1. © 2010 Pearson Education, Inc. Conceptual Physics 11 th Edition Chapter 21: MUSICAL SOUNDS

2. © 2010 Pearson Education, Inc. Ch 21 Objective: This lecture will help you understand: Noise and Music Musical Sounds Sound Intensity and Loudness Quality Musical Instruments Fourier Analysis Digital Versatile Discs (DVDs) Warm- Up Quiz

3. © 2010 Pearson Education, Inc. Musical Tone Three characteristics: –Pitch- each note has its own pitch determined by frequency of sound waves as received by the ear…rapid vibrations = high pitch and slow vibrations = low pitch determined by fundamental frequency, lowest frequency –Intensity determines the perceived loudness of sound –Quality determined by prominence of the harmonics (multiples of the fundamental and are known as 1 st, 2 nd …..harmonics) determined by presence and relative intensity of the various partials

4. © 2010 Pearson Education, Inc. Pitch Musicians give different pitches different letter names: A, B, C, D, E, F, G. –Notes A through G are all notes within one octave. –Multiply the frequency on any note by 2, and you have the same note at a higher pitch in the next octave. –A piano keyboard covers a little more than seven octaves.

5. © 2010 Pearson Education, Inc. Pitch 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.

6. © 2010 Pearson Education, Inc. Intensity Piano wire vibrates and transfers energy to the piano’s sound board which transfers energy into the air as sound. –The rate at which this occurs is called intensity –EX: What is the intensity of the soundwaves produced by a trumpet at a distance of 3.2m when the power output of the trumpet is 0.20W?

7. © 2010 Pearson Education, Inc. Intensity/Frequency graph Decibel (dB)= intensity of soundwave/intensity of threshold of hearing Loud and soft No units

8. © 2010 Pearson Education, Inc. Quality Most musical sounds are composed of a superposition of many tones differing in frequency. The various tones are called partial tones, or simply partials. The lowest frequency, called the fundamental frequency, determines the pitch of the note. A partial tone whose frequency is a whole-number multiple of the fundamental frequency is called a harmonic. A composite vibration of the fundamental mode and the third harmonic is shown in the figure.

9. © 2010 Pearson Education, Inc. Exit Ticket HW: Pg 378 2, 7, 9, 24, 31, Pg 379 42, and 4

10. © 2010 Pearson Education, Inc. Ch 21 Objective: This lecture will help you understand: Noise and Music Musical Sounds Sound Intensity and Loudness Quality Musical Instruments Fourier Analysis Digital Versatile Discs (DVDs) Warm- Up Review HW

11. © 2010 Pearson Education, Inc. Phonograph There are grooves in a phonograph that move the stylus These mechanical vibrations are transformed into electrical vibrations and produce sound https://www.youtube.com/watch?v=EOiF t47CsXo

12. © 2010 Pearson Education, Inc. Digital Versatile Discs (DVDs) The output of phonograph records was signals like those shown below. This type of continuous waveform is called an analog signal. The analog signal can be changed to a digital signal by measuring the numerical value of its amplitude during each split second.

13. © 2010 Pearson Education, Inc. Digital Versatile Discs (DVDs) Microscopic pits about one-thirtieth the diameter of a strand of human hair are imbedded in the CD or DVD –The short pits corresponding to 0. –The long pits corresponding to 1. When the beam falls on a short pit, it is reflected directly into the player’s optical system and registers a 0. When the beam is incident upon a passing longer pit, the optical sensor registers a 1. Hence the beam reads the 1 and 0 digits of the binary code.

14. © 2010 Pearson Education, Inc. A DVD has more storage than a CD because it has smaller pits Blue-ray uses blue wavelength So the shorter wavelength means even MORE pits = high def.