LESSON 03
Properties & Detection of Sound
How sound travels and how we hear it.
Frequency1.00×
Amplitude1.00×
Sound is a longitudinal wave — air particles compress and rarefy along the direction of travel. Without a medium, sound cannot exist.
Speed of sound
In air at 20 °C, sound travels ~343 m/s. It travels faster in liquids and solids because particles are closer together.
Detection
The ear converts pressure waves into vibrations of the eardrum, then into nerve signals. Microphones do the same with a thin diaphragm.
Loudness & pitch
Loudness depends on amplitude (measured in decibels). Pitch depends on frequency (Hz).
Key Formulas
Speed in air
v ≈ 331 + 0.6·T
T in °C, v in m/s
Real-life applications
- Ultrasound medical imaging
- Sonar in submarines
- Hearing aids
Summary
- Sound = longitudinal pressure wave.
- Needs a medium.
- Loudness ↔ amplitude, pitch ↔ frequency.
Check Yourself
Q1.Sound cannot travel through…
Q2.Pitch of a sound depends on its…