Science Chapter on Sound and Oscillation

Sound

• Sound is energy that creates a sensation in the ears
• It helps people communicate, recognize voices, and distinguish musical instruments
• Examples of everyday sounds include barking dogs, vehicle horns, and human voices

Production of Sound

• The core of sound production is vibration
• A body moving back and forth (oscillating) creates sound
• Vibrations travel through the air to reach the ears
• Vibrations can be seen, felt, and heard

Characteristics of Sound

• Pitch: A characteristic used to distinguish between sounds (high or low)
• Loudness: Another characteristic that distinguishes sounds (loud or quiet). This is associated with the amplitude of vibration
• Amplitude: Describes the maximum displacement of a vibrating object
• Frequency: Number of oscillations per second measured in hertz (Hz)
• Time period: Time taken for one complete oscillation

Oscillatory Motion of a Simple Pendulum

• A simple pendulum has a bob attached to a string
• When released from one end, it exhibits oscillatory motion
• The initial position is the mean position where there is no oscillation

All Characteristics of Sound (Explanation)

• Amplitude: Maximum displacement of oscillation.
• Time period: Time for one complete oscillation
• Frequency: Number of oscillations per second (measured in Hertz).

Propagation of Sound

• Sound travels through media like solids, liquids, and gases
• Sound travels as waves, creating compressions (high pressure) and rarefactions (low pressure)
• Sound cannot travel through a vacuum (no medium)

How Humans Hear Sound

• The ear has three parts: Outer, Middle, and Inner Ear
• Outer Ear collects sound waves; Middle Ear transmits vibrations to the Inner Ear; Inner Ear contains hair cells that transmit sound signals to the brain

Speed of Sound

• The speed of sound depends on the medium (solid, liquid, or gas) and the temperature
• Sound travels faster in solids and slower in gases

Reflection of Sound

• Sound reflects off obstacles, creating echoes
• Echoes occur when the sound is reflected back
• Reverberation refers to multiple echoes

Absorption of Sound

• Materials such as curtains absorb sound
• This is used to reduce unwanted sound in rooms like auditoriums

Uses of Echo

• Sonar (Sound Navigation and Ranging) is used to locate underwater objects
• Bats use echolocation to navigate and find food in the dark

Sound Produced by Musical Instrumentals

• String instruments: Sound produced by vibrations of strings
• Wind instruments: Sound produced by vibrations of air columns
• Percussion instruments: Sound produced by vibrations of membranes or other surfaces

Audible and Inaudible Sounds

• Audible sounds are within the range of human hearing (20 Hz - 20,000 Hz)
• Sounds outside this range are inaudible. These include Infrasonic sounds and ultrasonic sounds

Music and Noise

• Pleasant sounds (music) have regular vibrations
• Unpleasant sounds (noise) have irregular vibrations
• Loudness is measured in decibels
• Levels above 80 decibels can be damaging to hearing