Chapter 24 –SoundChapter 24 –Sound

24.3 –Sound , Perception and 24.3 –Sound , Perception and MusicMusic

pp. 590-597pp. 590-597

24.3 Sound perception and 24.3 Sound perception and musicmusic

• When you hear a When you hear a sound, the nerves in sound, the nerves in your ear your ear respond to respond to more than 15,000 more than 15,000 different frequencies different frequencies at onceat once..

• The brain makes The brain makes sense of complex sense of complex sound because the sound because the ear ear separates the separates the sound into different sound into different frequenciesfrequencies..

24.3 Sound perception and 24.3 Sound perception and musicmusic

• A A frequency spectrumfrequency spectrum shows the shows the amplitudes of different frequencies amplitudes of different frequencies present in a sound.present in a sound.

24.3 Sonograms24.3 Sonograms• More information is More information is

found in a found in a sonogramsonogram which which combines three combines three sound variables: sound variables:

1.1. frequency,frequency,

2.2. time, and time, and

3.3. amplitude amplitude (loudness).(loudness).

24.3 Sonograms24.3 Sonograms

Which letter represents a soft sound lasting 5 seconds?What is it’s frequency?

24.3 How we hear sound24.3 How we hear sound• The parts of the ear work together:The parts of the ear work together:

1. When the eardrum vibrates, three small bones transmit the vibrations to the cochlea.

2. The vibrations make waves inside the cochlea, which vibrates nerves in the spiral.

3. Each part of the spiral is sensitive to a different frequency.

24.3 Sound protection24.3 Sound protection

• Listening to loud sounds Listening to loud sounds for a long time causes for a long time causes the hairs on the nerves the hairs on the nerves in the cochlea to in the cochlea to weaken weaken or break off resulting in or break off resulting in permanentpermanent damage damage..

NOISE POLLUTIONNOISE POLLUTION

• When noise reaches a level that When noise reaches a level that causes pain or damages the body it causes pain or damages the body it is called is called noise pollution.

• Noise pollution can damage Noise pollution can damage the inner ear, causing permanent hearing loss..

• Noise pollution can contribute to Noise pollution can contribute to sleeplessness, high blood pressure and stress.

WHITE NOISEWHITE NOISE

•This is an equal mixture of all frequencies (like white light is a (like white light is a mixture of all colors).mixture of all colors).

• White noise machines are used White noise machines are used to calm people and help make them sleep..

24.3 Music24.3 Music

• The The pitchpitch of a sound is how high or of a sound is how high or low we hear its frequency.low we hear its frequency.

• RhythmRhythm is a regular time pattern in a is a regular time pattern in a series of sounds.series of sounds.

• MusicMusic is a combination of sound and is a combination of sound and rhythm that we find pleasant.rhythm that we find pleasant.

24.3 The musical scale24.3 The musical scale• Most of the music you listen to is Most of the music you listen to is

created from a pattern of frequencies created from a pattern of frequencies called a called a musical scalemusical scale..

24.3 Music and notes24.3 Music and notes• Each frequency in the scale is called a Each frequency in the scale is called a note.note. • The C major musical scale that starts on the The C major musical scale that starts on the

note C (262 Hz).note C (262 Hz).

24.3 Music and harmony24.3 Music and harmony

• HarmonyHarmony is the study of how sounds work is the study of how sounds work together to create effects desired by the together to create effects desired by the composer.composer.

• The tense, dramatic sound track of a horror The tense, dramatic sound track of a horror movie is a vital part of the audience’s movie is a vital part of the audience’s experience. experience.

• Harmony is based on Harmony is based on the frequency the frequency relationships of the musical scale.relationships of the musical scale.

24.3 Superposition24.3 Superposition• The The superposition principle superposition principle states that states that

when sound waves occur at the same time when sound waves occur at the same time they combine to make a complex wave. they combine to make a complex wave.

• When two frequencies of sound are not When two frequencies of sound are not exactly equal in value, the loudness of the exactly equal in value, the loudness of the total sound seems to oscillate or total sound seems to oscillate or beat.beat.

24.3 Music and harmony24.3 Music and harmony

• When we hear more than one When we hear more than one frequency of sound and the frequency of sound and the combination sounds pleasant, we call combination sounds pleasant, we call it it consonanceconsonance..

• When the combination sounds When the combination sounds unsettling, we call it unsettling, we call it dissonance.dissonance.

24.3 Making sounds24.3 Making sounds• The human voice is complex The human voice is complex

sound that starts in the sound that starts in the larynx, at the top of your larynx, at the top of your windpipe.windpipe.

• The sound is changed by The sound is changed by passing over by expandable passing over by expandable folds (vocal cords) and folds (vocal cords) and through openings in the through openings in the throat and mouth.throat and mouth.

3 MAIN FAMILIES OF 3 MAIN FAMILIES OF INSTRUMENTSINSTRUMENTS

•String instrumentsString instruments

•Wind instrumentsWind instruments

•Percussion instrumentsPercussion instruments

24.3 Making sounds24.3 Making sounds• For a guitar in standard For a guitar in standard

tuning, the heaviest string tuning, the heaviest string has a natural frequency of has a natural frequency of 82 Hz 82 Hz and the lightest a and the lightest a frequency of frequency of 330 Hz330 Hz..

• Tightening a string raises Tightening a string raises its natural frequency and its natural frequency and loosening lowers it.loosening lowers it.

WIND INSTRUMENTSWIND INSTRUMENTS

•2 types of wind instruments:2 types of wind instruments:

– WoodwindWoodwind

– BrassBrass

WIND INSTRUMENTSWIND INSTRUMENTS

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

PERCUSSIONPERCUSSION

•How they make sounds: How they make sounds: They produce sound when they are struck

24.3 Harmonics and music24.3 Harmonics and music• The same note sounds different when The same note sounds different when

played on different instruments.played on different instruments.• Suppose you compare the note C (262 Hz) Suppose you compare the note C (262 Hz)

played on a guitar and the same note played on a guitar and the same note played on a piano.played on a piano.

• The variation comes from the The variation comes from the harmonicsharmonics in complex sound.in complex sound.

• A single C note from a grand piano might A single C note from a grand piano might include 20 or more different harmonics.include 20 or more different harmonics.

24.3 Harmonics and music24.3 Harmonics and music

• A tuning fork is a A tuning fork is a useful tool for tuning useful tool for tuning an instrument an instrument because it produces because it produces a a singlesingle frequency frequency