24.3 –Sound , Perception and Music pp. 590-597 Chapter 24 –Sound 24.3 –Sound , Perception and Music pp. 590-597

24.3 How we hear sound The parts of the ear work together: When the eardrum vibrates, three small bones transmit the vibrations to the cochlea. The vibrations make waves inside the cochlea, which vibrates nerves in the spiral. Each part of the spiral is sensitive to a different frequency.

24.3 Sound protection Listening to loud sounds for a long time causes the hairs on the nerves in the cochlea to weaken or break off resulting in permanent damage.

NOISE POLLUTION When noise reaches a level that causes pain or damages the body it is called noise pollution. Noise pollution can damage the inner ear, causing permanent hearing loss. Noise pollution can contribute to sleeplessness, high blood pressure and stress.

WHITE NOISE This is an equal mixture of all frequencies (like white light is a mixture of all colors). White noise machines are used to calm people and help make them sleep.

24.3 Music The pitch of a sound is how high or low we hear its frequency. Rhythm is a regular time pattern in a series of sounds. Music is a combination of sound and rhythm that we find pleasant.

24.3 Music and harmony Harmony is the study of how sounds work together to create effects desired by the composer. Harmony is based on the frequency relationships of the musical scale.

24.3 Music and harmony When we hear more than one frequency of sound and the combination sounds pleasant, we call it consonance. When the combination sounds unsettling, we call it dissonance.

24.3 Making sounds For a guitar in standard tuning, the heaviest string has a natural frequency of 82 Hz and the lightest a frequency of 330 Hz. Tightening a string raises its natural frequency and loosening lowers it.

WIND INSTRUMENTS How wind instruments produce sound: a vibration is created at one end of its air column, and then the vibration creates standing waves in the air column.

24.3 Harmonics and music The same note sounds different when played on different instruments. Suppose you compare the note C (262 Hz) played on a guitar and the same note played on a piano. The variation comes from the harmonics in complex sound. A single C note from a grand piano might include 20 or more different harmonics.