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VR Tour For Std. 9 Ch. 12. Sound

What's Included in Virtual tour of this chapter

A sound is a form of energy that produces a sensation of hearing in our ears. Sound is produced by vibrating objects. And this vibrating object produced some waves. Amplitude, Wavelength, Frequency, Time period, Velocity, Pitch are the characteristics of sound waves. When the speed of any object exceeds the speed of sound it is said to be traveling at supersonic speed. Bullets, jet aircraft, etc. often travel at supersonic speeds. When we hear the same sound again and again in a medium it is called Echo. Further, in the virtual tour, we will understand how Ultrasound is used to clean machine parts located in places that are not easily accessible.

Virtual tour 1 Sound and its propagation

Virtual tour 1: Sound and its propagation

Sound is produced due to the vibration of objects. Vibration means a kind of rapid to and fro motion of an object. The sound of the human voice is produced due to vibrations in the vocal cords. Sound is produced when an object vibrates, that is they move in a ‘to-and-fro’ motion. Sound propagates in a medium as the particles of the medium vibrate from a starting point. 

Virtual tour 2 Sound waves and longitudinal waves

Virtual tour 2: Sound waves and longitudinal waves

On the basis of the direction of propagation, waves are categorized into two parts: Longitudinal waves and Transverse waves. Sound waves are longitudinal because the particles of the medium vibrate in the direction which is parallel to the direction of the propagation of the sound waves. The particles in the medium oscillate to and fro in the case of longitudinal waves. 

Virtual tour 3 Characteristics Of Sound wave

Virtual tour 3: Characteristics Of Sound wave

In this virtual tour, we will understand the wavelength, time period, frequency, and pitch of the sound. The distance between two consecutive compressions or Rarefaction is called Wavelength. The time taken to complete one vibration is called the time period. The number of vibrations per second is called frequency. Pitch represents shrillness or flatness of sound. It depends on the frequency of vibration.

Virtual tour 4 Sonic boom

Virtual tour 4: Sonic boom

A sonic boom is a loud sound kind of like an explosion. It’s caused by shock waves created by any object that travels through the air faster than the speed of sound. Sonic booms create huge amounts of sound energy. When an object moves through the air, it creates pressure waves in front of and behind it.

Virtual tour 5 Echo

Virtual tour 5: Echo

The phenomenon of hearing back our own sound is called an echo. It is due to the successive reflection of sound waves from the surfaces or obstacles of large size. To hear an echo, there must be a time gap of 0.1 seconds between the original sound and the reflected sound. The minimum distance of the obstacle from the source of sound must be 17.2 meters.

Virtual tour 6 Reverberation

Virtual tour 6: Reverberation

When a sound source ceases in space, the sound waves will continue to reflect off the hard wall, floor, and ceiling surfaces until it loses enough energy and dies out. The prolongation of the reflected sound is known as reverberation. We observe such phenomenon usually in an auditorium or big halls.

Virtual tour 7 Reflection of sound

Virtual tour 7: Reflection of sound

Megaphones, stethoscopes, and auditorium rooms are designed in such a way that sound can travel in a particular direction only without spreading out everywhere. This makes it easier for the audience to listen to the speaker. All these instruments work on the phenomena of multiple reflections of sound.

Virtual tour 8 Ultrasound

Virtual tour 8: Ultrasound

Ultrasounds are able to travel along well-defined paths even in the presence of obstacles. Ultrasounds are used extensively in industries and for medical purposes. Ultrasound is generally used to clean parts located in hard-to-reach places, for example, spiral tubes, odd-shaped parts, electronic components, etc.

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