Sound Important Points Study Notes previous year asked questions

Sound Important Points: Hi Viewers in this post us are sharing the Information of the Sound. In general physics one of the most important topics is sound. Questions from the topic Sound wave can be seen in the all competitive exams. Those who are seriously preparing for the Railway, Staff Selection Commission written examination sound study notes is very useful for your preparation. Don’t Neglected to prepare this topic if you are preparing for government exams. Below this post having some previous year asked questions in different exams.   

Sound Important Points Study Notes

Sound Important Points Study Notes previous year asked questions

Definition of Sound:

Sound is defined as vibrate the travel through the air or any other medium and can be here by human ear or animals ear that is called sound.   

Sound waves are longitudinal mechanical waves.

Sound waves are produced by compression and rarefaction of the particles of the medium.

Sound needs a medium to travel.

The speed of sound is the maximum in solids, less in liquids.

Sound waves are reflected, refracted, and diffracted, and exhibit interference.

Study of sound is called Acoustics.

Measurements of sound are Decibels (DB).

Sound cannot travel through vacuum.

Sound Travel with a speed of 332 m/s at 0 C. 

The speed of propagation of the sound waves is dependent on the wave frequency. 

According Their Frequency Sound Waves are classified into three types those are

Audible or Sound Waves

Infrasonic Waves

Ultrasonic Waves

Audible or Sound Waves

The Longitudinal Mechanical waves frequencies range is 20 HZ to 20000 HZ (200 KHZ) are called audible waves. These are sensitive to human ear.

Infrasonic Waves

The Longitudinal Mechanical wave’s frequencies range is below 20 Hz is called Infrasonic Waves.

Uses/ Applications of Infrasonic waves


Monitoring activities of the atmosphere

Forecasting natural disasters

Ultrasonic Waves

The Longitudinal Mechanical wave’s frequencies range is greater than 20000 Hz is called Ultrasonic Waves. Humans cannot hear the sound of inaudible range.

Application of Ultra Sonic Waves

Measuring Depth of Sea

For removing lamp-shoot from the chimney of factories

Sending Singles

In Ultra-Sonography

Cleaning cloths, aero planes and machinery parts of clock

Loudness of Sound
Normal Breathing
10 DB
Soft Whisper
30 DB
Normal Conversion
60 DB
Busy Traffic
70 DB
Telephone Dialing
80 DB
90 DB
Hand Drill
98 DB
Jet Engine
140 DB

Speed of Sounds in Solids

In a medium, speed of sound basically depends upon elasticity and density of medium.

Speed of sound (In m/s)
Carbon dioxide
Air (0 C)
Air (20 C)
Steam (100 C)
Water (20 C)
Sea Water

What are the characteristics of Sound Waves?

Sound Waves having mainly three characteristics like as Intensity, Pitch and Quality

It is defined as amount of energy passing normally per unit area.
SI Units of Intensity is Watt/m2.

Pitch is the characteristics of sound which distinguishes a sharp sound from grave sound.
It depends upon frequency.

It is the characteristics of sound which enables us to distinguish between sounds produced by two sources have the same intensity and pitch.

What is Echo?
The sound waves received after being reflected from a high tower or mountains is called echo.

To hear echo, the minimum distance between the observer and reflector should be 17m (16.6 m).

Persistence of ear (effect of sound on ear) is 1/10.

What is Match Number?

It is defined as the ratio of speed of sound source to the speed of sound in the same medium under the same condition of temperature and pressure.

Match Number > 1
Body is called supersonic
Match Number > 5
‘’’            ‘’’’’’    Hypersonic
Match Number < 1
‘’’’          ‘’’’’’    Subsonic speed

What is shock Wave?
Shock wave is defined as body moving with supersonic speed in air leaves behind it a conical region of disturbance which spreads continuously. Such a disturbance is called shock waves.

What is Bow Wave?
When a motor boat travels faster than sound, then waves just like shock waves are produced on the surface of water. These waves are called bow waves.   

Definition of Doppler Effect

If there is a relative motion between source of sound and observer. The apparent frequency of sound heard by the observer is different from the actual frequency of sound emitted by the source. This phenomenon is called Doppler Effect.

Previous year Asked Questions on Sound in Competitive Exams

Which Waves are used in sonography? {SSC, 2014}
Answer: Ultra Sonic waves

Which waves can be polarized? {SSC, 2014}
Answer: Light Waves

X-rays were discovered by
Answer: Roentgen

Doppler Effect is independent of
Answer: Distance between Source and Observer

The Sounds having frequency 20 Hz to 20,000 Hz are called {BPSC, 2015}
Answer: Audible Sounds

SONAR is based on the principle of
Answer: Echo

The Quality of musical note depends upon? {INDA 2001}
Answer: Its Harmonic content

A Noise level of 100 decibel would correspond to
Answer: Noise from machine shop

Instrument used to study the behavior of vibrating string is {SSC 2013}
Answer: Sonometer

Pitch is sensation which depends upon
Answer: Frequency

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