# Sound Study Notes for MPSC State Exam 2021

By BYJU'S Exam Prep

Updated on: September 25th, 2023

Sound Study Notes for MPSC State Exam 2021: Physics is an important subject for all MPSC exams. The MPSC State Service Examination has about six to seven questions on this subject, as well as the MPSC Combined Exam has three to four questions on this component, all the examinations like Police Recruitment, Health Department have questions on Physics. So it is important to study this topic.

Table of content

## Sound

• A sound is a form of energy that is emitted by a vibrating body that travels in the form of waves and causes the sensation of hearing.
• The sound is produced by vibrations.
• Sound is transmitted in the form of waves.
• Sound waves are Mechanical – Longitudinal waves.

## Sound characteristics

• When sound waves travel through – the density of the medium changes.
• Compression
• The part that carries the vibrations is the part with the crowded mass of particles.
• Compression has a high density as well as energy.
• Rarefaction
• The part of the vibration where the particles are scattered far away.
• Rarefaction has less density and less energy.

### Wavelength

• The distance between the two nearest particles that are in the same phase is called wavelength.
• SI:m

### Amplitude

• The maximum displacement of the particles of a medium from their mean positions during the propagation of a wave is called the amplitude of the wave.
• If amplitude increases, wavelength increases.
• As the wavelength increases, the sound becomes loud.
• SI:m

### Frequency

• Frequency is the number of waves that occur over a period of time.
• SI: Hertz (Hz).

### Time period

• The time required to produce one complete wave (or cycle) is called the time period of the wave.

### Pitch of Sound

• Pitch depends on its frequency. The higher the frequency of the sound, the higher Pitch of Sound.
• The higher pitch, the sharper the sound.
• The pitch is higher for women than men.

### Velocity of Sound

• The speed of sound is lowest in air, medium in liquid and highest in static.
• Sound cannot travel through a vacuum.

## Types of sounds

### Audible range (Sonic)

• The frequency at which a human can hear this sound is 20Hz – 20KHz.
• g. human voice.

### Ultrasonic

• Its frequency is more than 20KHz.
• Humans cannot hear the ultrasonic sound, but cats, chimpanzees, rats, whereabouts, toddlers, dolphins, bats (produces up to 1 lakh Hz), etc.
• Usage:
• To detect tumours in the body
• To monitor fetal growth
• In the ECG Machine
• To preserve milk-substances

### Infrasonic Sound

• Its frequency is less than 20Hz.
• Elephants, Rhinos, Whales, etc. produce Infrasonic Sound.
• This type of sound is first produced during an earthquake, so it is used in disaster management.

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