PHYS 1750: SELECTED TOPICS in PHYSICS
LECTURE 28. Sound Bytes
| 16.1. | What is Sound? | ||
| 1. | Longitudinal: carrier motion parallel to wave motion | ||
| a. | Restoring force: pressure | ||
| b. | Sound, P-waves | ||
| 2. | Audible: 20-20,000 Hz | ||
| 16.2. | Speed v=sqrt (B / ρ) and Frequency | ||
| 1. | Air at 1 ATM, 0 C: 331 m/s | ||
| 2. | Air at 1 ATM, any T: 331*sqrt[T(K) / 273] m/s | ||
| 3. | Fresh water at 25 C: 1490 m/s | ||
| 4. | Pretty much independent of frequency | ||
| 16.4. | The Doppler Effect | ||
| 1. | Motion changes wavelength and/or perceived frequency | ||
| 2. | frec = fsrc(v + vrec) /(v - vsrc); positive moving closer | ||
| 16.6. | Perception | ||
| 1. | Pitch: frequency, not wavelength | ||
| 2. | Loudness: log(intensity = power/area); depends also on frequency | ||
| 3. |
Timbre: presence of harmonics page 1, page 2 | ||