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page 186

type

sense element

freq. range

temp. & humidity stability

 

 

 

 

1. condenser

capacitive

2Hz-20KHz

fair

2. ceramic

piezo-electric

20Hz-10KHz

good

3. dynamic

magnetic coil

25Hz-15KHz

good

• A microphone has a finite area to measure the sound with. As the diameter ‘d’ approaches the wavelength of sound, the sound becomes distorted.

d << c/f = λ for good measurement

When wind blows across a microphone, it generates a low frequency turbulence noise. This is often corrected by using dBA measurements, and foam balls.

Corrections must also be made for changes in temperature and altitude

 

 

 

 

 

 

1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

460 + F

--

 

 

C

 

= 10log

 

2 30

 

dB

 

 

 

------------------

-----

 

 

TP

 

 

528

B

 

 

Barometric pressure (in Hg) temperature (F)

correct level to measurement

13.11 LIGHT INTENSITY

13.11.1 Light Dependant Resistors (LDR)

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