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Table Of Contain-sound(ध्वनी)-mpsc science
Intro of sound(ध्वनी)
➤ Hence, the sound is a wave.
➤Sound is defined as vibration propagated through air or other media as audible mechanical waves
➤ It is made of vibrating objects
➤ The vibrating body vibrates the surrounding medium (water, air, etc.) to generate sound.
➤ speed of sound in dry air at 20 °C =343 m / s.
➤ sound travels most slowly in gases, faster in liquids, and faster still in solids.
➤ 1,481 m/s in water (almost 4.3 times faster) and at 5,120 m/s in iron (almost 15 times faster)
➤In diamond, sound travels at 12,000 meters per second (39,000 ft/s),— about 35 times its speed in air
how human produce sound
➤ Human beings have a voice box or larynx which is present in their throat on the upper side of the windpipe.
➤ The larynx has two vocal cords which have a narrow slit between them so that air can pass through it.
➤ As the lungs throw the air out of the windpipe, it passes through the slit and hence allows the production of sound as the vocal cords start vibrating.
➤ The vocal cord muscles also play a role in the production of sound.
➤ Their thickness and tightness describe the quality or type of the voice a person has.
➤ The vocal cords in males are of length 20 mm and females have 15mm long vocal cords.
➤ Children, on the other hand, have very short length vocal cords.
➤ Hence, the voices, their quality and their type are always different in women, men and children.
Propagation of sound through a medium
➤Sound always requires a medium to travel from the source of its production to the receiver end.
➤Different mediums of propagation of sound are air, liquid and solids.
➤ Sound cannot travel through a vacuum as it lacks any medium of transmission.
➤ Sound needs some vibration of molecules to travel.
➤ Solids, liquids and gases all have molecules present in them which allow the propagation of sound.
➤ These molecules or particles in solids, liquids and gases are packed in varied ways.
➤ Solids have tightly packed particles in them and hence they allow fast propagation of sound through them as the vibrations can be carried easily from one particle to another.
➤ Liquids have slightly loosely packed particles and hence it takes a little time for sound to travel in water or through a liquid.
➤ Gases have completely loosely packed particles and hence sound takes the most time in traveling through the air.
➤ Sound through water travels 4 times faster than through the air.
➤ Sound through solids travels 13 times faster than through the air.
How do we hear
➤We know that sounds are produced as waves in the air or any other medium.
➤ As these sound waves travel to our ears they convert them into electrical signals or messages that our brain can understand.
➤ Our ears have a special structure that allows this function.
There are three major parts of the human ear
1.The outer ear (Pinna):
➤ It catches the sound waves and forwards them to the next part of the ear, that is, the middle ear.
2.The middle ear:
➤ It converts the sound waves into vibrations that then travel to the inner ear.
➤ It can do this with the help of the eardrum.
➤ The eardrum is a thin rubber-like sheet present in the Middle ear.
➤ As the sound waves reach the eardrum, it vibrates and these vibrations propagate to the inner ear.
3.The inner ear (cochlea)
➤ It receives the vibrations sent by the eardrum.
➤ It contains a liquid substance and the vibrations that enter the inner ear moves through this liquid.
➤ There are tiny hairs present inside the inner ear that turn these vibrations into signals for the brain and pass them to the brain through the hearing nerve.
➤ As the brain receives the signal it interprets the sound.
➤ However, this whole process is so quick that we cannot notice it.
The loudness of a sound
➤The loudness of a sound depends upon the amplitude of the sound.
➤ The higher the amplitude, the higher is the displacement of the particles and the higher is the loudness of the sound.
➤ The loudness of the sound is directly proportional to the square of its amplitude.
➤ The SI unit for measuring the loudness of a sound in decibels (dB).
➤ In the International System of Units, the unit of power is the watt, equal to one joule per second.
➤ In older works, power is sometimes called activity. Power is a scalar quantity.
➤ SI unit: watt (W)
➤ There are two types of waves
➤ 1.Transverse wave and 2. Longitudinal waves
➤ Transverse wave: is a moving wave whose oscillations are perpendicular to the direction of the wave or path of propagation
➤ Longitudinal waves: the particle displacement is parallel to the direction of wave propagation
➤sound waves are the Longitudinal waves.
Pitch of the sound
➤ Every person has a different sound quality.
➤ Also, every musical instrument vibrates to produce a different kind of sound.
➤ This quality of sound is characterized by its Different quality of sounds may have same pitch and loudness.
➤ The pitch of a sound depends upon the frequency of the sound wave.
➤ The pitch would be higher if the frequency of the sound is high.
➤ Vibration can be described as a back and forth motion of an object.
➤ Depending upon the vibrations, a sound is produced. Sound cannot be produced without any vibration.
➤ The sounds having a frequency range below 20 hertz are called infra sound
➤ Infra sound cannot be heard by humans.
➤ Infra sound waves are used to treat myopia in kids
➤ 0 to 20 dB
➤ Normal hearing ranges from 0 to 20 dB in all frequencies
➤ he sound waves having a frequency range above 20 kilohertz are called ultrasounds.
➤ Having too high frequency, they cannot be heard by human beings as well.
➤ Bats, dogs and cats use ultrasounds to communicate.
➤ Ultrasounds can be used for various purposes such as identifying abnormalities in the human body or calculating distances under the water through SONAR.
➤ a repetition of sound produced by the reflection of sound waves from a wall, mountain, or other obstructing surface. a sound heard again near its source after being reflected. any repetition or close imitation, as of the ideas or opinions of another. a person who reflects or imitates another.
➤ When the sound or signal is reflected and causes a large amount of reflection accumulation, and then attenuates as the sound is absorbed by the surface of objects in the space (including furniture, people and air), reverberation or reverberation occurs.
➤ SONAR stands for SOund NAvigation Ranging
➤ An ultrasonic beam is generated, and the ultrasonic beam is propagated through the seawater transmitted by the transducer. Whenever it reflects an echo, the sensor detects and records the echo. Then we are converted into electronic annunciators.
➤ 1.Active SONAR-It involves the emission of sound waves and waiting for the echo to return.
➤ It has a receiver and transmitter.
➤ 1.PASSIVE SONARInvolves listening to sounds produced by underwater objects
➤ It only has a receiver.
➤ Noise can be regarded as an unpleasant sound. Noise consists of sound waves of varied frequencies which have no particular periodic pattern of repetition.
➤ Therefore, noise is regarded as a mixture of sound waves with irregular frequencies.
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