Sound - Energy or Wave

SOUND

Sound is a form of energy, sound  propagates when  molecules ( air molecules)  vibrate and move in a pattern called waves, or sound waves.

Sound needs a medium ( by the help of molcules) to propagate. The matter or material through which sounds propagates is called a medium. Sound cannot travel in a vacuum. The moon does not have an atmosphere , no sound can be heard here.

Rainbow 🌈 mind map

Production Of Sound:

• The sound is produced by vibrating objects. NO vibration NO sound.
• They travel from one place to another in the form of waves. 

Different ranges of sound:

• Audible range = 20Hz to 20kHz known as the Sonic range 
• Below 20 Hz (inaudible) → infrasonic range
• Above 20 kHz (inaudible) → Ultrasonic range

Sound in different media:

sound  travels most quickly through solids, followed by liquids, and then by gases.

They are molcules of matter helping sound to move from one place to another Molcules of matter are closest together in solids and farthest apart in gases.That is why speed of sound maximum in solids and least in gas

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Sound as longitudinal wave:

A sound wave is an example of a longitudinal wave and is produced by the vibrations of the particles that travel through a  medium. An example of sound wave is by  the tuning fork.

Sound wave comprises Compression and rarefraction

In a longitudinal wave, compression is a region in which the particles of the wave are closest to each other.

Rarefaction in a longitudinal wave takes place when the particles are farthest apart from each other.

Characteristics of Sound:

Unit of Loudness of Sound:

sound intensity that is loudness of sound is measured in unit called decibels. decibels (dB) is  named in honor of Alexander Graham Bell, the inventor of  the telephone .

Speed of sound on different media: 

Speed of sound is minimum in air and maximum in solids 

Learn more:-

1. Wave: Wave is a disturbance in which energy is transferred from one place to another.

There are two types of mechanical waves:

• Longitudinal waves – In this type of wave, the movement of the particle are parallel to the motion of the energy i.e. the displacement of the medium is in the same direction to which the wave is moving. Example – Sound Wave

• Transverse waves –  When the movement of the particles is  perpendicular to the motion of the energy, then this type of wave is known as Transverse wave.  .
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2. Terms related wave:

Amplitude (A): The amplitude of a wave is the maximum displacement of any particle of the medium from its mean  position.

Period (T): Period (T) of a wave is the time taken by any particle of the medium to complete one vibration .

Wavelength (λ): Wavelength (λ) - It is equal to the distance travelled by the wave by its time period (T).

Frequency (f): It is the number of vibrations made per second by any particles of the medium

 f = 1/T

3. Factors affecting Pitch of musical instruments:

4. Relation between Amplitude and Loudness:

Amplitude increases , loudness increases

Loudness is directly proportional to square of Amplitude . Amplitude increases two times loudness will increase 4 times

5. Relation between Frequency and Pitch:

Frequency increases, Pitch increases. 

Frequency increases by 2 times, Pitch will be also doubled

6. Monotone by tuning fork:

7. Noise and music:

Know more:-

1.Why does the sound of water change as a bucket is filling from empty to full?

Answer:- Pitch of sound increaeses with in air column so pitch of sound will go increasing as a bucket is filling from empty to full.

2.Does sound Reflect? If yes where is the  reflected sound?

Answer:-  The reflected sound is called Echo. 

The necessary conditions for hearing an echo is  the distance between the sound source and the place ( wall, mountain etc) from where it is reflected  must not be less than 17 m because the time between hearing the original sound and its echo (reflected sound)  should not be less than 0.1 of a second to get distinguished.

Students corner:

Abhilasha Jha 

Arpita Mishra 

Author
Ritu