Last Updated: November 2019
It can be deceptively easy to mix and master a track, but what happens to the sound when it leaves the speakers?
Our friends at Get That Pro Sound give a rundown on sound design techniques that will seduce your listeners’ ears into hearing exactly what you want.
Sound Design Tricks 101
With using mere basic knowledge about psychoacoustic principles, you can find creative ways to bring your listeners a more powerful, clear, and ‘larger than life’ experience. By understanding how the hearing system interprets sounds, we can creatively and artificially recreate certain responses to particular audio phenomena, particularly EQ, compression and reverb.
For example, if you incorporate the natural reflex of the ear into the designed dynamics of the original sound by including a very loud hit, the brain will perceive the sound as “loud” (even when it’s played back relatively quietly).
You’ve fooled the brain into thinking that the ear has closed down slightly in response to ‘loudness’. The result? The experience of loudness is quite distinct from actual physical loudness.
1. The Haas Effect
Named after Dr. Helmut Haas (who first described it in 1949), this principle can be used to create an illusion of spacious stereo width…starting with just a single mono source.
Haas was studying how ears interpreted the relationship between originating sounds and their ‘early reflections’ within a space. His conclusion was that – as long as early reflections and identical copies of original sounds are heard less than 35ms after (and at a level no greater than 10dB louder than the original) – the two sounds will be interpreted as a single one.
The directivity of the original sound would be essentially preserved, but because of the subtle phase difference, the early reflections/delayed copy would add extra spatial presence to the perceived sound.
The Haas Effect in Practice
In a musical context, for thickening and/or spreading out distorted guitars (or any other mono sound source), it’s a good trick to duplicate the part, pan the original to extreme right/left, and pan the copy to the opposite extreme.
You might also delay the copy by between about 10-35ms (every application desires a slightly different amount) by shifting the part back on the DAW timeline or inserting a basic delay plugin on the copy channel with the appropriate delay time dialed in. This tricks the brain into perceiving larger width and space while leaving the center wide open for other instruments.
You can also use this technique to pan a mono signal away from the busy center in order to avoid masking from other instruments. At the same time, you don’t want to unbalance the mix by only panning to one side or the other. The answer lies in “Haasing it up” and panning your mono signal both ways.
Consider Using Slight Delays
Of course, there’s nothing stopping you from slightly delaying one side of a real stereo sound. For example, you might want to spread your ethereal synth pad to epic proportions. Just be aware, however, that you’ll also be making it that much more ‘unfocused’ as well. For pads and background guitars though, this is often entirely appropriate.
As you play with the delay time setting, you’ll notice that too-short delays result in a pretty nasty out-of-phase sound. Meanwhile, too-long delays will break the illusion, and you’ll start to hear two distinct and separate sounds. You’re looking for something in between, which will sound just right and help you catch the space you want.
Find the Right Balance
Remember: The shorter the delay time, the more susceptible the sound is to unwanted comb filtering when the channels are summed to mono. This is something to consider if you’re making music primarily for clubs, radio, or other mono playback environments.
You’ll also probably want to tweak the levels of each side (relative to each other) to maintain the right balance in the mix and the desired general left-right balance within the stereo spectrum.
You can apply additional effects to one/both sides, like applying subtle LFO-controlled modulation or filter effects to the delayed side.
A word of caution: Don’t overdo it. In a full mix, use the Haas Effect on one or two instruments, maximum. This helps you avoid unfocusing the stereo spread and being left with phasey mush.
2. Frequency Theory: How Masking Works
There are limits to how well our ears can differentiate between sounds that occupy similar frequencies of human hearing.
Masking occurs when two or more sounds sit in the exact same frequencies. Generally, the louder of the two will either partially or completely obscure the other, which then seems to ‘disappear’ from the mix.
Obviously, this is a pretty undesirable ‘phenomenon,’ and it’s one of the main things to be aware of throughout the whole writing, recording, and mixing process. It’s also one of the main reasons EQ was developed, which can be used to carve away masking frequencies during the mixing stage.
Our audio trick? Avoid masking problems during the writing and arranging stages by using notes and instruments that occupy their own frequency ranges.
Even if you’ve taken precautions, masking will still sometimes occur at the mix, and it’s difficult to determine why certain elements sound different solo than they do in the full mix.
Although the root notes/dominant frequencies of the sound have the space they need, the sound harmonics (that also contribute to the overall timbre) appear at different frequencies. These may still be masked, which is a point where EQ might come to the rescue.
3. The Ear’s Acoustic Reflex
As mentioned in the introduction, when confronted with a high-intensity stimulus, he middle ear muscles involuntarily contract. This decreases the amount of vibrational energy that transfers to the sensitive cochlea, which converts sonic vibrations into electrical impulses for processing by the brain. Basically, the muscles close to protect the more sensitive structures of the ear.
