1. By Prof. Lydia Ayers

2. Acoustics: The Properties of Sound air pressure changes when objects vibrate, producing sound in the earair pressure changes when objects vibrate, producing sound in the ear pound a tablepound a table pluck a stringpluck a string

3. Sound Waves vibrations are transmitted to our ears by a medium — usually airvibrations are transmitted to our ears by a medium — usually air sound waves radiate through air outward from the source sound like waves in water that radiate in circles from a tossed pebblesound waves radiate through air outward from the source sound like waves in water that radiate in circles from a tossed pebble

4. Sound Waves sound waves also radiate through water and solid materials, such as doorssound waves also radiate through water and solid materials, such as doors listen to underwater sounds in the swimming pool!listen to underwater sounds in the swimming pool! get a friend to hum underwaterget a friend to hum underwater how far away can you hear the sound?how far away can you hear the sound?

5. Sound Waves alternately crowding and spreading apart of air moleculesalternately crowding and spreading apart of air molecules compressing = crowdingcompressing = crowding rarefying = spreading apartrarefying = spreading apart animation by Edward Wong

6. Vibrating String

7. String Vibrations rubber band experimentrubber band experiment hold both ends of a rubber bandhold both ends of a rubber band have a partner pluck the rubber bandhave a partner pluck the rubber band notice the movement of the rubber bandnotice the movement of the rubber band the whole length is vibrating

8. String Vibrations strings and pipes vibrate in segments of their length, as well as in their entirety — at the same timestrings and pipes vibrate in segments of their length, as well as in their entirety — at the same time fundamentalfundamental sound produced by vibration of total lengthsound produced by vibration of total length usually loudest sound producedusually loudest sound produced

9. HarmonicsHarmonics The sounds produced by the segments of the string lengthsThe sounds produced by the segments of the string lengths [i:18] harmonics demo on sanxian[i:18] harmonics demo on sanxian Full string length= 1 st harmonicFull string length= 1 st harmonic ½ string length= 2 nd harmonic ½ string length= 2 nd harmonic

10. HarmonicsHarmonics pipes like the flute also have harmonics — live demo pipes like the flute also have harmonics — live demo

11. How Does Sound Work? Many musical sounds are made of special combinations of harmonicsMany musical sounds are made of special combinations of harmonics

12. How Loud Are the Harmonics? Here is a graph of the first 15 harmonics of a [i:19] bassoon toneHere is a graph of the first 15 harmonics of a [i:19] bassoon tone

13. Here is the average loudness of the same [i:19] bassoon toneHere is the average loudness of the same [i:19] bassoon tone How Loud Are the Harmonics?

14. The bassoon tone's first harmonic fades in and out like this:The bassoon tone's first harmonic fades in and out like this: How Loud Are the Harmonics?

15. Harmonic Series Using its harmonic pattern, we can recreate a bassoon toneUsing its harmonic pattern, we can recreate a bassoon tone

16. SourcesSources BooksBooks Turek, The Elements of MusicTurek, The Elements of Music Charles Dodge, Computer MusicCharles Dodge, Computer Music