1. Chapter 2
Sound
Subject : Physics
Teacher : Piyanuch Plaon

2. Sound
Energy is transferred from particle to
particle through matter.
How we hear?

3. Video about How we Hear?

4. How we hear?
a. Outer ear collects
sound.
b. Middle ear amplifies
sound.
c. Inner ear converts
sound.

7. Longitudinal Wave (คลื่นตามยาว)
wave particles vibrate back and forth along the path that the
wave travels.

8. Transverse waves (คลื่นตามขวาง)
wave particles vibrate in an up-and-down motion.

9. Parts of a Longitudinal Wave
Compressions
Rarefactions

10. Rarefactions (ส่วนขยาย) are regions of low air pressure
Compressions (ส่วนอัด) are regions of high air pressure
Compressions
Rarefactions

11. Sound Waves
• Like other waves, a sound wave can be
described by its wavelength and frequency.
• Wavelength is the distance from one
compression to another or one rarefaction
to another.
• The frequency of a
sound wave is the
number of
compressions or
rarefactions that
pass at a given
point in one second.

12. Sound waves also reflect,
refract, diffract, and interfere.

13. Propagationof sound
Medium (ตัวกลาง)
- Material that sound waves can travel
through.
- It can travel through solids, liquids and
gases but not through a vacuum.

14. The Speed of Sound
• The speed of sound is usually fastest in
solids, where molecules are closest together,
and slowest in gases, where molecules are
farthest apart.

15. Speed of Sound
Depends on:
1. Type of medium (ชนิดของตัวกลาง)
- travels better through liquids and solids
and gas
can’t travel through a vacuum.
2. Temperature of medium (อุณหภูมิของตัวกลาง)
- travels faster at higher temperature.
3. Density (ความหนาแน่น)
- sound moves well through dense materials.

16. Video about relation between amplitude and frequency

17. Intensity and loudness (ความเข้มเสียง และความดัง)
1) Intensity depends on the energy in a sound wave.
2) Loudness is human perception of intensity.
3) Loudness is measured on the decibel scale.
Properties of sound

18. Amplitude and Energy
• Sound waves with greater amplitude carry
more energy and sound louder.
• Sound waves with smaller amplitude carry
less energy and sound quieter.
• The higher the amplitude of the wave is, the more
compressed the particles in the compression are
and the more spread out they are in the rarefactions.

20. Relation between amplitude and loudness

21. - High frequency means more vibrations hitting
the ear.
- Pitch is how high or how low a sound seems to be.
- Healthy humans can hear from 20 Hz to 20,000 Hz
- We are most sensitive from 440 Hz to 7,000 Hz.
Frequency and pitch

22. Relation between frequency and pitch

23. - Ultrasonic sound has a frequency greater than
20,000 Hz.
a) Dogs (up to 35,000 Hz) b) Bats (over 100,000
Hz)
- Infrasonic sound has a frequency below 20 Hz
Frequency and pitch (Con.)

24. Range of frequency