A highly relatable tale: You're onstage during soundcheck or in the studio, and you find yourself trying to describe a sound to the engineer in charge of whatever you're working on. It's at that point you find yourself at a loss for words on how to describe that high-pitched, squealy thingy the synth is making, or that flabby, meedley-deedley sound from the guitar. How do you put into words that thing that defies description, or perhaps even defies imitation? This quick guide is your crash course to the world of sounds, and how to refer to them and talk about them.
What is a frequency?
Usually, when we describe sounds in the audio world and talk about where they reside in pitch (low to high), we refer to them in terms of their frequency. Sound is a wave, a movement of air molecules that our brain translates into sound through a surprisingly complicated series of workings within our ears. These waves can be measured by how many times they complete a cycle in a second. (Is that day in high school physics class starting to come back to you now?) We measure these cycles per second in a unit of measurement called hertz (Hz). In music, particularly in tuning, we refer to the reference pitch A440, which is 440 Hz. This is the note that produces a vibration that cycles at 440 times per second.
So, now that we know what these numbers and notes mean, where do we go from here?
The range of human hearing
The widely accepted range of human hearing stretches from 20 Hz all the way up to 20,000 Hz (or 20k Hz). While most of us are born with this range, most adults actually have a range of 20 Hz to 15k or 16k Hz (barring no high-frequency-specific hearing loss). This sounds astronomical still, but the scale of frequencies doesn’t divide itself evenly. For example, to go up an octave, you need to double the frequency; to go down an octave, you need to halve the frequency. The A above middle C on the piano is 440 Hz, and the A the next octave above is 880 Hz, but the A the octave below middle C is 220 Hz. This means that there's only one octave of notes (12 half-steps) between 10,000 Hz and 20,000 Hz, yet also only an octave between 80 Hz and 160 Hz.
Now we know how we measure sounds, and what the playing field is for what we can hear. But how do we describe these sounds?
20 to 80 Hz
This range is your true low end. The bottom half of this range (20 Hz to 40 Hz) is more felt than heard. In this range, it can be very hard to discern a true pitch. Most speaker systems, even high-end studio monitors, don't even produce sound accurately in this range, if at all. For reference, an Imperial Bosendorfer extended grand piano starts at the note F0 (21.8 Hz fundamental) and your normal concert grand starts at A0 (27.5 Hz fundamental) – and even those notes are hard to tune at their fundamental. The upper half (40 Hz to 80 Hz) is where the lowest note of the four-string bass (fundamental E at 41 Hz) comes into play. This is that rumbly bottom end you feel in your chest when you hear it.
80 to 160 Hz
This is where we enter what is commonly considered the bass range. Around 80 to 120 Hz is where most consumer-grade mixers with fixed EQ points and home stereos set their "low" band. We now see the guitar enter the spectrum here (low E string in standard tuning is 82.5 Hz fundamental), and the bass actually begins its exit at its fundamental pitch (G string open fundamental is 98 Hz). This range, when boosted, is where things can feel boomy or thumpy, but also adds warmth. For example, that big kick you feel in a dance club when the beat is thumping away tends to live around 100 to 120 Hz. Not enough in this range on low-end instruments (bass, kick drum, piano, synths) can lead to them feeling thin and anemic. Really powerful, rumbling, low-sounding feedback from monitors in a stage setting tends to live in this range.
160 to 500 Hz
We actually cover a lot of ground in this range. A lot of people who are new to thinking of sound in terms of frequencies think low frequencies are actually lower than they are and high frequencies are higher than they are. In this range, we see the guitar start to disappear at its fundamental frequency (high E string open fundamental is 330 Hz). But 200 to 250 Hz is a double-edged sword; this is where things can sound really warm and sweet, but too much and you get that muddy feeling, like when you have a cold and your voice sounds muffled in your own head. Simply said, a build-up of 200 Hz is a head cold. Above this, 250 to 500 Hz is where things can sound boxy (yes, this is a commonly accepted term). Imagine the woody ring when you hit or knock on a hollow box. It's not as low and muddy as the "head cold," but it's similar. This is where you're looking for issues with that.
500 to 1.6k Hz
We're now entering mids to upper-mids territory in the consumer EQ sense. The guitar is completely out at its fundamental pitch, with the highest of frets being around 900 Hz. This 500 to 900 Hz range is where too much can make things honky or nasal. The audio aid for this range is the teacher from the Charlie Brown cartoons. That feeling you get with that "wha wha" sound is what a build-up in this band will feel like. Above this is where you find sounds that start to get more pointed and sharp-sounding – for example, the sound that goes along with the TV test pattern (imagine your local public access channel when it's off the air). Well, the sound that accompanies that, the "beeeeeep," is a pure sine wave at 1,000 Hz. So if you hear something that brings that same irritation with it, or feedback that sounds close in pitch to it, you're now somewhere in the 1k Hz to 1.6k Hz range.
1.6 to 4k Hz
This range is where the "presence" in the human voice lies. If things sound dull or flat, a boost around this range (usually around 3k Hz) will liven them up. However, we find the Goldilocks scenario that all sound techs live with: too much of a boost in this range, and sounds become harsh and edgy. We also finally lose the fundamental pitches of the piano here, with the highest of keys usually checking out at around 4k Hz. That same presence element we find in the human voice also lies here in guitars as well, often competing for the same sonic territory. There's a reason lead vocalists and lead guitarists tend to feel at odds with each other not only for stage presence, but also for the same sonic space.
4 to 10k Hz
Welcome to the high end of things. Our home hi-fi and consumer high EQs hang out somewhere up here. (Remember, we're only dealing with about an octave in this range.) Sounds up here tend to be of the hiss and squeal variety – you know, the painful kinds. Sibilants like the S's of words are what tend to live in this range. Without them, things sound undefined or lack a certain crispness. The sizzle from cymbals and other percussion is present around 7k Hz to 10k Hz. Shrieking, piercing feedback, or a real crunchy, tinny quality to sounds can be addressed in this band.
10k Hz and beyond
These are the extreme highs. This is where frequency response starts to experience dropouts like it did in the low end, but for the opposite reasons. Sometimes it's because the transducer of a microphone may not be able to accurately respond to these frequencies, but sometimes it's because people can literally not hear things going on in this range. (High-end hearing in this realm is usually the first to go.) These frequencies can best be described as "air." That heady, open quality to a sound usually results from good representation of overtones in this range. Now, before you go pegging out all your EQs at 10 to 12k Hz to add airiness, also understand that simply boosting this range won't give you anything but noise if nothing exists there to begin with. For example, jingle a set of car keys. That really crispy, bell-like quality of the keys hitting one another is what we refer to in this air range. Can’t hear it? Don't worry, I know a number of incredible mix engineers who I'm nearly positive are deaf to anything above 14k Hz, and they still do incredible work. (The science behind why that's the case is actually incredibly complex, and I already fear I may have passed the saturation point for most Twitter-generation audiences... so perhaps in another post.)
I hope that this breakdown will begin to help you describe what you hear and define how you hear it. At the very least, you may now understand why some sound techs roll their eyes at you when you ask for more "highs" in your monitor mix – it's not actually that simple.
Aaron Staniulis is not only a freelance live sound and recording engineer, but also an accomplished musician, singer, and songwriter. He has spent equal time on both sides of the microphone working for and playing alongside everyone from local bar cover bands to major label recording artists, in venues stretching from tens to tens of thousands of people. Having seen both sides at all levels gives him the perfect perspective for shedding light on the "Angry Sound Guy." You can find out more about what he’s up to at aaronstaniulis.com.