sound

Last updated 2023.02.16 Edit Source

• Physics
• Wave
• Oscillaiton
• Equation

Sound is a longitudinal wave spreading in a flexible medium that is perceivable by the ear. (human sound)

Pitch is determined by frequency

ear -(reflection)→ ear canal → eardrum → ossicles (amplification and limiting force) → oval window → cochlea (different parts resonate at different frequency)

frequency: pitch
amplitude: loudness
overtones: timbre

infrasound: <20 Hz
ultrasound: >20 000 Hz

Mexican wave in stadium
$C=480m$
$t=40s$
$$c=\frac{s}{t}=\frac{C}{t}=\frac{480}{40}=12m/s$$
$$N=\frac{40s}{5s}=8$$

Sting oscillated
4 antinodes
$L=9m$
$f=2Hz$
$$\lambda=4.5m$$
$$c=\lambda \cdot f=4.5\cdot 2=9m/s$$

Distance from lightning calculated by the time difference between sound and light
$c_{light}=3\cdot 10^8m/s$
$c_{sound}=340m/s$
$s=2km=2000m$
$$t_1=\frac{s}{v}=\frac{2000}{3\cdot 10^8}=\frac{2}{3}\cdot 10^{-5}s$$
$$t_2=\frac{s}{v_2}=\frac{2000}{340}=5.9s$$
$$\Delta t=5.9s$$