# Why does the circular saw sound pitch decrease?

## § 35. The pitch and timbre of the sound

In the experiment in Fig. 70 we have a ruler clamped in a vise, and it makes a sound when it vibrates. Moving the ruler in the vise, so that its oscillating piece is reduced, we notice that when the shorter part of the ruler oscillates, the sound it produces becomes higher, and the frequency of oscillation increases. From this experience we can conclude that as the frequency of oscillation increases, the height of the sound increases.

What was the purpose of the experiment shown in Figure 75?? Describe how this experiment was conducted and what conclusion was drawn.

In the experiment in Fig. 75 When a cardboard plate in contact with a rotating toothed disc, a toothed disc audibly vibrates. As the speed of the toothed disc increases, the frequency of vibration and the corresponding increase in pitch.

How can you verify by experience that the higher tone produced by the one with the larger natural frequency of the two tuning forks?? (Frequencies are not indicated on the tuning forks).

The chamberton with the higher tone on the smoked plate will leave a more frequent trace, t.е. oscillates at a higher frequency (see “Tone of sound” on page 13). Figure. 76)

The pitch of a sound depends on the frequency.

What is called a pure tone?

A pure tone is the sound of source that vibrates at the same frequency.

What are the fundamental tone and overtones of a sound?

Base tone. The frequency component of a complex sound with the lowest (smallest) frequency of vibration. Overtones. The total of the frequency components of a sound without its fundamental tone. The overtone frequencies are multiples of the fundamental frequency.

What is determined by the pitch of a sound?

The pitch of a sound is determined by the pitch of the fundamental tone.

What is the timbre of a sound and how is it defined?

Sound timbre. an overtone coloration of the sound; a specific characteristic of the musical sound. The timbre of a sound is determined by the totality of its overtones.

Which insect flaps its wings more often in flight? bumblebee, mosquito, or fly? Why do you think so??

The higher the frequency, the higher the sound. Consequently, a mosquito, flaps its wings more often.

The teeth of a rotating circular saw create a sound wave in the air. How will the pitch of the sound produced by the saw change when it is idling if you start sawing a thick board of dense wood on it? Why?

The height of the sound will decrease, t.к. The rotational frequency of the circular saw will decrease.

It is known that the tighter the string on the guitar, the higher the sound it makes. How will the pitch of guitar strings change if the ambient temperature rises significantly? Explain the answer.

As the temperature rises, the guitar string stretches, hence the period of oscillation increases, and hence the frequency and pitch of the sound decreases.

## The Great Encyclopedia of Oil and Gas

tone. the volume of the signal and the strength of the current consumed depend on the size of the air gap between the armature and the core, which is ensured by the selection of shims between the body and the diaphragm, and also on the size of the gap between the contacts of the chopper.  [1]

How does the pitch of a circular saw change. when it plunges into a log to be sawn.  [2]

When the operator gets tired, the pitch of the sound seems to change, as well as when the sound intensity changes.  [3]

Acoustic method is based on the difference in sound tones when tapping serviceable parts and parts with cracks, as well as parts with normal and loose fit. The acoustic method is beginning to be widely used for technical diagnostics of operating mechanisms without disassembly.  [4]

The vibration frequency of the diaphragm, and hence the tone of the sound, is determined by the mass of the weights 7 mounted on the armature. The low tone signal has two weights 7 rectangular in shape, and the high tone signal. only one load of 10 smaller.  [5]

For example, the pitch of a sound increases as the sound source gets closer. This is easily noticed by listening to the sound of a siren of an approaching train. As the sound source moves away, the pitch of the sound decreases.  [6]

Doubling the frequency at any initial frequency increases the tone of the sound always by the same amount, called an octave.  [7]

The cochlea has a transparent base membrane that detects the pitch of sound. One end of the main membrane near the eardrum resonates at a frequency of 20 kHz, and the other end of the main membrane resonates at a frequency of 20 Hz. The cochlea has a nerve in the cochlea which, because of its sensory endings in the main membrane, converts mechanical vibrations into bioelectrical signals and sends them to the corresponding center in the brain, where they are perceived as sound sensations. Information about the relative phases of the same sound signal is not perceived by the human ear. Apparently, during evolutionary development, the brain did not record signals carrying information about the phase of the sound signal. With a hearing aid, a person receives up to 10 % of information.  [8]

The oscillograms show ( Fig. 213) that the sense of pitch of the sound depends on the oscillation frequency.  [9]

A further change in the reference frequency / 0 should be such that the tone of the sound in the telephone decreases. At a difference frequency of about 15. 20 Hz the sound in the telephone disappears.  [10]

Sound signals require skillful adjustment, since both the tone of the sound produced and the magnitude of the current depend on it.  [12]

With a larger deflection of plate 6 and a smaller gap between the armature and the core, the oscillation frequency of the diaphragm increases and the pitch of the sound increases.  [14]

Note that as the voltage of the power supply decreases, the oscillation frequency of the oscillator and hence the tone of the sound EMR. changes slightly.  [15]

## How will the height of the sound made by a circular saw change if the

How will the height of the sound produced by a circular saw change if you start sawing a thick board of dense wood on it?

