7&8: Acoustics, Resonance, and Waves in Nature

Building acoustics

Total sound effect in enclosed spaces.

Reverberation Time

Time for sound to drop by 60 dB.

Direct sound

Sound originating directly from the stage.

Early reflections

Initial echoes that enhance sound clarity.

Subsequent reflections

Later echoes that should be minimized.

Damping

Amplitude reduction due to energy absorption.

Resonance

Frequency matching between wave and medium.

Resonant frequency

Frequency at which materials vibrate easily.

Mechanical resonance

Energy transfer causing large vibrations.

Sympathetic vibration

Response to matching resonant frequency.

Aeroelastic flutter

Large vibrations from wind energy exceeding damping.

Mass dampers

Devices reducing vibrations in tall structures.

Seismic waves

Waves carrying energy through the Earth.

Primary waves (P-waves)

Longitudinal waves moving through solids and liquids.

Secondary waves (S-waves)

Transverse waves moving only through solids.

Echolocation

Locating objects via sound echoes.

Dolphin echolocation

Using sound to navigate and find prey.

Bat echolocation

High frequency pulses for navigation and hunting.

Concave surfaces

Reflect sound to a single focal point.

Convex surfaces

Spread sound out over a wider area.

Parabolic shape

Used in band shells to direct sound.

Tacoma Narrows Bridge

Collapsed due to resonance on November 7, 1940.