What is a microphone’s frequency response and why is it important to know?
Frequency response is often presented as the range of frequencies that the microphone can “hear” and reproduce.
As you may know, the typical human ear, at birth, can hear sounds ranging from 20 to 20,000 Hz, though that ability may decrease for various reasons as a person ages. Many microphones have a frequency response that falls within that same 20–20,000 Hz range. While possible, it is rare for a microphone’s frequency response to exceed that range of human hearing. However, some microphones may intentionally attenuate frequencies on the low end in order to reduce rumble. Vocal microphones, for example, often cut out – or include a switch for the choice to cut out – frequencies 80 Hz and below. Other microphones may intentionally attenuate higher frequencies to reduce unwanted high-frequency noise. The low and high ends of the frequency response are important factors to consider when selecting microphones for particular applications, or when you know which frequencies you want to accentuate or avoid.
Frequency response is also commonly represented by a graph that is similar to an equalization curve. This graph shows the relation of the X axis (horizontal) frequencies to the Y axis (vertical) fluctuation of voltage (volume.) You may follow the measured response along the entire span of the frequencies. This will allow you to identify which frequencies are accented or diminished. For instance, in looking at the example below of the AT5045, you can see that there is a slight increase in volume around 5 kHz, a characteristic that is often used to emphasize presence. Again, such information can be important when choosing microphones for particular applications, or when you know which frequencies you want to accentuate or avoid.