Understanding Sound Energy

Sound Energy

• Sound energy is a form of energy that allows us to hear sounds.
• Sound is produced when an object vibrates, such as a tuning fork, stretched rubber band, vocal cords, strings, or air column.

Propagation of Sound

• Sound requires a medium to propagate, which can be a gas, liquid, or solid.
• Sound waves propagate through compressions and rarefactions of particles in the medium.
• Sound is a mechanical wave that cannot travel through vacuum.
• Sound waves are longitudinal waves, where particles move in a direction parallel to the propagation of the disturbance.

Speed of Sound

• The speed of sound depends on the properties of the medium, including pressure, density, and temperature.
• Speed of sound: Solids > Liquids > Gases.
• Speed of sound in air: 331 m/s at 0°C and 344 m/s at 22°C.
• When a source emits sound with speed greater than the speed of sound in air, it creates a sonic boom.

Reflection of Sound Waves

• Sound waves follow the laws of reflection, bouncing off the surface of solid and liquid.
• The phenomenon where a sound produced is heard again due to reflection is called an echo.
• Minimum distance for obstruction or reflective surface to hear an echo: 17.2 m.
• Multiple echoes can be heard due to multiple reflections.

Reverberation

• The persistence of sound due to multiple reflections is called reverberation.
• Examples: Auditorium and a big hall.
• Excessive reverberation is undesirable, and can be reduced by using sound-absorbing materials.

Uses of Multiple Reflection

• Megaphone, horns, musical instruments (e.g. trumpets)
• Stethoscope
• Concert halls, conference halls, cinema halls

Range of Hearing

• Human ear can hear sound in a frequency range of about 20Hz to 20kHz.
• Sounds of frequencies less than 20Hz are known as infrasonic sound or infrasound.
• Sounds of frequency greater than 20kHz are known as ultrasonic or ultrasound.

Applications of Ultrasound

• Industry: Cleaning instruments and electronic components.
• Medical science: Echocardiography, Ultrasonography, Breaking small stones formed in the kidneys.
• Communication: SONAR (Sound Navigation And Ranging)

SONAR

• Technique that uses sound or ultrasonic waves to measure distance and detect objects on or under the water surface.
• SONAR consists of a transmitter and detector mounted on a boat or ship.
• Distance can be measured using the formula: 2d = v × t.