Photo 40 from the presentation “Sources of sound” for physics lessons on the topic “Sound

Size: 352 х 352 pixels, jpg format. To download a free physics lesson photo, right click on the image and click “Save Image As. “. You can also download the entire “Sources of Sound” presentation with all the photos in a zip archive for free to show the photos in your lessons. Archive size. 1619 KB.

“Sound waves physics.”. Elastic medium. Gaseous. Sound waves. How We Hear. The Ear. Acoustics. Sources. Waves. Transverse. Perception of sound in animals. Threshold of Audibility. The standard tuning fork produces waves with a frequency of 440 Hz. Sensitivity of the ear to different frequencies. Physical: Resonance! Helmholtz. 20kHz. Feet.

“Ultrasound Physics.”. Ultrasonic waves can form highly directional beams. Domestic uses ( ultrasonic washing machines, range finders, t. ч. police radars, etc. д.). Ultrasonic waves affect the solubility of matter and, in general, the course of chemical reactions. Application of ultrasound. Ultra- and infrasound are common in nature.

Sound Propagation”. Infrasound is characterized by low absorption. This is why there is complete silence on the moon because of the lack of atmosphere. 1)Tone of sound. At 440 Hz, the hearing threshold is close to 10-12 W/m2. Ultrasound is widely used in science and technology. Practical part. What is sound? Properties of Sound. The crushing effect of ultrasound is used to make ultrasonic soldering irons.

“Sound”. Topic: Sound waves. A mosquito flaps its wings at a frequency of 10,000 times per second! Sound does not travel at lightning speed but at a finite rate. Sound waves are commonly referred to as waves that are perceived by the human ear. Speed of sound in metals, in steel. 5000 m/s. Speed of sound. Loudness depends on the amplitude of vibration in a sound wave.

“Sound Characteristics”. Answers: Why can we hear a flying mosquito but not a bird?? Answer the questions. А. In meters per second B. in seconds B. in Hertz D. in meters. 6. What is the approximate speed at which sound waves propagate in air? What are the characteristics of sound? The source of sound is V g a a d b. Lesson topic: 3. In what units is the speed of a sound wave measured?

“Sources of sound”. У. Number of vibrations per unit time. З. Decrease. Brass wind instruments. Any sounding body Wooden wind instruments. 3.The frequency of an oscillation is 2. The amplitude of an oscillation is F. Number of vibrations in some time. Г. The coordinate of an oscillating body. The timbre of a sound depends on the set of overtones.

## How to use a handheld circular saw secrets and techniques for proper and safe operation of a dangerous tool

The manual circular saw, like any other automatic hand tool, is a device whose use is associated with certain risks and dangers. First of all there is a real possibility of body damage by a sharp saw blade, in addition, the saw blade itself can behave inappropriately and cause injury.

### Saw Stop. This guy puts a finger into an active table saw blade & comes away without a scratch!

To avoid possible injury, we will present in this article all the rules and techniques for safe operation of the hand circular saw.

## Measure

The pitch of a sound is measured on a relative scale: octaves, within octaves. notes. Octave. is the musical interval corresponding to the ratio of frequencies of two sounds equal to 2. (That is, for a note of the same name in the next octave, the frequency expressed in hertz will be exactly 2 times higher than in the current octave).

Within an octave, the smallest musical interval. semitone (the musical interval between the two nearest notes in an octave, roughly corresponding to the ratio of frequencies of two sounds equal to. “Approximately,” because in nature, the notes within an octave are unevenly spaced (see. Pythagorean structure. comma).

Correspondence of notes in octaves to specific frequencies (in hertz) is given by standards.

Over the entire range of height values, they can be obtained by intervals between short pulses, such as single intensity counts in a discrete time t = ndt, where dt =22.7 µs.

A sound with a seemingly constantly rising or falling pitch. one type of acoustic illusion. is called the Shepard tone.

Frequency signals of complex Spectra without a fundamental frequency (the first harmonic in the spectrum) are called residual. Perception of the height of the frequency signal is the same as the perception of the height of the resistive version of the same signal.

