microphone converts the mechanical wave energy into electrical energy the mechanical energy
is the sound pressure level at the diaphragm of the microphone and it is measured in
decibel or pascals the electrical energy is in the form of output voltage and it is measured in milli
volt or decibel volt therefore sensitivity is the efficiency of microphone in
converting the sound wave into output electrical voltage the sound pressure level increases
when the sound gets louder so for the same loudness a higher sensitivity microphone
will produce a higher output voltage to be able to compare two microphones sensitivity
the microphone manufacturers use one pascal sound pressure with a standard one kilo hertz
sine wave and then measure the output voltage in Europe this output voltage is directly classified
as microphone's sensitivity and its unit is millivolt per pascal in another words
it shows how much voltage you get for applying one pascal sound pressure sensitivity is also known as
transfer factor therefore I will use transfer factor to refer to the European sensitivity
in the USA the sensitivity is a comparison between a hypothetically high efficient microphone
and a transfer factor the highly efficient microphone is assumed to produce one volt
for one pascal applied pressure which is same as 1000 millivolt per pascal
therefore sensitivity in decibel relative to one volt per pascal is equals to 20 times log to the
base 10 of transfer factor divided by 1000 for example if you would look at my Sennheiser MKE 600
shotgun microphone transfer factor to calculate the American sensitivity value
if you would look at the spec you will find two different values one with p48 phantom powering
which gives 21 millivolt per pascal and a lower transfer factor of 19 millivolts per pascal
with battery powering it shows that the sensitivity changes with input powering using
21 millivolts per pascal and comparing it against a hypothetically high transfer factor
of 1000 millivolts per pascal we get a sensitivity of minus 33.56 decibel now I will artificially
increase the transfer factor of the mic from 21 to 50 millivolts per pascal and you can see that
its sensitivity has increased to -26 decibel note the lower the negative value of a number
means a higher number you might be wondering how we got decibel while there was no decibel
in the equation this is because one pascal is equals to 94 decibel the complete equation is
SPL in decibel is equals to 20 times log to the base 10 of the ratios of root mean square sound
pressure divided by reference sound pressure the following components of the microphone affect
its sensitivity number one the reactiveness of the diaphragm to various sound pressure levels
number two microphone type for example whether it's a dynamic or condenser mic
number three and finally the amplification of the audio signal within the microphone
the typical sensitivity of various microphones are as follows dynamic mic and passive ribbon
mic is equals to -60 to minus 44 decibel relative to one volt per pascal condenser mic and active
ribbon mic is equals to minus 42 to minus 30 decibel relative to 1 volt per pascal important
to remember that a higher sensitivity doesn't necessarily mean a better quality audio you need
to select a mic with a sensitivity that suits your application for example if you're recording low
volume sound sources you need a high sensitivity microphone otherwise in order to make the sound
audible you need to apply an amplifier which in turn would create distortion to the output signal
in contrast if you want to record a very high volume sound source a high sensitivity
mic could easily overload the pre-amplifier or mixer and hence producing distortion
high output impedance microphones have inherently higher sensitivity but as I have mentioned in my
video on output impedance the higher the output impedance the higher the risk for the worst
quality audio particularly if you are using a long audio cable connection I hope this video
helped you to better understand the microphone sensitivity if you have any questions please
let me know in the comments to learn more about microphones please watch my other videos in here
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