Frequencies are designated in Hz, which is an abbreviation for Hertz (the unit of measurement of the frequency in cycles per second). A frequency range of 30Hz to 30kHz covers the range of very low sounds (such as a string bass or contrabassoon) to very high sounds (such as the overtones of a piccolo).
Frequency response refers to the way a microphone responds to different frequencies over its specified operating range.
In the image below you can see what types of sounds are present at various frequencies.
Recent scientific research has shown that music has high frequency overtones as high as 100kHz. Most humans can only hear pure tones to 15kHz or 20kHz. However, this research shows that overtones above 20kHz contribute to the sound quality, or timbre, of sound that we hear or perceive. Some Earthworks microphone models have a frequency response up to 50kHz. You can read the technical paper ‘The World Beyond 20kHz’ written by David E. Blackmer to learn more about extended frequency response.
A flat frequency response means that the microphone is equally sensitive to all frequencies over its entire operating range. A flat frequency response insures that no frequencies are exaggerated or attenuated, resulting in a more accurate representation of the original sound.
Again, the Frequency Response indicates the accuracy of a microphone within its specified operating range (i.e. where the bumps and dips are).
However, Frequency Range is different, as it defines the operating range of a microphone and indicates the lowest and highest frequencies that a microphone will capture. For example, a microphone that has a frequency operating range of 30Hz to 40kHz can reproduce all frequencies within this range. Frequencies outside this range will be reproduced at a much lesser extent or not at all. A microphones frequency operating range is typically indicated in the print specifications, while its frequency response is normally shown on a graph such as the Earthworks SR40V response chart pictured at the right.