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Chapter 11+12: Waves and Sound by Mind Map: Chapter 11+12: Waves and Sound
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Chapter 11+12: Waves and Sound

Intensity: measure of power/unit

decreases as the distance from source increases

Wave: disturbance that travels away from its source

Transverse (S)


Ex: Seismic

Longitudinal (P)


Ex: Seismic, sound

Periodic Wave

Frequency: Occurence of pattern repeating

Inverse of period

Repeats the same pattern

Period: time is takes for one wave

Amplitude: height of wave

Wavelength:distance of wave travel

Additional Wave Properties

Reflection of waves: ave with an abrupt boundary between mediums

Refraction: Change in propagation direction

Compression: waves are bunched

Rarefaction: Waves are spread

Multiple Waves


Destructive: waves 180 degrees out of phase

Constructive: waves in phase of eachother

Incoherent: phase relationship varies randomly

Coherent: same frequency and fixed phase

Main Properties:

mass density increases=decrease in speed

Increase in tension=increase in speed

Standing Wave

One wave is reflected and interferes with incident wave

Anti-Node: halfway in between nodes

Node:Halfway between points of max. amplitude

Fundamental Frequency: lowest freq. standing wave

Sound Wave

Uniform distribution of molecules is disturbed

Frequencies of sound wave

Audible range: 20Hz-20kHz

Infrasound: below 20Hz

Ultrasound: abover 20kHz

audible range varies with animals

Speed of sound wave

Square root of Frequency/linear mass density

Increases .606m/s per each degree C increase

Speed of sound at room temp (293K): 343 m/s

Intertia: characterized by mas density

Speed of sound at 273K: 331 m/s

Amplitude + Intensity of Sound wave

Pressure Amplitude

Pressure fluctuation above/below pressure in absense of wave

Displacement Amplitude

mas. displacement of an element of medium from equilibrium

Intensity is proportional to amplitude squared

Threshold of hearing:reference intensity with intensity level

1E-12 W/m2

Intensity increase of a factor of 10; 10dB added

Intensity Unit: decibels

Standing sound waves

Pipe closed at one end

Wavelength: 4L/n

Closed end: pressure antinode + displacement node

Pipe open at both ends

Same boundary condition at each end


Open ends: pressure nodes + displacement antinodes

Timbre/Tone Quality

Harmonics:fundamental and overtones

Overtone: frequencies that are not the fundamental