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Microphone frequency response and how to check those charts.

Microphone frequency response and how to check those charts.The selection of a microphone should be decided on many factors and one of the most important factors is the frequency response of the microphone compared to the required application. This can be a bit daunting for the newcomer especially when you need to look at, and decipher, microphone specifications. Even those who know about sound systems and what they like to hear can sometimes struggle with microphone selection.

Frequency response of a microphone is normally provided by the manufacturer and the results are normally plotted on a graph. The testing procedure is generally completed in an anechoic chamber, which is a dedicated room that has been constructed specifically for testing purposes and uses acoustic treatment to create the perfect testing environment. The room is completely dead, from an acoustic point of view, and therefore makes the testing of all microphones equal as there are no sound reflections to cope with. The test procedure uses a loudspeaker positioned in front of the microphone and pink noise is played back, we'll explain pink noise in another blog post. The audio picked up by the microphone is then routed to processing equipment which analyses the pickup of the microphone and produces data that is then plotted on the microphone frequency response graph. The test and subsequent graphs are normally produced using a frequency response range covering 20Hz to 20kHz to make sure the range of human hearing is covered.

The actual graph itself (example shown) is presented on a logarithmic scale which is why the vertical lines aren't equally spaced. Across the X axis on the bottom you can see numbers under some of the lines, these show you the frequency in Hz. The Y axis runs vertically up the side and the numbers on this axis are the audio level in decibels (dB). You can now see how you can reference a particular frequency against its relative audio level.

Now you've seen a graph how is this helpful to you? As you can see on the graph the microphone starts to ramp up from 50Hz to 100Hz then everything goes nice and flat from 100Hz up to about 1kHz (1000Hz), then you get a bit of a hump until it drops down between 7kHz and 8kHz before a last small hump up to 10kHz where it finally tails off as it heads towards 20kHz. The graph shown is for the legendary Shure SM58 and the spec sheet says it has a useable frequency response of 50Hz to 15kHz and now you can see how this is obtained as below 50 Hz and above 15kHz the microphone basically doesn't respond. So looking at this chart you can see that applications that require a nice flat response between 100Hz and 1kHz would be ideal for this microphone but it is even more suited to producing great vocals as the microphone has a roll of for the bass frequencies and becomes particularly bright in the mid-range and higher frequencies.

Hope this was useful for you and we'll soon start looking into microphone polar patterns so keep coming back to check or follow us on Twitter and Facebook.

*Thanks to Shure for the image

Created On  29 Jan 2018 9:46  -  Permalink


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