Understanding Sound and Light: Properties and Effects
Sound: Properties and Characteristics
Sound requires a source (an object that vibrates), a medium for transmission (solid, liquid, or gas), and a receiver. A sound is produced when a body vibrates rapidly. Frequency is the number of complete vibrations or oscillations made in one second. Audible sounds occur when a body vibrates with a frequency between 20 Hz and 20,000 Hz. Sound is transmitted through material means—solid, liquid, or gas—but never through a vacuum.
When an object oscillates to one side, it pushes the air particles in its path, causing compression. In the area next to the object, air pressure increases. However, when the object moves to the other side, it creates a low-pressure area behind it, where the particles are farther apart, resulting in expansion or rarefaction.
When these pressure variations reach our ears, the eardrum vibrates. These vibrations are transmitted through the ossicular chain to the cochlea, where they are converted into nerve impulses. The auditory nerve then sends these impulses to the brain, where they are interpreted as sound. Sound travels through the air in the form of waves.
Qualities of Sound
- Loudness: Related to the intensity of sound.
- Pitch: Related to the frequency.
- Timbre: Includes the graphic form of the sound waves.
Sounds can be classified as weak or strong based on their loudness. For example, the sound of a falling leaf is weak, while the sound of a jackhammer is strong. Loudness is related to the intensity of sound, or the amount of energy that reaches our ears. The intensity level of sound is measured using a decibel scale, with the unit of measurement being the decibel.
The pitch of a sound distinguishes between bass and treble. Bass tones correspond to low frequencies, and treble tones correspond to high frequencies.
Timbre is the quality that distinguishes two sounds of equal intensity and frequency emitted by different instruments. It relates to the waveform reflected in its graph. For instance, timbre allows us to differentiate between various musical instruments even when they play the same note.
An echo occurs when sound is reflected on a surface that is at least 17 meters from the source.
Noise Pollution
Noise pollution is a form of pollution associated with urban life. Prolonged exposure to levels above 65 dB can cause irritability, fatigue, and stress, potentially leading to psychological disorders.
Passive Measures
Passive measures attempt to mitigate the impact of noise but do not eliminate the sound emission points. Examples include acoustic templates, green screens or barriers (areas of dense woodland), and protective measures like anti-noise helmets.
Active Measures
Active measures aim to eradicate the sources of noise pollution. Examples include research to improve engine filters, silencers, or machines; measures to prohibit or limit traffic in certain areas; and campaigns to promote public transport use.
Key Concepts
- Audible Range: Occurs when a body vibrates with a frequency between 20 Hz and 20,000 Hz.
- A wave is a disturbance of the medium that propagates through space.
- In a wave, energy, not matter, propagates.
- Sound waves consist of a succession of pressure increases and decreases (compressions and rarefactions).
- Sound needs a medium (solid, liquid, or gas) to propagate.
- Sound travels through air at a speed of 340 m/s at normal temperature (approximately 20°C). The speed is higher in most solids and liquids.
- The reflection of sound produces the phenomena of echo and reverberation.
Light
Radiation is the process by which bodies emit energy that can spread through a vacuum. Light from the sun or stars reaches us after traveling through the void. Light also carries energy that can be converted into electricity. Therefore, we can say that light is a type of radiation.
Light is electromagnetic radiation. Electromagnetic waves are characterized by their propagation speed and frequency.