## Alternating electrical current. Inductance in an AC circuit. Ohm’s law for a series circuit. page 13

The speed of sound depends on the elastic properties, density, and temperature of the medium. The higher the elastic force, the faster the transmission of particle vibrations to neighboring particles and the faster the propagation of the wave. Therefore, the speed of sound in gases is less than in liquids, and in liquids it tends to be less than

in solids. For comparison, let us give the speeds of sound in air, in water, and in iron at / = 20° C:

The speed of sound in ideal gases increases with increasing temperature as (7 = 273°-\-t° C. absolute temperature). In air the speed of sound o = 331. at t = 0°Cи v= 343. at t = 20 °C. The speed of sound in air was first determined in 1640. by French physicist Maren Mersenne.

Sound waves (especially ultrasonic frequencies) have very wide applications in science and technology. For example, they are used to connect tiny conductors in microelectronics, where traditional soldering is excluded, they are used in medicine for diagnostic purposes (so-called ultrasound scanners, which allow to examine the internal organs of man. Unlike the X-ray radiation, ultrasonic radiation is harmless to humans).

A method of orientation or research of surrounding objects, based on emission of ultrasonic impulses followed by their echo perception is called echolocation, and corresponding devices are called echolocators. The best known animals with echolocation capabilities are bats and dolphins. In their perfection, the echolocators of these animals are as good as, and in many ways superior to, modern man-made echolocators.

| Various cetaceans have this way of orientation, as well as guajaro birds nesting in deep caves in Venezuela and on the island of Trinidad, swifts and salagans living in caves in Southeast Asia.

Echolocators used underwater are called sonars or sonars (the name sonarformed from the initial letters of the three English words: sound, navigation.navigation, range). Sonars are indispensable for exploring the seabed (its profile, depth), for detecting and researching various objects moving deep underwater. They can easily detect individual large objects or animals, as well as packs of small fish or shellfish.

2 1. What is the nature and source of sound?? ‘ 2. How sounds are classified?

What range of sound frequencies can the human ear perceive??

What is the speed of sound in air?

What are the frequencies of infrasound and ultrasound?

What are the main characteristics of sound?

What is the threshold of hearing?? pain threshold?

At what frequency the human ear has the best sensitivity?

What are some examples of the uses of sound waves?

Which flaps its wings more often in flight: the fly or the mosquito??

Why does the sound pitch of a circular saw decrease when a board is pressed against it?

)/ ^Exercise 36

Distance between two railway stations / = 8.3 km. How long t is the sound traveling from one station to another through the air and along the rails? Air temperature f=0°C. The speed of sound propagation in steel ust =

\. Dolphins emit ultrasonic waves at a frequency of

v = 250 kHz. Determine the wavelength A, such sound in water and in air at f=20°C. 3. What is the depth of the sea H at a given location if the ultrasonic impulse returned after At = 0.20 s after it was sent? The velocity of ultrasound in seawater и =

Man sees heavy stone falling on concrete sidewalk. A short while later, he hears two thuds: one came through the air and the other spread out in the concrete. Time interval between them Af = 1.2 s. How far away / from the person fell the stone?

## Why does the sound pitch of a circular saw decrease when a board is pressed against it??

Journey with a sound wave Theme 3 “Sources of Sound” 3.1. This source of sound is invented for the option of musical instruments 3.2. What contributes to the volume of a guitar sound? 36. The housing has a definite shape with a hole in it. 3.3. This source of sound is named after the heroine of an ancient Greek myth, Honor 3.4. When a shock wave passes into sound vibrations? 39. At explosion, bullet flight, lightning 3.5. Can a student’s ruler be the source of a sound wave? 3.6. Which statement is true: 1) every sounding body vibrates; 2) every vibrating body sounds? 30. The first statement is correct. 31. The second statement is true 3.7. A race judge stands at the finish line. When he should start his stopwatch: when he sees the smoke of the starter pistol or hears the shot? 301. When seeing smoke. 302. When he hears a gunshot 3.7. Why does the sound pitch of a circular saw decrease when it is pressed against a board? 308. Saw speed decreases. 306. The rotation speed of the saw increases 3.9. What is called timbre? 300. Sound coloring depending on the sound source. 305. The coloring of the sound depending on the volume 3.10. Why we can’t talk on the moon? 311. No sound wave transfer medium. 318. We’ll be in a spacesuit 3.11. What are the benefits of seismic waves? 303. Helping to find an oil field. 316. Destroying old buildings

