How we hear?
a. Outer ear collects
b. Middle ear amplifies
c. Inner ear converts
Longitudinal Wave (คลื่นตามยาว)
wave particles vibrate back and forth along the path that the
Transverse waves (คลื่นตามขวาง)
wave particles vibrate in an up-and-down motion.
Parts of a Longitudinal Wave
Rarefactions (ส่วนขยาย) are regions of low air pressure
Compressions (ส่วนอัด) are regions of high air pressure
• 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
• The frequency of a
sound wave is the
pass at a given
point in one second.
Sound waves also reflect,
refract, diffract, and interfere.
- Material that sound waves can travel
- It can travel through solids, liquids and
gases but not through a vacuum.
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
Speed of Sound
1. Type of medium (ชนิดของตัวกลาง)
- travels better through liquids and solids
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.
Video about relation between amplitude and frequency
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
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.
- High frequency means more vibrations hitting
- 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