The Production and Propagation of Sound

• Sound is vibrations moving through a medium, audible when reaching an ear.
• Musical sound has a pleasing effect, while noise is jarring and unpleasant.

Sound Production

• Sound is produced when objects vibrate
• Vibrations cause the particles of the surrounding medium (air, water, solids) to vibrate back and forth, creating sound waves
• The sound waves travel through the medium to the ears, resulting in hearing sound
• all sounds originate from vibration

Human Sound Production

• Humans produce sound through vocal cord vibration in the larynx
• Air from the lungs passing through the vocal cords causes vibration and creates sound
• Pitch changes based on the vocal cords tightness
• The mouth, tongue, and lips then modify this sound to form speech
• Volume hinges upon the force of air expelled from the lungs

Sound Propagation

• Sound needs a medium (air, water, solids) to travel as mechanical waves
• These waves are created by the vibration of particles in the medium
• These particles transfer sound energy from one to another.
• Without a medium, as in a vacuum, sound cannot travel
• Sound travels faster through solids than liquids or gasses

How We Hear

• Sound waves travel through the ear canal to the ear
• Incoming sound waves cause the eardrum to vibrate
• From the eardrum, the vibrations pass to three small bones: the hammer, anvil, and stirrup
• The bones in the middle then amplify the vibrations
• These vibrations are then transmitted to the cochlea in the inner ear
• The cochlea converts the vibrations to electrical signals
• Electrical signals are sent to the brain via the auditory nerve, where they are interpreted as the sound.

Vibration Characteristics

• Amplitude is the maximum extent of vibrations from a mean position
• Time period is the time taken for one complete oscillation of a vibrating particle
• Frequency measures the # of vibrations occurring in one second, measured in Hertz (Hz)
• High frequency results in a high-pitched sound, and low frequency results in a low-pitched sound
• Frequency is inversely proportional to the time period

Audible and Inaudible Sounds

• Inaudible sounds have a frequency above 20,000 Hz or below 20 Hz, which humans cannot hear
• Low-frequency inaudible sounds are called Infrasonics
• High-frequency inaudible sounds are called Ultrasonics
• Audible sounds are vibrations with frequencies between 20 Hz and 20,000 Hz

Noise vs. Music

• Noise is irregular and unpleasant, produced by random vibrations with no harmony or rhythm
• Examples of noise include traffic, loud machines, and construction sounds
• Music is a pleasant, organized, and harmonious sound produced by regular vibrations with rhythm, melody, and harmony

Noise Pollution

• Noise pollution is excessive/harmful levels of unwanted sound
• Noise pollution occurs when sound exceeds acceptable limits and causes negative effects
• Common noise pollution sources include traffic, industry, construction, loudspeakers, and appliances
• Exposure effects on health can be hearing loss, stress, sleep disturbance, high blood pressure, and reduced concentration
• Environmental impacts can disrupt wildlife, affecting animal behavior, communication, and ecosystems
• Prevention can be soundproofing, planting trees, regulating noise levels, and raising awareness

Harms of Noise Pollution

• Noise pollution can cause hearing loss or damage
• Noise pollution can cause increased stress and anxiety
• Noise pollution can cause disturbed sleep patterns, leading to fatigue and lower productivity
• Long-term exposure can contribute to elevated blood pressure and cardiovascular issues
• Noise can hinder focus and concentration
• Noise pollution can disturb animal behaviour, affecting their communication, reproduction, and survival

Measures to Limit Noise Pollution

• Install soundproof materials in buildings
• Restrict loudspeakers and amplifiers in public areas
• Implement stricter noise standards for vehicles
• Plant trees as natural sound barriers
• Separate industrial areas from residential areas
• Raise public awareness and promote noise-reducing behavior

Sound Characteristics

• Loudness distinguishes faint and loud sounds depending on amplitude
• Pitch distinguishes soft/shrill sounds based on vibration frequency
• Quality distinguishes musical sounds from different instruments, even with matching loudness and pitch

Sound is produced by vibrating objects that create sound waves in a medium. Humans produce sound through vocal cord vibration in the larynx, which is modified for speech. Sound propagates as mechanical waves.