What is sound? 2. What is the cause of sound? 3. Name the physical characteristics of sound. 4. What frequency mechanical vibrations are called sound vibrations?? Sound pressure level, dB Leaves, surf The alarm clock chime The player The sound of an airplane engine Soothes Appears irritable, fatigue, headache 114 Causes alcohol-like intoxication, disrupts sleep, destroys the psyche, leads to deafness. Pain sensation 130 20 80 Violoncello Saxophone BALAYKA Why does a bullet fly out with a whistle when fired from a rifle, but a bullet thrown by hand flies silently? Why does the sound pitch of a circular saw decrease when a board is pressed against it? Which flaps its wings more often in flight: the fly or the mosquito? Which expression is always true: a) every sounding body vibrates; b) every vibrating body sounds. 2. How would the volume of a sound change if the amplitude of its source oscillations were reduced? a) will decrease; b) will increase; c) will not change. 3. What does the pitch of a sound depend on?? a) amplitude of vibration; b) frequency of vibration; c) speed of sound. 4. In what units is the volume of a sound measured? a) decibels; b) sleep; c) Hz. 5. What is the basic tone ? a) The quality that distinguishes sounds of some sources from sounds of others; b) The highest frequency of a complex sound; c) The lowest frequency of a complex sound. 1. Answers: 1a; 2a; 3b; 4b;5c. Homework 1)§35, 36, answer the questions for paragraphs. 2) (for those who wish to receive a “5”) Answer the question: “What is the difference between a major and a minor in terms of physics??”.

## Why, when a bullet is fired from a rifle, it comes out with a whistle, but when thrown

Why does a bullet fired from a shotgun whistle, but a bullet thrown by hand fly silently?? Why does the height of sound of a circular saw decrease when a board is pressed against it?

Slide 7 from the presentation “Loudness and pitch of sound” for physics lessons on “Sound

### Skill saw circular saw bearing replacement

Size: 960 x 720 pixels, format: jpg. To download a free slide for use in a physics lesson, right click on the image and click “Save Image As. “. Download the entire presentation “Loudness and pitch of sound.ppt” can be found in the 721 KB zip archive.

“Sound Reflection.”. 1. What is the speed of sound in air? А. 300 m/s B. 340 m/s In. 440 m/s D. 500 m/s. Sound test. 3. A sound wave in air is: Reflection of sound”. А. Increases B. Does not change C. Decreases D. It changes in a wave-like manner. 2. How does the speed of sound change as the density of the medium decreases?

“World of Sound.”. Application of sound waves: Ultrasounds and infrasounds have a very important role in the living world as well. The oscillation of the needle left a sound track on the roller. Biological acoustics deals with the sound and ultrasonic communication of animals. Nature, in endowing living creatures with hearing, has shown considerable ingenuity.

“Sound.”. Frequency spectrum of musical instrument sounds. Man lives in a world of sound. The strongest vibrations will be observed at the ends of the plug. Objectives: 1. Introduce the concept of sound waves. A mosquito flaps its wings at a frequency of 10,000 times per second! CHARACTERISTICS OF SUMMER Loudness. The lower end oscillates at the same time. foot of the tuning fork.

“Ultrasound and infrasound physics”. General acoustics studies the emergence, propagation, and absorption of sound. Audibility diagram of sounds. MOO SOSH 1. Sound is created by long-lasting periodic sound sources. Done by: 11th grade student M. Gauck.А. Among periodic oscillations, harmonic oscillations play a very important role.

“Infrasound.”. This was followed by an indecipherable series of dashes and dots, and then the distinct, “I’m dying.”. The organ can reproduce infrasound. The natural (resonant) frequencies of some parts of the human body. Many rushed to the exit. The specific effects of infrasound on humans led to the idea of creating infrasound weapons.

“Sound Characteristics.”. А. in meters per second B. in seconds C. in hertz D. in meters. Volume of sound Height of sound Timbre of sound. 6. What is the approximate propagation speed of sound waves in air? Answers: Why can we hear a flying mosquito, but not a bird?? Answer the questions. Lesson topic: Frequency of wings of insects and birds in flight, Hz.

## Presentation on: Loudness and pitch of sound

No. of slide 1

Knowledge Update What is sound? State the causes of sound. What are the physical characteristics of sound? Mechanical vibrations of which frequencies are called sound? 900igr.net

No. of slide 3

Sound pressure level, dB Leaves, surf 20 Soothes Clock chime 80 Induces irritation, fatigue, headache Walkman 114 Causes alcohol-like sound intoxication, disturbs sleep, destroys psyche, leads to deafness. Airplane engine sound 130 Pain sensation

No. slide 7

Why does a shot from a gun make a whistling sound and a hand-thrown bullet fly silently?? Why does the pitch of a circular saw decrease when a board is pressed against it??

