1. Sound

2. Loudness --> Amplitude
Characteristics
Loudness --> Amplitude
Pitch -->frequency

3. Wave Formulas

4. Speed of Sound The speed of sound in air changes with temperature.
The speed at 0oC is 331m/s for dry air
It increase by 0.6 m/s for each degree Celsius above zero.

5. Echoes
An echo is a reflected sound wave
An echo is sent from and detected at the same location
An echo must travel the distance to the barrier two times to get back to the detector

6. Doppler Effect v = velocity of sound in air
vs = velocity of source (toward is +)
vd = velocity of detector (toward is +)
f = frequency emitted
f ' = frequency detected

7. Sound Intensity  = decibels (dB) P = Power of source (watts)
I = intensity (W/m2)
R= distance from source (m)
Io = W/m threshold of hearing
1 E -12 W/m2

8. A 20 dB increase = 10 times the pressure
Concepts
A 20 dB increase = 10 times the pressure
A 10 dB increase = twice the loudness

9. Remember units! Frequency -- Hertz (cycles/sec) Period -- seconds
Wavelength -- meters
Wave speed -- m/s
Intensity -- W/m2
Sound intensity level -- decibels (dB)

10. Harmonics and Overtones
1st harmonic = fundamental (f1) frequency
2nd harmonic = 1st overtone (f2)
3rd harmonic = 2nd overtone (f3)
4th harmonic = 3rd overtone (f4)
and so on...

11. Resonance and Fundamental Frequency in air columns (tubes)
Open ends have an antinode
Closed ends have a node
fundamental frequency is lowest frequency possible (lowest frequency  longest wavelength)
use length of pipe to calculate wavelength by relating the length to the number of wavelengths formed

12. Resonance in air columns (tubes) Remember: open endantinode, closed endnode
Fundamental frequency (1st harmonic) has 1 node
1st overtone (2nd harmonic)-2 nodes
2nd overtone (3rd harmonic)-3 nodes
and so on …
Assume speed of sound in air to be 343 m/s unless told otherwise (i.e. sound not in air or you are given a specific temp of air).

13. Resonance on Strings
Fundamental frequency has ONE antinode (L = /2) (or segment)
2nd harmonic (1st overtone) – 2 antinodes (L = ) (or segments)
3rd harmonic (2nd overtone) - 3 antinodes ( L = 3/2) (or segments)
4th harmonic (3rd overtone) - 4 antinodes ( L = 2 ) (or segments)
and so on…

14. Beats
Beats occur due to interference patterns between sound waves of different frequencies.
Sounds with frequencies separated by 7 Hertz or less will produce beats that can be detected by the human ear.