Airy:  Spaciousness, often a pleasant mostly treble-based reverb sound.  Extended frequency response that runs up through the top end of the bandwidth.

Brittle:  Peaking in high-frequencies, weak fundamentals with slightly distorted or harsh highs.

Crisp:  Good high-frequency response with good transient quality

Crispy:  Constant, but perhaps random high frequency sounds not unlike frying foods.

Delicate: Extended high frequency range without being harsh.  Emphasis on high frequencies extending to 20 KHz, but without the peaking. 

Edgy:  High frequency emphasis from about 3.5 to 6 KHz with harmonic content overly strong in comparison to fundamentals.  Can deal with high frequency distortion and rasp.

Piercing:  Hard on the ears, screechy and sharp.  Narrow peaks occurring between 3 and 10 KHz.

Raspy:  Harsh sounds in the 6 KHz range that sounds like a scratchy voice.

Sibilant:  S and Sh sounds are overly emphasized. 

Sizzly:  Similar to crisp, like the sound of the decay on a riveted cymbal.

Steely or Shiny:  Lots of top end from 3-6 KHz with peaky highs (as opposed to flat but boosted top end)

Sweet:  Flat high-frequency response without distortion and extended the full bandwidth.  

The final section of the audible spectrum is the high frequency or treble portion. Humans theoretically are able to hear up to 20 KHz (that is, newborn baby girls can theoretically hear up to 20 KHz at normal listening levels; for the rest of us, considerably lower). So what could happen in the 16,500 Hz range if no new instruments can sound there? 

It contains almost nothing but upper harmonics of treble instruments and room tone.  This helps solo instruments and vocals sound present and full, but also adds brightness and clarity to a mix

Most telephones cut off around 3.5 KHz yet you can still tell whose voice it is on the phone.  This tells you that practically everything needed to understand and distinguish any audio content pretty much lives below this range.

Pretty much only dog whistles operate in this range, so there is absolutely no need to worry about any more fundamentals or really any lower order harmonics getting in the way of any treatment you decide to apply.

Boosting in this range again helps with upper harmonics and upper harmonics are important to our brains in calculating proximity.  The closer we are to something, the more detail we can hear in the sound.  Similarly, the quieter an environment is when a sound is made, the more apparent that sound seems to us.  The upper harmonics of a sound are generally very soft and are the first things to go when we are either far away from a sound source or it is sounding in a noisy environment.  As such, the more upper frequency detail we can hear, the closer our mind perceives the sound source to be.  Furthermore, we perceive upper harmonic detail as clarity and salience.

Many mastering engineers, as a final polish job, will use a very hi-fi shelving EQ and boost the frequencies from roughly 16 or 18 KHz up about 3 or 4 dB.  The difference can be quite astonishing.

This range also gives you airiness and some pleasant room sounds.  But boosting this range can also have negative effects like hissing, piercing, and sibilance.

Sibilance, which is an overemphasis on frequencies ranging roughly from 6-8 KHz, is by far the most apparent and troublesome.  The beast way to deal with this is with a de-esser rather than an EQ so as not to sacrifice the harmonic content that you like that isn’t abrasive.  A de-esser is a frequency-dependent compressor, it only compresses a narrow bandwidth, usually between 4 and 9 KHz to tame sibilance.  It can be adjusted to work on cymbals or even hiss if it has the proper variables.

Next week, I’ll examine some of the commonly used terms associated with high frequency content and that will wrap up my series on the Audible Spectrum.  I hope you’ve enjoyed it so far!

Bright:  Emphasis on high-frequencies, specifically upper-mids with emphasis on harmonics.

Crunchy:  Exists between 2K and 4K, typically distortion based and generally pleasant.  Can lend rhythmic distinction to distorted rhythm parts.

Detailed:  Minutiae of the music are easily audible.  Present sounding, intimate and close with lots of articulation and transient response throughout the upper mid range.

Forward:  Present, in your face.  Detail present in transients and upper harmonics which lends a feeling of proximity.

Glassy:  Brittle sounding, too much upper-mid content especially with regard to harmonics in relation to fundamentals. 

