1. What Is Amplitude?
Amplitude is the maximum displacement of a vibrating particle from its rest position.
It tells us how strong the vibration is. Larger amplitude means the particle moves farther from its central position during vibration.
2. What Is Loudness?
Loudness is the sensation that tells us whether a sound is strong or weak.
Loudness depends mainly on amplitude. A sound with a large amplitude is loud, and a sound with a small amplitude is soft.
2.1. Perception of Loudness
The ear senses the energy carried by the sound wave. More energy means greater loudness. Higher amplitude delivers more energy to the ear.
3. Relation Between Loudness and Amplitude
Loudness increases when amplitude increases and decreases when amplitude decreases.
In simple terms:
- Higher amplitude → louder sound
- Lower amplitude → softer sound
3.1. Wave Representation
In a wave diagram, loud sounds have tall wave peaks and deep troughs, while soft sounds have shorter peaks and shallower troughs.
4. Energy and Amplitude
A sound wave with larger amplitude carries more energy. The energy transferred to the air particles is greater, causing them to vibrate more strongly.
4.1. Everyday Observation
When you strike a drum gently, it produces small-amplitude vibrations and a soft sound. Striking harder creates larger-amplitude vibrations and a louder sound.
5. Examples of Loudness and Amplitude
- Turning up the volume on a speaker increases amplitude and makes the sound louder.
- A whisper has very small amplitude, so it feels soft.
- A shout has large amplitude, so it feels loud.
- Gently plucking a string produces soft sound; plucking it forcefully produces loud sound.
6. Factors Affecting Loudness (Other Than Amplitude)
Although amplitude is the main factor, a few other things also affect how loud a sound feels.
6.1. Distance
Loudness decreases as distance from the source increases because the energy spreads out while travelling.
6.2. Sensitivity of the Ear
Some people may perceive the same sound as louder or softer depending on how sensitive their ears are.
6.3. Obstructions
Walls, furniture, and other objects can absorb or block some of the sound energy, reducing loudness.