1. What is a sound?
Sound is a pressure wave in air or any other material medium.
The human ear and brain working together are very good at detecting and decoding patterns of information in sound (e.g., speech and music)

2. Sound in Air:

3. Sound in Air:

4. Sound in Air:

5. Sound in Air:

6. Sound in Air:

7. Sound in Air:

9. How do things make sounds?
Vocal Cords vibrate air by vibrating back and forth as air is exhaled.

10. How do things make sounds?
Vocal Cords vibrate air by vibrating back and forth as air is exhaled.

11. How do things make sounds?
Pianos “hammers” hit strings inside the piano vibrating them back and forth.

12. How do things make sounds?
String Instruments vibrate air when the string vibrates back and forth when plucked or bowed.

13. How do things make sounds?
Drums vibrate back and forth when struck with a hand or stick.

14. Characteristics of Sound:
Frequency – the more waves per second a sound has, the higher the pitch
High Frequency  High Note
Low Frequency  Low Note

15. Characteristics of Sound:
Amplitude - the taller the waves, the louder the sound
Low Amplitude  Soft Sound
High Amplitude  Loud Sound

16. Characteristics of Sound:
The speed of sound in air is constant
The speed of sound in air  343 m/s
Most humans can hear frequencies between 20 Hz and Hz
Wavelength is from meters and 17 meters.

17. Wave Characteristics:
f = frequency units: Hz (Hertz)
λ = wavelength units: m (meters)
v = speed units: m/s
v = f ∙ λ f = v ÷ λ
λ = v ÷ f

18. Unknown Equation Solution
A sound wave has a wavelength of 0.2 meters. What is its frequency in Hz?
Given
Unknown
Equation
Solution
f = v ÷ λ
f = 343 ÷ 0.2
f = 1715 Hz
f = v ÷ λ
f = ?
λ = 0.2 m
v = 343 m/s
Scientific Units

19. Unknown Equation Solution
A sound wave has a frequency of 600 Hz. What is its wavelength in meters?
Given
Unknown
Equation
Solution
v = 343 m/s
λ = v ÷ f
λ = 343 ÷ 600
λ = 0.57 m
λ = v ÷ f
λ = ?
f = 600 Hz
Scientific Units