Chapter 21Chapter 21

Musical SoundsMusical Sounds

1. NOISE VERSUS MUSIC1. NOISE VERSUS MUSIC

Wham - Noise and Wave FormsWham - Noise and Wave Forms

PitchPitch

LoudnessLoudness

QualityQuality

Three characteristics of a musical tone:Three characteristics of a musical tone:

2. PITCH2. PITCH

The pitch of a sound relates 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.

Change pitch by altering the vibrating source.Change pitch by altering the vibrating source.

Response to high pitch usually declines

with age.

3. SOUND INTENSITY AND LOUDNESS3. 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.

2AI

LoudnessLoudness

= 10 log(I/Io)

Measured in decibels (db)A difference of 10 dB corresponds to a ratio of

intensities of 10X.

Loudness depends on our sensitivity to Loudness depends on our sensitivity to different frequencies.different frequencies.

Common Sound IntensitiesCommon Sound Intensities

Source of Sound Intensity (W/m2) Sound Level (db)

Jet 30 m away 102 140

Air-raid siren, nearby 1 120

Disco music, amplified 10-1 110

Riveter 10-3 90

Busy street traffic 10-5 70

Conversation in home 10-6 60

Quiet radio in home 10-8 40

Whisper 10-10 20

Rustle of leaves 10-11 10

Threshold of hearing 10-12 0

Response of the Ear atConstant Loudness

Response of the Ear atConstant Loudness

4. QUALITY4. QUALITY

Quality is the same thing as timbre.

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.

Same Note - Different InstrumentSame Note - Different Instrument

Human VoiceHuman Voice

Harmonics and OvertonesHarmonics and Overtones

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.

Adding HarmonicsAdding Harmonics

1st

2nd

Sum

Demo - Harmonics on a GuitarDemo - Harmonics on a Guitar

Demo - Organ PipeDemo - Organ Pipe

Speaker ShortcomingsSpeaker Shortcomings

The brain can fill in missing lower

harmonics that small speakers cannot

create.

5. MUSICAL INSTRUMENTS5. MUSICAL INSTRUMENTS

Three basic types stringed, air column, and percussion

Because of energy loss, string sections in orchestras are generally larger.

Electronic

6. FOURIER ANALYSIS6. 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.

Adding HarmonicsAdding Harmonics

Spreadsheet

7. COMPACT DISCS7. COMPACT DISCS

Phonograph players give analog signals.Phonograph players give analog signals.

Digital signal is in binary code.Digital signal is in binary code.

CD has flats and pits and is sampled 44,100 times CD has flats and pits and is sampled 44,100 times

per second.per second.

Diatonic C Major ScaleDiatonic C Major Scale

Letter Frequency FrequencyLetter Frequency FrequencyNote Name (Hz) ratio Interval

do C 264 9/8 Wholere D 297 10/9 Wholemi E 330 16/15 Halffa F 352 9/8 Wholesol G 396 10/9 Wholela A 440 9/8 Wholeti B 495 16/15 Halfdo C 528

Chapter 21 Review QuestionsChapter 21 Review Questions

The quality of a musical note can be changed by simply playing the note on a different instrument.

The quality of a musical note can be changed by simply playing the note on a different instrument.

(a) True

(b) False

(a) True

If the note middle C has a pitch of 262 vibrations per second, its second overtone on a vibrating string has a frequency of

If the note middle C has a pitch of 262 vibrations per second, its second overtone on a vibrating string has a frequency of

(a) 131 vibrations per second(b) 262 vibrations per second(c) 524 vibrations per second(d) 786 vibrations per second(e) none of the above(d) 786 vibrations per second

The three characteristics of a musical tone are

loudness, quality, and timbre. The three characteristics of a musical tone are

loudness, quality, and timbre.

(a) True

(b) False(b) False

The wavelength of the fundamental vibration on a l m long string is half as long as the wavelength of the fundamental vibration in a closed organ pipe of l m length.

The wavelength of the fundamental vibration on a l m long string is half as long as the wavelength of the fundamental vibration in a closed organ pipe of l m length.

(a) True

(b) False

(a) True

The ear can “Fourier analyze” a sound wave, but the eye cannot “Fourier analyze” a light wave.

The ear can “Fourier analyze” a sound wave, but the eye cannot “Fourier analyze” a light wave.

(a) True

(b) False

(a) True

If the fundamental frequency of a violin string is 440 Hz, what is the frequency in Hz of the first overtone?

If the fundamental frequency of a violin string is 440 Hz, what is the frequency in Hz of the first overtone?

(a) 1320

(b) 880

(c) 440

(b) 880