Who flaps its wings more often in flight: a fly or a mosquito?

No. of Slide 9

Which expression is always true: a) every sounding body vibrates; b) every vibrating body sounds. How does the volume of a sound change if you decrease the amplitude of its source? a) will decrease; b) will increase; c) will not change. 3. What does the pitch of the sound depend on?? a) amplitude of vibration; b) frequency of vibration; c) speed of sound. 4. In what units is sound volume measured? a) decibels; b) sleep; c) Hz. 5. What is a fundamental tone? ? a) The quality that makes it possible to distinguish the sounds of some sources from those of others; b) The highest frequency of a complex sound; c) The lowest frequency of a complex sound. Answers: 1a; 2a; 3b; 4b;5c.

No. slide 11

Homework 1)§35, 36, answer the questions to the paragraphs. 2) (For those who want to get an “A”) Answer the question: “What is the difference between a major and a minor in terms of physics??”.

## Presentation, report on Loudness and pitch of sound

What is sound? State the reasons for the origin of sound. State the physical characteristics of sound. Mechanical vibrations of what frequencies are called sound?

Why does a bullet fired from a rifle make a whistling sound, but a bullet thrown by the hand flies silently??

Why does the pitch of a circular saw decrease when a board is pressed against it??

Which flies more often: the fly or the mosquito?

Which expression is always true: a) every sounding body vibrates; b) every vibrating body sounds. How would the loudness of a sound change if the amplitude of the vibration of the sound source were decreased?? a) will decrease; b) will increase; c) will not change. 3. On what does the pitch of a sound depend? a) amplitude of vibration; b) frequency of vibration; c) speed of sound. 4. In what units is the volume of a sound measured? a) decibels; b) sleep; c) Hz. 5. What is pitch? ? a) The quality which distinguishes one sound source from another; b) The highest frequency of a complex sound; c) The lowest frequency of a complex sound. Answers: 1a; 2a; 3b; 4b;5c.

1) §35, 36, answer the questions to the paragraphs. 2) (for those who want to get an “A”) Answer the question: “What is the difference between a major and a minor in terms of physics??”.

## Lesson project “Sound, timbre, and volume.

Please note that in accordance with Federal Law N 273-FZ “On Education in the Russian Federation” in organizations carrying out educational activities, training and education of students with disabilities is organized as a joint with other students, and in separate classes or groups.

Development of controlling functions of the child’s brain: useful tips and exercises for teachers

A certificate and a discount for each participant

### Select a document from the archive to view:

Selected to view document Physics Lesson in 9.doc

Physics lesson in 9th grade “Loudness and pitch”

Lesson Objective: To study the basic characteristics of sound waves.

1. Educational. To evoke an objective need for future activities; to promote the mastery of the knowledge of “Loudness and pitch of sound”.

2. Development. Development of the outlook, analytical abilities, to promote the development of speech, thinking, cognitive and general skills;

3. Educational. Continuation of forming skills of public speaking, searching for information and methods of work with information.

Equipment: computer lab, Digital Learning Resource “Pitch and Tone of Sound. Sound Volume” from the Common Collection of Educational Resources, Tuning fork with a mallet, multimedia projector, digital teaching materials, metal ruler, Chaliapin and Pavarotti soundtracks.

Setting a goal for the lesson, motivation 6 min

Learning of new material. 20 min

Volume level and its effect on the human body.

Reflection and homework 4 min

Hello! It’s nice to see you in class again.

Teacher’s introduction: something from yourself.

Let’s review the material that will come in handy today (Slide 1).

3 stage. Setting the goal of the lesson, motivation

Now let’s do the following experiment.

Experiment with the tuning fork. Hit the tuning fork not hard, the second time hard.

How these sounds differ? (Students’ answers.)

Loudness is a physiological characteristic of sound, and what physical characteristic is related to loudness? Think about it and write your answer on the worksheet.

Fragments of works by Chaliapin and Placido Domingo are played.

Why do singers’ voices sound different?? (Students’ answers)

The pitch of the sound. This is also a physiological characteristic. Which physical characteristic is responsible for the pitch of the sound? (Students’ answers (guesses) are written on the worksheet.)

There is another characteristic of sound which is called timbre. What do you think it is?? (Write your hypothesis on the worksheet)

What do you think is the topic of our lesson and its purpose? (Students’ answers.). The topic of the lesson “Height and loudness of sound” appears on the screen. (Slide 2)

(After 10 minutes, there is a test of the work in pairs. Listening to the results of the pairs’ work.)

