How to Read a Microphone Frequency Response Chart

While headphone and earbud packaging that boasts a frequency range outside your ability to hear sound is just, well, a marketing tactic, the same is not true of microphone frequency response charts. You can’t buy a microphone without running into a frequency response chart. Here’s why: A frequency response chart tells you a lot about which mic is appropriate for any given application and which mic is not. What if you don’t know what the chart means, though? Charts and graphs are intended to simplify an explanation, but sometimes, they can just cause more confusion.

Creating the Chart

A frequency response chart is generated by testing the microphone in an anechoic chamber. An anechoic chamber is a specially constructed room just for audio testing: a controlled atmosphere where the room is acoustically dead, without any form of sound reflection.

The Shure Anechoic Chamber

The Shure Anechoic Chamber

A mic is set up in front of the calibrated loudspeaker. Pink noise is played. (If you’re not familiar with the term, pink noise is all frequencies with equal energy in every octave.) The microphone signal is routed into a spectrum analyzer and a frequency response chart is produced.

Reading the Chart

The chart is usually over the 20 Hz to 20 kHz range, which is the range of human hearing. So, how do you read it?

The horizontal numbers in a microphone frequency response chart indicate frequencies (again, usually over the 20 Hz to 20 kHz range), and the vertical numbers represent relative output level in dB (decibels). As you look at a frequency chart, you can tell how a given microphone performs at certain frequencies.

Comparing Two Popular Shure Mics

How is this information helpful?  Let’s look at a couple of examples.

Here’s the ubiquitous Shure SM57’s frequency chart:

SM57 Frequency Response Chart

SM57 Frequency Response Chart

The frequency response of the SM57 makes it especially good for certain instruments such as a snare drum because the fundamental frequency of the snare resides in the 150 Hz to 250 Hz range, right where the SM57 frequency chart shows that the SM57 response is flat or neutral.

In other words, at this frequency, what you hear going into the microphone is what you will tend to hear coming out: nothing more, nothing less.

The presence bump on the right of the chart is just where the frequency of the “snap” of the snare resides. In addition, its rolled off low-end makes it great for downplaying the kick drum, which is often very close to the snare. This combination is what most engineers are looking for in a great snare drum mic: the ability to capture the true sound of the snare, accentuate its snap, and reject other instruments in close proximity.

Now, let’s look at another popular Shure mic: the BETA 58A®.

Beta58A Frequency Response Chart

Beta58A Frequency Response Chart

The BETA 58A is a popular model for vocals. The rising frequency response from 2,000 to 10,000 Hz adds brightness and intelligibility to the voice. The bass emphasis (proximity effect) when used close to the mouth—see the dotted lines in the graph—adds warmth and fullness to the voice.

Pairing the Mic with the Sound Source

Next, let’s look at what you’re planning to mic. Musical instruments and voices have frequency ranges as indicated on the chart below. The darker orange indicates the range of fundamental frequencies, and the lighter shade represents the range of the highest harmonics or overtones of the sound source.

A mic that responds evenly to the full range of an instrument will reproduce the most natural sound.

Vocal and Instrument Frequency Response Chart

Vocal and Instrument Frequency Response Chart

When you compare the frequency range of the SM57 to this chart, it’s easy to understand why it’s a staple in most mic lockers. Often called “the industry workhorse,” it does a very good job of capturing the natural sound of most instruments across their frequencies.

Need practice? There are hundreds of specification sheets for microphones on the Shure site. Using the instrument chart above, look at the frequency ranges on the spec sheets for a few different mics: maybe the PG56, BETA®181, or the “Thriller” SM7B for starters. We bet you’ll be able to match them to their most popular applications. Down the road, that may help you to choose the right mic for your particular application.

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Davida Rochman

Davida Rochman

A Shure associate since 1979, Davida Rochman graduated with a degree in Speech Communications and never imagined that her first post-college job would result in a lifelong career that had her marketing microphones rather than speaking into them. Today, Davida is a Communications Manager, lending her skills to a wide spectrum of activities, from public relations and social media to content development and sponsorships.

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  • helen hwang says:

    very good tutorial material.
    A question here, is it possible to extend the low end cut off frequency near “0” hertz? all just shift the band to left?

    • Davida Rochman says:

      Hi, Helen! Thanks for the question. I reached out to our Shure Applications Engineers to get a response:

      “This seems to be a two part question – 1) what is frequency? and 2) can you change the frequency response of a microphone?

      1) Zero Hertz would imply silence, as there is no sound reproduction at zero Hertz. Hertz represents frequency and frequency represents waveform development over time. Without getting into any math or too deep into physics, think about a waveform as a string suspended between two points. When the string is still and no movement, that would be the equivalent of zero Hertz, or silence. If you pluck the string and create movement, the amount of times that movement occurs between those two points would be the frequency, which is represented in Hertz.

      2) The frequency response and the “roll-off” circuitry of a microphone is fixed based on the design of the microphone, but roll off can be manipulated by equalizers and filters further down the signal chain. For example, if one were to use an Beta 52A on a bass drum that is especially resonant below 80 Hz and this was not desirable for the application, you could roll off those frequencies using a band pass filter, or equalizer. This is also true if higher frequencies are not desirable, except you can use a high pass filter or equalizer to adjust the roll off.

      Also, keep in mind that equalizers or other filters have no effect outside the specified frequency response of the microphone. For the Beta 52A mentioned below, the frequency response is listed as “20-10,000 Hz,” so using an EQ to boost frequencies at 12,000 Hz for that mic will have absolutely no effect.

      Lastly, human hearing, at its best, only covers 20-20,000 Hz. In our product line, the SM81 comes closest to covering this entire range with a reasonably “flat” frequency response. There certainly are microphones that respond to frequencies higher than 20,000 Hz, but we can’t hear anything up there – they are used as measurement mics, mostly.”

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