Grungy:  Lots of distortion with emphasis on odd harmonics.

Hard:  Excellent transient response combined with an overemphasis on upper-midrange frequencies.

Harsh:  Peaking in the 2-6 KHz range.

Metallic:  Emphasis on upper-mid range frequencies, specifically those that deal with odd order harmonics in this range.

Pinched:  Narrow-bandwidth, often relegated to the upper-mid range frequencies.  Try boosting lower frequencies to balance.

Consisting of frequencies from 1.2 to 3.5 KHz, we once again have a nice range of frequencies to play with.  The high-mids contain lots of harmonics, especially the lower to mid order harmonics for the mid-range instruments.  The range of  2300 Hz gives you plenty of room to work with in carving out specific places for various instruments to sit.  Only the highest instruments can really play in this range:  the piccolo can sound in this band and it also accounts for the top octave or so of the piano, which most people know not a whole lot happens there.  So there are no new instruments sounding fundamentals to get in the way and cover up the harmonic content that you are treating in this band.

Additionally, this range is very important because it contains much of the sudden transient content.  Attack transients, sibilance, consonants and more all live in this register, so it is very important for understandability as well as punchiness, presence, and dynamics. 

The human voice is the most dynamic instrument on the planet.  When I work on TV and movies, I’m always amazed at how suddenly the voice changes dynamics.  Looking at the waveforms, the T, C, D, B and other consonant sounds are so short and quiet while the vowel sounds are exponentially louder and longer.  This can be a problem when mixing music because you might miss out on an initial or ultimate consonant sound that totally changes the meaning of a song without that consonant.  I remember working on a Christian rock album and the line was “We know that we can’t live with out you.”  When the mixing was done, they loved the track, but the “t” in “can’t” had disappeared.  Of course in a religious context you don’t want to be saying that you know you can live without God, so we had to spend a little extra time making sure that came across without being overbearing.

Just a crazy little factoid, almost all consonant sounds sound the same no matter who says them.  The majority of the time, you can fly in a t from one person, paste it in, and no one would know the difference.  You really only know from the vowel sounds what somebody sounds like.  Consonants are just air pushing against your lips, teeth, tongue, and mouth and we are all roughly equal to each other in body composition—at least enough that it isn’t imminently audible in most instances.

This is also the range where attack sounds live:  picks strumming strings, sticks striking cymbals, this is the range where you can hear all that.  Giving a boost to those sounds in this range can lead to a more present sound.  After all, your mind thinks your closer to something the more detail you can hear of it.  So if you can hear a stick tapping a drumhead, by god you must be close to it.  We’ll talk more about psychoacoustics and proximity in the next article.

Also, many big time producers believe that in this band lies the frequency that makes digital sound abrasive and therefore worse than tape, which centers around 2 KHz.  While this may or may not be the case, it certainly cannot be argued that harshness, edginess, and abrasiveness live in this frequency band.  Raucous and in your face sounds like screeching guitars and sailing synths need this range so that they can cut and make your ear drums bleed.

Next week, I’ll look at some common terms for upper-mid range problems and some common solutions

Honky:  When you cup your hands and sing into it, that is pretty much what honkiness is.  This is a frequency buildup around 500-700 Hz, so cut in that area or boost the lows.

Nasal:  Like when you pinch your nose and speak.  This is very similar to honky except that it is a bit higher around 800-1000 Hz.

Radio-Filter:  The most overused pop cliché out there.  I wish everyone would stop doing this, but to do it properly you should know:  Old radios had small speakers which meant poor bass response and sometimes weak highs as well.  They also had poor construction which means limited dynamic range.  So use high and low pass filters centered around 1 KHz.  Most of the effect will be accomplished by the high-pass filter.  The low pass filter can be adjusted to taste.  Compress heavily to limit dynamic range.

Tinny:  Sounds like it’s coming through a tin can.  To me this also indicates peaky mids which would be a significant bump at around 1 KHz.  Perhaps some high-end reverberations of a metallic variety.  Can be remedied by boosting lows.