If there is no Internet connection and no computers, the class is divided into 3 groups. Each group is given a text card to learn one of the characteristics of a sound, learn how to demonstrate them, and speak in front of the class. If the class is strong, we can give the text from the textbook and choose the instruments we want to demonstrate, if not, we can give an adapted text (below) and a ready-made set of instruments.

Now let’s move on to a discussion of the characteristics of sound. The first is the pitch of the sound. The pitch of a sound a characteristic which is determined by the frequency of the vibrations. The higher the frequency of the oscillating body, the higher the sound will be. Let’s look again at the ruler in the vice. As we said, we have seen the vibrations, but we have not heard the sound. If we now make the length of the ruler shorter, we will hear the sound, but it will be much harder to see the vibrations. Look at the ruler. If we play it now, we won’t hear a sound, but we will see a vibration. If we shorten the ruler, we will hear a sound of a certain pitch. We can make the length of the ruler even shorter, then we will hear a sound of even higher pitch (frequency). We can observe the same with tuning forks. If we take a big tuning fork (also known as a demonstration tuning fork) and hit the legs of this tuning fork, we can observe an oscillation but we will not hear a sound. If we take another tuning fork and hit it we hear a certain sound. And the next tuning fork, a real tuning fork, is used to tune musical instruments. It produces a sound that corresponds to the note in A, or 440 Hz, as they say.

The next characteristic is the timbre of the sound. The timbre is called the coloration of the sound. How we can illustrate this characteristic? The timbre is the difference between two identical sounds made by different musical instruments. You all know that we only have seven notes. If we hear the same note “A” taken on the violin and on the piano, we will distinguish between them. We can tell at a glance which instrument made the sound. This is a characteristic of the timbre, the coloring of the sound. It must be said that the timbre depends on which sound vibrations are reproduced, in addition to the basic tone. The fact is that arbitrary sound vibrations are quite complex. They consist of a set of individual vibrations, they say Spectra of vibration. It is the reproduction of the additional vibrations (overtones) which characterize the beauty of the sound of a voice or an instrument. The timbre is one of the main and striking manifestations of sound.

Another characteristic is loudness. The loudness of the sound depends on the amplitude of the vibrations. Let’s look and see how the loudness is related to the amplitude of the vibrations. So let’s take a tuning fork. Let’s make the following: if you strike the tuning fork lightly, the amplitude of the vibrations will be small and the sound will be soft If you hit the tuning fork harder now, the sound is much louder. This is because the amplitude of the vibrations will be much greater. Perception of sound is a subjective thing, it depends on what kind of hearing aid, what kind of human well-being.

### How loud are my power tools?

The children’s speeches. (Summary on slide 4)

Now back to your assumptions. On the worksheet, under the line, write down the correct answers to the question: on what magnitudes do the pitch and volume of sound and the timbre depend? Raise your hands if you’ve guessed correctly? Very good! (Students raise their hands.)

You have metal rulers on your desks, use them to get the highest sound and at the same frequency the loudest and quietest sound (students demonstrate).

In problem books, in the passports of acoustic devices to characterize them, instead of sound volume, it is customary to use the volume level measured in backgrounds or sound pressure level measured in whites and decibels. (Slide 4).

Let’s look at the table. What sounds create what level of sound pressure and how they affect the body with prolonged exposure. 40 decibels is considered normal.

When comparing sounds of different frequencies, you must take into account the following factor that affects loudness. The reason is that the human ear is differently sensitive to different frequencies. Therefore, if the amplitudes are the same, we perceive sounds with frequencies between 1,000 and 5,000 Hz as louder. The loudness of a sound also depends on the length of time it is heard and on the characteristics of the individual listener. To amplify the sound use the following simple devices: horn, loudspeaker, phonograph.

Let’s try to apply our knowledge by answering a series of questions.

Now let’s test your knowledge from this lesson.

How would the loudness of a sound change if you decrease the amplitude of its source?

In what units is sound volume measured?

a) the quality that allows you to distinguish the sounds of some sources from the sounds of others;

b) the highest frequency of a complex sound;

6 stage Reflection and homework. (Slide 10)

For each letter of the word SOUND, name an association that occurs to you in this lesson. (Answers of pupils).

Paragraphs 35, 36, answer the questions to paragraphs.

(For those who want to get an “A”) Answer the question: “What is the difference between a major and a minor in terms of physics?”.

