Chapter 21 Musical Sounds

Three characteristics of a musical tone: 1. NOISE VERSUS MUSIC Wham - Noise and Wave Forms Three characteristics of a musical tone: Pitch Loudness Quality

2. 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. Response to high pitch usually declines with age.

3. SOUND INTENSITY AND LOUDNESS refers to pressure variations Intensity is directly proportional to the pressure amplitude squared. 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.

Loudness b = 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 different frequencies.

Common Sound Intensities

Response of the Ear at Constant Loudness

4. 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 Instrument

Human Voice

Harmonics 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 Harmonics 1st 2nd Sum

Demo - Harmonics on a Guitar Demo - Organ Pipe

Speaker Shortcomings The brain can fill in missing lower harmonics that small speakers cannot create.

5. MUSICAL INSTRUMENTS Three basic types stringed, air column, and percussion Because of energy loss, string sections in orchestras are generally larger. Electronic

6. 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 Harmonics Spreadsheet

7. COMPACT DISCS Phonograph players give analog signals. Digital signal is in binary code. CD has flats and pits and is sampled 44,100 times per second.

Diatonic C Major Scale Letter Frequency Frequency Note Name (Hz) ratio Interval do C 264 9/8 Whole re D 297 10/9 Whole mi E 330 16/15 Half fa F 352 9/8 Whole sol G 396 10/9 Whole la A 440 ti B 495 do C 528

Chapter 21 Review Questions

The quality of a musical note can be changed by simply playing the note on a different instrument. (a) True (a) True (b) False

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. (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. (a) True (a) True (b) False

The ear can “Fourier analyze” a sound wave, but the eye cannot “Fourier analyze” a light wave. (a) True (a) True (b) False

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