tape, and insert the free ends of these tubes into both ears, then with such a simple device distant and weak sounds will be heard much better.
For example, remember why a doctor needs a stethoscope?
With what help did E.K. Tsiolkovsky try to compensate for deafness?
Why does a person put a palm to his ear, trying to make out hard-to-hear sounds?
THIS IS YES!
Found that when it becomes difficult for a plant to extract water from dry soil,
the plant stem begins emit ultrasonic noise.Attached to the stems
special microphones, you can catch these noises and include irrigation systems
only when the plants themselves require it
The sound of snoring can reach 69 decibels, which is comparable to the sound jackhammer.
___
The loudest noiseobtained in the laboratory, was equal to 210 dB. He was received
due to the reflection of sound by a reinforced concrete test bench designed for rocket tests at the US Space Flight Center, in 1965, a sound wave of such strength could drill holesin solid materials. Noise was heard within 161 km.
The highest received note has a frequency of 60 gigahertz. It was generated by a laser beam aimed at a sapphire crystal, in the USA, in 1964.
Quietest place - this is Dead room at the Bell Telephone Systems Laboratory in the USA, it is the most sound-absorbing room in the world in which 99.98% of the reflected sound disappears.
DO IT YOURSELF!
Home-made phone from a thread and matchboxes.
Take 2 matchboxes(or any other boxes of suitable sizes: from powder, tooth powder, paper clips) and a thread several meters long (you can use the entire length of the school class) .Put a box with a needle and a thread on the thread and tie a knot on the thread so that it does not pop out. Thus, both boxes will be connected using a thread. Two people participate in a telephone conversation: one speaks into the boxes, like into a microphone, the other listens, holding the boxes to his ear. During the conversation, the thread should be tight and should not touch any objects, including the fingers that hold the boxes. If you touch finger to the thread, the conversation will immediately end. Why?
Musical instruments.
If you take several empty identical bottles, line them in a row and fill with water (the first with a small amount of water, the subsequent ones fill up progressively, and the last fill up to the top), you get a musical percussion instrument. By hitting the bottles with a spoon, we will make the water oscillate. The sounds from the bottles will vary in pitch.
We take a cardboard tube, insert a stopper with an stuck knitting needle into it like a piston, and moving the piston, blow it to the edge of the tube. The flute sounds!
We take a box with not falling edges, we put on rubber bands (the tighter they wrap around the box, the better), and the harp is ready! Going through the gum like strings, listen to the melody!
Another “musical” toy.
If you take a piece of corrugated plastic tube and unwind it over your head, you will hear a musical sound. More than rotational speed, the higher the pitch. Experiment! I wonder what caused the appearance of sound in this case?
DO YOU KNOW?
Airplane flying with supersonic speedovertakes the sounds it creates. These sound waves merge into one shock wave. Reaching the surface of the earth, the shock wave knocks glass, destroys buildings, stuns.
The sound made by a blue whale is louder than the sound of a shot nearby heavy guns or louder than the sound of a rocket launching.
When meteorites pass through the Earth’s atmosphere, a shock wave is excited, the speed of which is one hundred times higher than the sound wave, and a sharp sound similar to the sound of tearing matter.
With a skilled whip strike, a powerful wave is generated along it, the propagation velocity of which at the tip of the whip can reach huge values!As a result, a powerful shock sound wave arises, comparable to the sound of a shot.
MYSTERIOUS WHISPERING GALLERY
Lord Rayleigh was the first to explain whisper gallery riddlelocated under the dome of London's St. Paul's Cathedral. A whisper is heard very well in this large gallery. If, for example, your friend whispered something, turning to the wall, then you will hear it, no matter where in the gallery you are standing.
Oddly enough, you hear him the better, the more “directly into the wall” he speaks and the closer to him. Is this task simply reduced to reflection and focus sound? To explore this, Rayleigh fabricated a large gallery model. At one point of it he placed a decoy - a whistle, which hunters lure birds to, at another - a sensitive flame that was sensitive to sound. When the sound waves from the whistle reached the flame, it began to flicker and thus served as an indicator of sound. You would probably draw the path of sound as shown by the arrow in the figure. But, in order not to take it on faith, imagine that somewhere between the flame and the whistle near the wall of the gallery there is a narrow screen. If your assumption regarding the course of sound waves is correct, then with the sound of a whistle, the flame should still flicker, since the screen would seem to be on the side! However, in reality, when Rayleigh installed this screen, the flame stopped flickering. Somehow, the screen blocked the path of sound. But how? After all, this is just a narrow screen and it seems to be located away from the sound path. The result gave Rayleigh a clue to the secret of the whispering gallery.
Whispers Gallery (sectional view)
Whispering gallery model made by Rayleigh. The sound of a whistle makes the flame flicker.
