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20 Cards in this Set
- Front
- Back
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What is sound? |
Longitudinal waves that propagate through a medium (usually air) |
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Describe the propagation of sound waves through the medium's elements? |
The displacement of the medium's elements are in the direction of the propagation of the wave |
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What is the difference between the propagation of sound waves and between transverse waves? |
The displacement of the medium's elements are in the direction of propagation of the sound wave -With transverse waves, the displacements are perpendicular to the wave propagation direction |
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How is pressure measured and what does it correspond to? |
In pascals 'Pa' -Corresponds to a weight of one newton applied to an area of one metre squared. |
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Describe atmospheric pressure |
-Caused by the weight of the atmosphere on the ground -approximately 100kPa (10^5Pa) |
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What is the pressure of a sound wave that is just audible? |
2 x 10^-5 Pa |
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How fast do pressure waves propagate in air? |
At about 340ms^-1 -Independent of their amplitude, wavelength, or frequency |
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What is the amplitude of a pressure wave |
The maximum displacement from the rest position |
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What is the wavelength of a pressure wave |
Distance between successive compression maxima |
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What is the frequency of a pressure wave |
Time between repeats |
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What is the propagation speed through water |
About 1500ms^-1 |
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How is the amplitude of a sound often measured? |
On a logarithmic scale in decibels -Change in pressure is measured relative to a reference level (frequently a notional threshold of human hearing) -Taking the base-10 logarithm of the ratio of the intensities -Multiplying the result by 20 to give the sound pressure level (SPL) |
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What is the equation for SPL? |
SPL = 20 log(10) p/pref |
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What is the logarithmic scale of amplitude good for? |
-Convenient for expressing the range of amplitudes in sound waves -Approximates how people hear loudness |
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What range does sound lie in for amplitude? |
Most sound lies within the range 0-100dB |
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What effects will sound waves also undergo? |
Refraction, diffraction, reflection, interference |
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What is refraction of a wave? |
When the medium characteristics change |
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What are the 3 sections of the ear? |
The outer ear, inner ear, and middle ear |
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What does the outer ear consist of? |
-A flap of skin called the pinna, the auditory canal (a 3cm-long tube) which leads to the tympanic membrane or the ear drum |
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What is the primary function of the pinna and opening into the auditory canal? |
To assist the hearing system to deduce the direction of a sound source |