Thank you for the lesson! It was a pleasure working with you.

Peryshkin A.В. Physics. 9kl.Textbook for General Education. institutions/ Peryshkin A.В., Е. М. Gutnick 13th ed., Drofa М. : Drofa, 2008.

## Proper sawing techniques at home

It is important to use the appropriate disc. For stationary machines longitudinal saw blades differ from cross saw blades, the shape of the tooth and the sharpening angle. For manual circular saws there is no such basic division. You can use one disk for sawing lengthwise and crosswise.

Longitudinal and cross-cutting saw blades must be “rare toothed” with 12 to 24 teeth, depending on blade diameter and model. Blades with small, frequent teeth are designed for clean cutting, but they cut slowly and overheat on a long rip.

Disc thickness depends on the workpiece. Thin blade slices faster, less wood is selected, and the load is reduced. But a thin disk can overheat, turn blue, lose its hardening and fail on thick hardwood workpieces. Also thin saw blades tend to move away from the marking, “wiggle” the kerf.

In contrast to stationary circular saws with motors up to 5 kW (10 kW and more on industrial ones) and considerable inertial acceleration of the shaft, electric hand saw has smaller power reserve. That’s why they slow down and do not overheat the engine or decrease RPM.

### At 90 and 45 degrees

All manual circular saws have the ability to tilt the platform. Due to that an angle of 90 to 45 degrees is possible. On some models and at a steeper angle.

Setting the right angle is simple: the screw is released, the desired angle is set on the arc with degrees, the screw is locked. It must be remembered, however, that the maximum cutting depth is reduced when sawing at an angle. For example, if at a right angle it is possible to saw a billet 60 mm thick completely, then at an angle only 45 mm.

Cutting at an angle is more difficult because the blade cuts the wood fibers also at an angle, which increases friction and resistance. The teeth of the disk should be sharpened, because otherwise the wood could burn or turn black. Otherwise, sawing at an angle is carried out in the same way as the above-described direct sawing.

### Bar 150×150 and 100×100 lengthwise

Depth of kerf manual circular saws does not allow you to cut a material thickness of 10-15 cm. The maximum for most models is 60-75 mm. However it is possible to cut a 100×100 and even 150×150 timber along its length by making two cuts from the opposite sides.

The cut is made along the guide rail, just like when cutting a sawn board. Then the bar is turned over 180 degrees and make the second kerf. In this case, an unevenness is sure to appear at the joint of kerf. This cannot be avoided.

Even if the bar is straight and the kerf is precisely guided. 1-2 degrees of deviation of opposite surfaces of the timber is enough, and there is unevenness at the joint of kerf. And such deviations are inevitable, even with lint on the wood.

Problems with this type of sawing: the saw blade is fully enclosed in the solid wood, the tooth tips do not protrude or cool in the open air, the saw blade friction is everywhere, and sawdust is difficult to eject. Therefore there is a high probability of overheating of the disk and the engine.

It is best to make a sawmill from a chainsaw for such tasks, the costs are small, and the result is good, especially the cutting accuracy and performance.

Sawing is done intermittently, making sure that the blade and motor do not overheat. Such sawing does not fit the manual circular saws’ purpose and is done on sawmills or stationary circular saws. If necessary, it is possible to saw several large cross-section bars, but the manual circular saw can not operate for a long time in this mode.

### Laminated chipboard and chipboard without chips

For sawing laminated chipboard (Laminated Particle Board), as well as wood-fibre board, special machines with an additional scoring blade are used. In the absence of such a machine in the home workshop, you can use the principle of its operation and saw the sheets with a regular circular saw.

The principle of undercutting disc operation: it makes a shallow cut of 1-1.5 mm in the cladding, and it rotates in the opposite direction. The main disc then completes the cut. Craftsmen have tried sawing Laminated Chipboard with conventional manual and stationary circular saws using the same principle, as follows:

• With the position of the support platform, the cutting depth is set at 1-1.5 mm.
• Make the kerf so that the saw blade cuts backwards. Turn the manual circular saw “backwards”; on a stationary circular saw the sheet is turned from the other side.
• After sawing the cladding the plate is finished in the usual way, on the same side that was used for the shallow cut. In this case the depth of cut is set so that the disc goes out of the sheet to the height of the tooth.

The method may not be suitable for some types of laminate. For example the “vitreous” surface on old Soviet furniture is not sawed in the same way as a more resilient laminate. Therefore it is advisable to make a test cut on an unnecessary workpiece.

There are other ways to saw without damage.

