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Flashcards in Sound Deck (14):
1

Infrasound vs Ultrasound


  • Vibrations whose frequency is too low to hear is called infrasound. 



  • Vibrations whose frequency is too high to hear is called ultrasound.
     

2

Rank of speeds in solids, liquids, and gases

Speed of sound in solids > liquids > gases.

3

Speed of sound in stiff vs compressible objects


Speed of sound in stiff objects > compressible objects.
 

4

Speed of sound in less dense vs more dense objects


  • Speed of sound in less dense objects > more dense objects. 

  • Even though gases are less dense than solids, sound still travels slower in them because they are too compressible.
     

5

Speed of sound in hot objects vs cold objects


Speed of sound in hot objects > cold objects.
 

6

Intensity of sound


β = 10 logI/I0 




β is sound level in decibels. I is intensity. I0 is 10-12 W/m2
 

7

Attenuation


  • Sound attenuation is the gradual loss of intensity as sound travels through a medium. 



  • Sound attenuation is the greatest for soft, elastic, viscous, less dense material.
     

8

Situations where the observed frequency is higher than the actual:


Source moving toward stationary observer: fo = fs v/(v - vs) 




Observer moving toward stationary source: fo = fs (v + vo)/v 






Source and observer both moving toward each other: fo = fs (v + vo)/(v - vs)
 

9

Situations where the observed frequency is lower than the actual:


Source moving away from stationary observer: fo = fs v/(v + vs) 




Observer moving away from stationary source: fo = fs (v - vo)/v 






Source and observer both moving away from each other: fo = fs (v - vo)/(v + vs)
 

10

Pitch


  • Pitch is the human perception of the frequency of sound. 



  • Higher frequency = higher pitch.
     

11

Frequencies can be obtained by:

f = v/λ

12

Both strings and pipes open at both ends have Length = 

 L = (n/2)λ

13

Pipes with a closed end have L =

((2n-1)/4)λ

14

Three fundamental properties of sound

reflection, refraction, and diffraction.