Understanding Microphone Frequency Response

If you’ve ever looked at a microphone’s frequency response chart and thought, “Nah, I’m good,” this is for you.

Even though they look like something out of a college physics textbook, frequency response charts are really pretty simple. The x-axis represents which frequencies a microphone can pick up—with low frequencies on the left side and high frequencies to the right— and the y-axis shows the loudness of those frequencies relative to one another.

In this article, we’ll explain some frequency response basics so you can easily understand the differences between microphones and make informed decisions when selecting the best mic for a particular source.

What Are Frequencies, Anyway?

To answer that question, let’s take a step back and ask ourselves, well, “what is sound?”

In its most basic form, sound is any vibration that travels through matter—solid, liquid, or gas.

When we measure sounds, we most often speak in terms of amplitude and wavelength.

A sound’s amplitude is its volume, expressed in decibels (dB). Frequency, (or wavelength) expressed in Hertz (Hz), is a measure of how slow or fast a sound source is vibrating. Longer wavelengths mean slower vibrations, which produces a low pitch. Shorter wavelengths create faster vibrations with a higher pitch.

Reading A Microphone Frequency Response Diagram

When we look at a microphone’s frequency response chart—let’s use the Yeti, just for kicks—we can see frequencies listed in Hertz horizontally from low-to-high along the x-axis and their relative amplitude(s) expressed in decibels vertically along the y-axis.  

Figure 1 — Yeti Frequency Response Chart

If we look at the topmost dotted line, which represents the Yeti’s frequency response in Stereo Mode, we can see that it’s quite a bit louder than the other modes. The frequency response, however, is much the same in Stereo Mode as the other modes, with a low frequency roll-off at around 120Hz and below, a relatively even response between 120Hz and 2kHz, and a treble boost between 3kHz–6kHz. Why is that?

Since the Yeti is designed to record musical instruments, speech, or anything else within audible range, it’s built with a frequency response of 20Hz–20kHz, covering every frequency that humans can hear.

Most musical instruments, however, produce tones between 44Hz—the pitch of a bass guitar’s open low E string—and 14kHz, which you might hear as the metallic top end of cymbals or as sharp “S” and “T” consonant sounds on a vocal track.

The Yeti’s frequency response is custom-tailored to music and speech right out of the box. It rolls off bass frequencies that build up and create a muddy mix, remains neutral throughout the midrange to preserve accuracy, has a slight treble boost for presence and intelligibility, and finally, a minor taper at the highest frequencies for a sound that’s bright and defined, but not shrill.

Musical Instrument Frequency Ranges

To give you an idea of the frequencies you’ll most often deal with whether you’re recording a podcast interview, filming a YouTube video, or mixing an album, here is a quick reference guide to get you started.

Sub Bass: 40Hz and Below

Besides the extreme bass frequencies on a kick drum, there isn’t much musical information hanging out down here. Synthesizers, of course, can produce sub bass frequencies, and Hollywood movies will use the “LFE” (Low Frequency Effect) to enhance action scenes with subsonic energy, but most recordists will cut these frequencies out.

Bass: 40Hz–200Hz

The bass register contains the fundamental frequencies that help us tell the difference between notes in a melody. It’s also where you’ll find the low keys on the piano and the low notes on a bass guitar. It’s rare for vocalists to sing in this range, but baritone singers can go as low as 100Hz, though most pop singing happens in a higher register.

Low Mids: 200Hz–500Hz

The low mids are the most powerful frequency range of the human voice, but too much information in this area can make singers or voiceovers sound muffled and boxy. Too little, and you’re left with a recording that sounds hollow and lacks punch. In fact, most musical instruments operate in this space, so you’ll spend a lot of time listening here.

Mid Range: 500Hz–3kHz

Human ears are most sensitive to the frequencies in this area which contain most of the musical information we hear on our speakers. The microphone on your phone or tablet operates almost exclusively in this range, which makes it awesome for phoning home, but not so great for recording demos.

Presence: 3kHz–7kHz

True to its namesake, this is where vocals, guitars, woodwinds, piano, and percussion have, well…presence. These frequencies help instruments or vocal narration cut through a dense mix of backing tracks and sound effects.

Treble: 7kHz–14kHz

Frequencies way up here in the treble band are what give cymbals their sizzle and snare drums their snap, but too many treble frequencies can make recordings harsh, unpleasant, and tinny.

Air Band: 14kHz and Above

Even though humans can technically hear frequencies all the way up to 20kHz, most of us have been rockin’ long and loud enough that the upper limit of our hearing tapers off somewhere between 14kHz–16kHz. Luckily for us, there isn’t much musical information above 14kHz, anyway. But even if some of us are unable to actually hear these frequencies, we can still perceive them when we appreciate the airy, hi-fi sheen of a great string quartet recording. These frequencies are crucial because they contain the harmonic overtones that make classic albums sound larger than life. You’ll miss them when they’re gone.   

Now that you’re a professional microphone frequency finder, you can interpret a microphone’s frequency response chart to choose the best mic for the job and make clean, professional recordings without the need for external equalizers. For more recording tips, check out our blog.