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Hearing
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When Intensity doubles
ouput level is increased by 3
When pressure is doubled
output level is increased by 6
Purpose of sound measurement
1. To calibrate audiometers
2. Assess background levels in audiometric test rooms
3. Identify hazardous noise exposure levels
Sound level meter (SLM)
• Picks up sounds of all frequencies within a certain range
• Determines the magnitude of the sound in dB SPL
Linear Setting
SLM measures overall SPL of sounds picked up by the microphone
Weighting Fliters
De-emphasizes low frequency sounds
octave-band analyzer
– Set of selectable Band-Pass filters
– Used to determine dB present for a given frequency bandwidth
C-weighting
Practically linear, virtually no weighting of spectrum in the greatest part of the audible range
B-weighting
some reduction of sound level at very low and very high frequencies
A-weighting
dramatic reduction of low frequency sound level
– e.g., sounds of 100 Hz are reduced by about 20 dB
Weighting Networks
A and C scales are most commonly used in noise measurement
A scale used to measure speech sound-closest to human hearing
Decible
a relative measure of sound level
– There is always a reference value
– Intensities/Pressure are compared to a standard reference value in the form of a ratio or fraction
– Physical magnitudes are stated in relation to a value that has meaning to us• See next slide for example
Equal ratios
become equal intervals on logarithmic scale
Author
cgray10
ID
40286
Card Set
Hearing
Description
unit 3
Updated
2010-10-06T23:10:47Z
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