• Tape or self-adhesive tape over the kerf. The adhesive tape holds the edges of the laminate when you are sawing and prevents pieces of the surfacing from tearing off. The method does not always work, it depends on the type of laminate, the disk, the speed.
• The future kerf is drawn by cutting through the laminate with a sharp tool. The method can help if you manage to cut through the cladding and then run the blade exactly along the place of the cut.

### Plywood without chips

Plywood tears out from underneath the kerf. This is because when the tooth pressure is applied from above, the plywood particles are held back by the lower layers of the sheet. But the lower layer of plywood holds nothing back and can have rips and chips on it. This can be avoided by sawing in exactly the same way as described above for laminated sheets Woodchipboard and Fibreboard.

It is advisable to use a universal or special disk with small, frequent teeth. they create a more even load than the rare toothed discs, and therefore the possibility of chips is less.

If the circular saw has a RPM adjustment function, set it to maximum. The higher the speed of the saw blade, the less it tears the material.

### Log to board

Sawmills are designed for sawing logs. You can dissolve a small number of logs with a diameter of 15-20 cm with a circular saw in case of emergency.

To do this, the two opposite sides of the log is removed from the review or sawed slab (with an axe, circular saw with a large disc, chain saw, a powerful fugark) so that the surfaces were flat, like a beam. As a result, you get lafet or plaque, which looks like a thick unedged board, or a beam trimmed on both sides.

Then the material is sawn in the same way as a 100×100 or 150×150 beam described above.

The operation is labor-intensive and time-consuming. In this case, the correct geometry of the board is difficult to obtain, and the tool is highly overloaded.

### How to cut a half-timbered board?

Trimming a board with a manual circular saw can be done in two ways:

• According to the markings with a pencil (a marker, a sharp tool, etc.) the material is cut.д).
• On a guide rail. For this purpose, a bar, angle or factory guide rail is attached to the board with screws or self-tapping screws. Sawing is done by pressing the edge of the saw’s platform against the guide rail.

Sawing along a guide will usually give a smoother cut.

We also recommend reading a helpful article with reviews of the most popular and best circular saws for the home.

## Characteristics of sound 500

Characteristics of Sound 500. Why does the sound pitch of a circular saw decrease when a board is pressed against it? Check.

Picture 57 from the presentation “Sound Quiz” for physics lessons on “Sound”

Size: 286 x 359 pixels, format: png. To download a free physics lesson picture, right-click on the image and click “Save Image As. “. You can also download the “Sound Quiz” presentation for free to show the pictures in class.ppt” as a whole with all pictures in zip-archive. Archive size. 3011 KB.

“Sound vibrations physics.”. Sound vibrations. Sound frequencies. Sound phenomena. Properties of sound. The meaning of sound. В 1700. 1707. Joseph Sauveur’s memoirs on acoustics, published by the Académie des Sciences de Paris, came out. Physics, 9th grade Compiled by: teacher Kuleshova S.Е. The world around us can be called the world of sounds.

“Vibrations of sound. The “Do” sound (fig. 1) by a normal keystroke. Height. Determined by the frequency of vibration, from 15 to 20,000 Hz. On sweeps, overtones appear as deviations from the frequency of the main tone. and the method of doing the work. Let’s produce and record the “Si” sound of another octave (Fig.5) and is comparable to (fig.3) by frequency.

“The World of Sound.”. Noises. What is the sound? Ultrasounds and infrasounds are also very important in the living world. Acoustics. science of sound. Mechanical noises can be caused by the vibration of solids. How some sounds differ from others? Nature has shown great ingenuity in endowing living creatures with hearing. Hearing acuity is greatest at ages 15 to 20.

“Speed of sound propagation.”. In liquids, sound travels faster. Experimental confirmation. The speed of sound. What is called a pure tone? What is the effect of systematic exposure to loud noises on human health?? Sound waves. How is the pitch of a sound determined?? Propagation of sound. How is the timbre of a sound determined?? The speed at which sound waves propagate in different media is not the same.

“Characteristics of Sound”. The source of the sound is Frequency of wingbeat of insects and birds in flight, Hz. Volume of a sound Height of a sound Timbre of a sound. Frequency range of singers and singers, Hz. Why can we hear a flying mosquito, but not a bird? 6. What is the approximate speed of propagation of sound waves in air? Sound Characteristics.

“Loudness and pitch of sound”. Placement test. What is sound? Mechanical vibrations of which frequencies are called sound? Loudness and pitch of sound. Knowledge Update. Saxophone. What are the physical characteristics of sound? Cello. Whether a fly or a mosquito flaps its wings more often in flight? Balalaika. What is the origin of sound?

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