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Chapter 21Chapter 21Chapter 21Chapter 21
Musical SoundsMusical Sounds
Noise Versus MusicNoise Versus Music
PitchPitch
LoudnessLoudness
Quality Quality
The pitch of a sound is related to its
frequency.
The exact relationship is complex.
For simple sounds, the greater the frequency
the greater the pitch.
For complex sounds, pitch assignment is
an involved psychological process.
1. PITCH1. PITCH1. PITCH1. PITCH
Response to high pitch usually declines
with age.
Change pitch by altering the vibrating source.
2. SOUND INTENSITY AND LOUDNESS2. SOUND INTENSITY AND LOUDNESS
Intensity -refers to pressure variations
The human ear can hear intensities over a tremendously large range.
Loudness depends on intensity in a complicated way. It does not increase as rapidly as intensity.
Intensity is directly proportional to the pressure amplitude squared.
2I A
LoudnessLoudness
= 10 log(I/Io)
Measured in decibels (db)
Loudness depends on our sensitivity to different frequencies.
Demo – Sound MeterDemo – Sound Meter
Common Sound IntensitiesCommon Sound Intensities
Source of SoundSource of Sound Intensity, I (W/mIntensity, I (W/m22))Sound Level, Sound Level, (db) (db)
Threshold of Hearing I0 = 10-12 0
10
20
40
60
70
90
110
120
140
10-11
10-10
10-8
10-6
10-5
10-3
10-1
1
102
Rustle of Leaves
Whisper
Quiet Radio in Home
Conversation in Home
Busy Street Traffic
Riveter
Disco Music Amplified
Air-raid Siren, Nearby
Jet, 30 m Away
3. QUALITY3. QUALITY3. QUALITY3. QUALITY
Quality is the same thing as timbre.
pronounced TAM-burr (French)
It is easy to distinguish two different instruments playing the same note.
The quality of a musical sound depends on the number of partial tones and their relative intensities.
The lowest frequency associated with a musical note is called the fundamental frequency.
Any partial that is a whole number multiple of the fundamental frequency is called a harmonic.
Overtones are consecutively numbered partials of frequency higher than the fundamental.
Harmonics Harmonics
Next SlideNext Slide
First Overtone orThird Harmonic
Fundamental orFirst Harmonic
Second Overtone orFifth Harmonic
Fundamental orFirst Harmonic
First Overtone or
Second Harmonic
Second Overtone orThird Harmonic
Fundamental orFirst Harmonic
First Overtone orSecond Harmonic
Second Overtone orThird Harmonic
Closed Organ Pipe
Open Organ Pipe
URL - Animated Vibrating StringURL - Animated Vibrating String
Demo - Harmonics on a GuitarDemo - Harmonics on a Guitar
Demo - Organ PipeDemo - Organ Pipe
URL - Animated Organ PipeURL - Animated Organ Pipe
Demo - Downing’s Resonance BottleDemo - Downing’s Resonance Bottle
Demo - Speak with different gas in airwayDemo - Speak with different gas in airway
Demo - Soda Straw Reed Demo - Soda Straw Reed
and Train Whistleand Train Whistle
The brain can fill in missing lower
harmonics that small speakers cannot
create.
4. MUSICAL INSTRUMENTS4. MUSICAL INSTRUMENTS4. MUSICAL INSTRUMENTS4. MUSICAL INSTRUMENTS
3 basic typesstringed, air column, and percussion
Because of energy loss, string sections in orchestras are generally larger.
Electronic
5. FOURIER ANALYSIS5. FOURIER ANALYSIS5. FOURIER ANALYSIS5. FOURIER ANALYSIS
The eardrum responds to a sum of all the waves arriving at a particular instant. Yet the individual sounds are “heard.”
Any waveform is composed of an infinite number of simple sine waves of various frequencies and amplitudes.
Slide - Fourier Analysis - URLSlide - Fourier Analysis - URL
Slide - Oboe and ClarinetSlide - Oboe and Clarinet
Slide - Composite WaveSlide - Composite Wave
URL – Simultaneous Multiple URL – Simultaneous Multiple
Harmonics Harmonics
6. COMPACT DISCS6. COMPACT DISCS
Phonograph players give analog signals.Phonograph players give analog signals.
Slide - Analog to DigitalSlide - Analog to Digital
Digital signal is in binary code.Digital signal is in binary code.
CD has flats and pits and is sampled CD has flats and pits and is sampled
44,100 times per second.44,100 times per second.
Slide - Laser DiskSlide - Laser Disk
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