Unit 1. Sound
1. Sound
2. Difference between sound and noise
3. Silence
4. Qualities of sound
5. Learn more: Resonance experiment
1. Sound
Sound is produced when an object vibrates. That movement is transmitted in the form of sound waves and it reaches our ears. Sound travels through the air at 349 meters per second (m/s). It travels faster through water and solid objects like wood or iron.
The science of hearing - Douglas L. Oliver
Hearing is the process in which sound waves enter the ear and make the eardrum vibrate. This movement is transformed into nerve impulses and transmitted to the brain, which interprets them as sounds.
Ear parts
Click!
2. Difference between sound and noise
The difference between sound and noise is the sort of waves: sound waves are regular and noise waves are irregular. Noise is usually associated with an annoying feeling, while sound can be related to a pleasant feeling.
3. Silence
Silence is the absence of sound or noise. It is as important as sound, because both elements give structure to the musical discourse. Silence is necessary as the previous condition to enjoy music and it can be used as a break between phrases or sections, as a contrast with sounds or as a resource of great expressive force.
Absolute silence does not exist. Even if we could isolate ourselves completely from other sounds, we would still hear our own body’s inner sounds.
Anechoic chamber
4. Qualities of sound
Every sound has four qualities: pitch, duration, intensity and timbre.
Qualities of sound
5. Learn more: Resonance experiment
Certain frequencies vibrate the metal plate in such a way that it creates areas where there is no vibration. The sand "falls" into those areas, creating beautiful geometric patterns. As the frequency increases in pitch the patterns become more complex.
Equipment: a tone generator, a wave driver (speaker) and a metal plate attached to the speaker. They also added sand to the plate.
Chladni plate experiment