1. Musical Sounds
Chapter 21

2. The difference between noise & music…
Noise corresponds to an irregular vibration of the eardrum produced by some irregular vibration in our surroundings.
The sound of music has a different character, having periodic tones – or musical “notes”
But as we know the line that separates these two is thin and often subjective

3. Noise

4. Music

5. Pitch

6. The pitch of a sound relates to frequency.
The pitch corresponds to the lowest frequency component.
Rapid vibrations (high frequency) produce a high note and slow vibrations (low frequency) produce a low notes

7. Different musical notes are obtained by changing the frequency of the vibrating sound source.
This is usually done by altering the size, the tightness, or the mass of the vibrating object.

8. The human ear can hear sounds with frequencies up to 18,000 Hz.
High pitched sounds used in music are often less than 4,000 Hz.
In general, the upper limit of hearing in people gets lower as they get older.

9. Sound Intensity & Loudness

10. The intensity of sound depends on the amplitude of pressure variations with in the sound wave.
Intensity is measured in units of watts/square meter
The human ear responds to intensities covering the enormous range from 10^-12 to more than 1 watts/square meter
Because the range is so great, intensities are scaled by factors of 10

11. Physiological hearing damage begins at exposure to 85 decibels, the degree of damage depending on the length of exposure and on frequency characteristics.

12. Damage from loud sounds can be temporary or permanent, depending on whether the organ of Corti, the receptor organ in the inner ear, is impaired or destroyed.
A single burst of sound can produce vibrations in the organ intense enough to tear it apart.
Less intense, but severe, noise can interfere with cellular processes in the organ and cause its eventual breakdown

14. Sound intensity is purely objective and physical attribute of a sound wave, it can be measured by various acoustical instruments
Like the oscilloscope

15. Loudness, is a physiological sensation.
The ear senses some frequencies much better than others
The loudest sounds we can tolerate have intensities a trillion times greater than the faintest sounds

16. Quality

17. Quality
The characteristic timbre of a musical sound which is governed by the number and relative intensities of partial tines

18. Partial Tone Single-frequency component sound wave of a complex time.
When the frequency of a partial tone is an integer multiple of the lowest frequency, it is referred to as a harmonic.

19. Fundamental Frequency
The lowest frequency of vibration, or first harmonic, in a musical tone.

20. Fourier Analysis

21. In 1822, the French mathematician Joseph Fourier discovered a mathematical regularity to the component parts of periodic wave motion.
He found that even the most complex periodic wave motion can be disassembled into simple sine waves that add together.

22. A sine wave is the simplest of waves, having a single frequency.
Fourier found that all periodic waves may be broken down into constituent sine waves of different amplitudes and frequencies.
The mathematical operation for doing this is known as the Fourier analysis.

23. Our ear performs a sort of Fourier analysis automatically.
It sorts out the complex jumble of air pulsations that reach it and transforms them into pure tones when we listen.
What combinations of tones we have learned to focus our attention on determines what we hear when we listen to a concert. We can direct our attention to specific sounds and instruments, isolating them.