Sound Flashcards
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.
Rank of speeds in solids, liquids, and gases
Speed of sound in solids > liquids > gases.
Speed of sound in stiff vs compressible objects
Speed of sound in stiff objects > compressible objects.
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.
Speed of sound in hot objects vs cold objects
Speed of sound in hot objects > cold objects.
Intensity of sound
β = 10 logI/I0
β is sound level in decibels. I is intensity. I0 is 10-12 W/m2
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.
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)
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)
Pitch
- Pitch is the human perception of the frequency of sound.
- Higher frequency = higher pitch.
Frequencies can be obtained by:
f = v/λ
Both strings and pipes open at both ends have Length =
L = (n/2)λ
Pipes with a closed end have L =
((2n-1)/4)λ
Three fundamental properties of sound
reflection, refraction, and diffraction.