If a thin screen is installed at the wall of the gallery model, the flame does not respond to the sounds of whistles. Why? Reflecting continuously from the walls of the dome, sound waves propagate in a narrow belt along the wall. If the observer is inside this belt, he hears a whisper. Outside this belt, further from the wall, a whisper is not heard. A whisper is heard better than ordinary speech, as it is richer in high-frequency sounds, and the “audibility belt” is wider for high frequencies. In this case, sound propagates as if in a cylindrical waveguide, and its intensity decreases with distance much more slowly than when propagating in open space.
Noisy water pipes.
Why water pipes sometimes start to growl and moanwhen do we open or close the tap? Why is this not happening continuously? Where exactly does the sound appear: in the water tap, in the part of the pipe adjacent directly to the tap, or in some bend somewhere further? Why does noise begin only at certain levels of water flow? Finally, why can noise be eliminated by attaching to the water pipe a vertical tube that is closed at the other end and containing air? With an increase in the flow velocity in the places of narrowing in the pipes, turbulence can occur, which leads to cavitation (the formation and rupture of bubbles). Fluctuations of bubbles are amplified by pipes, as well as walls, floors, and ceilings to which the pipes are attached !. Sometimes noise can also be caused by periodic blows of a turbulent flow about obstacles (for example, narrowing) in a pipe.
Can fish talk?
Fish speak human language, only in fairy tales, but they are not deaf at all and can make sounds. They make various sounds with the help of teeth, an air bubble, a tail. Sounds serve to communicate and scare away enemies. Fishermen know that a gudgeon can squeak, and bream make gurgling sounds.
But fish perceive sound. So the predators rush to the place where there was a surge of other, small fish.
The loudest noiseobtained in laboratory conditions, was equal to 210 dB, or 400 thousand ac. Watts (acoustic watts), NASA reported. It was obtained due to the reflection of sound by a reinforced concrete test bench measuring 14.63 m and a foundation 18.3 m deep, designed for testing the Saturn V rocket at the Space Flight Center named after Marshall, Huntsville, Alabama, USA, in October 1965. A sound wave of such strength could have drilled holes in solid materials. Noise was heard within 161 km.
Energy that usually carry sound wavesvery small. If a glass of water completely absorbed all the sound energy incident on it, corresponding to a loud enough loud speech, and was completely insulated from the environment, then it would take about 30 thousand years to heat water from room temperature to a boil!
AMAZING NEARBY!
Try to complete this experience and surprise your relatives!
Your instrument will be a glass (not crystal) thin-walled glass on the leg, with a capacity of half to a glass of liquid.
The glass of the glass should be clean, smooth, not painted with anything. Having picked up the instrument, proceed to test its musical qualities. Before starting the experiment, wash your hands well with soap. Then, slightly wetting your fingers with clean water right hand, put the glass on the table, and firmly hold its leg with your left hand. With the middle or index finger of your right hand, start round drivearound the edge of the glass .. in a few seconds you should hear melodious sound. The sound will not stop while you are driving along the edge of the glass. If this succeeds, pour clean water into the glass, not reaching the edge a little, and continue to drive with your finger. You should hear a sound well below that which was without water. Continuing your circular motions with your finger, look at the surface of the water. Small waves formed on it. They came from the hesitant, sounding walls glasses. Now begin to gradually remove the water in small portions. The sound will gradually increase and the highest will be at the empty glass.
If you surprise me with this experience, then a "5" will appear in the magazine!
SOUND BLOCK
Make a hole about 1 cm in diameter in the bottom of the plastic bucket of mayonnaise
close the bucket with a lid, put a burning candle in front of the hole. Hit the lid with your hand - the candle will go out. Sound extinguishes a candle.
Homemade SIREN
Take a wooden circle, do it holes along circles of different radiiat the right intervals. Start rotating it vertically. Direct a stream of air from a vacuum cleaner hose into openings of each circle. Will the sounds be different? How to make the sound louder, higher or lower? Can you explain how the siren works?
SOUNDS DESERT
Very often in the literature mention of mysterious sounds that can be heard in the desert. Today it is known that these sounds result from the movement of sand layers, but there is no complete explanation of these phenomena.
There are two types of sounding sand - “Buzzing” and “whistling”which differ in the frequency and duration of sound and occur under different conditions.
Whistling sounds - easy whistling of sand underfoot can be heard on the sea coasts, on the banks of rivers and lakes around the world. These are acoustic vibrations of grains of sand with a frequency of 500 to 2500 Hz.
Humming sounds - they arise deep in the desert near individual large dunes. This is a loud low frequency sound of 50-300 Hz, usually lasting from a few seconds to 15 minutes. They are carried at distances of up to 10 kilometers, and are often accompanied by soil vibrations.
Sands consisting of quartz whistle and buzz.
And here is the sound of the sands of Hawaii resembles a dog barking. Hawaiian sands are the only sounding sands that are not made of quartz.