The brain interprets the dynamic signature of these reduced-loudness sounds, with the initial loud transient followed by immediate reduction when the ear muscles respond. The result? It still senses ‘loud sustained noise’.
This principle is often used in cinematic sound design techniques and is particularly useful for simulating the physiological impact of massive explosions and high-intensity gunfire (without inducing hearing-damage lawsuits).
The ears’ reflex to loud sounds can be simulated by manually playing with fine dynamics of sound. You can make that explosion appear quite loud by artificially shutting down the sound following the initial transient. The brain will immediately perceive it as louder and more intense than the sound actually is. This also works well for booms, impacts, and even drops in a club or electronic track.
4. Create Power and Loudness – Even at Low Listening Levels
If you take only one thing away from this article, hear this: The ears’ natural frequency response is non-linear. More specifically, our ears are more sensitive to mid-range sounds than frequencies at the extreme high and low ends of the spectrum. We generally don’t notice this, as we’ve always heard sound this way and our brains take the mid-range bias into account. It does, however, become more apparent during mixing, where relative levels of instruments (at different frequencies) change depending on the overall volume you’re listening at.
Even though your own ears are an obstacle to achieving a perfect mix, there are simple workarounds to this phenomenon. You can also manipulate the ears’ non-linear response to different frequencies and volumes in order to create an enhanced impression of loudness and punch in a mix – even when the actual listening level is low.
The Fletcher-Munson Phenomenon
This nonlinear hearing phenomenon was first written about in 1933 by researchers Harvey Fletcher and Wilden A. Munson and although the data and graphs they produced have since been improved upon, they were close enough that ‘Fletcher-Munson’ is still used as a shorthand phrase for everything related to ‘equal loudness contours’.
Generally, you should be able to do the best balancing at low volumes (this also saves your ears from unnecessary fatigue). Loud volumes are generally poor for creating an accurate balance because, as per Fletcher-Munson, everything seems closer than it is.
Think About Your Audience
In certain situations (like mixing sound for films), it’s better to mix at the same level and similar environment to where the film will eventually be heard.
This is why film dubbing theaters look like actual cinemas and are designed to essentially sound like them too.
The best mixes result from taking the end listener and their environment into account, not necessarily mixing something that only sounds great in a $1 million studio.
So, how do our ears’ sensitivity to the mid-range manifest on a practical level? Try playing back any piece of music at a low level. Now gradually turn it up: As the level increases, you might notice that the ‘mid-boost’ bias of your hearing system has less of an effect, with the high- and low-frequency sounds seeming proportionally louder (and closer, which we’ll go into in the next tip).
Given that extremely high and low frequencies stand out more when we listen to loud sound effects, we can create the impression of loudness at lower listening levels by attenuating the mid-range and/or boosting the high/low ends of the spectrum. On a graphic EQ, it would look like a smiley face, which is why producers talk about ‘scooping the mid-range’ to add weight and power to a mix.
How to Apply This Audio Trick
This trick can be applied in any number of ways, from treating the whole mix to some (careful) broad EQ at mixdown/mastering to applying a ‘scoop’ to just one or two broadband instruments or mix stems (i.e. the drums and guitars submix). As you gain experience and get your head around this principle (you might even already be doing it naturally), you can build your track arrangements and choices of instrumentation with an overall frequency dynamic – right from the beginning.
This is especially effective for styles like Drum & Bass, where amazingly impactful and rich-sounding mixes – with just a few elements that really work those high and (especially) low ends. The mid-range leveling can then act primarily as an indicator of a ‘nominal’ base level, made artificially low to enhance the emphasis on the massive bass and cut high-end percussion and distortion.
The same works well for rock too: Just listen to Butch Vig’s production on Nirvana’s “Nevermind” for a classic example of scooped mids dynamics.
Remember to be subtle: It’s easy to overdo any kind of broad frequency adjustments across a whole mix. If in doubt, leave it for mastering.
5. Equal Loudness Part II: Fletcher-Munson Strikes Back
Of course, the inverse of the closer/louder effect on the ears’ nonlinear response is also true, and equally useful for mixing purposes. To make things appear further away – instead of boosting – roll off the extreme highs and lows. This creates a sense of front-to-back depth in a mix, pushing certain supporting instruments into the imaginary distance and keeping the foreground clear for the lead elements.
This (and the previous trick) works because of how our ears interpret distance from a sound source by the amount of high- and low-frequency energy present (which is relative to broader mid-range content).
Our ears have adapted to take basic physics of our gaseous Earth atmosphere into account: beyond very short distances the further any sound travels, the more high-frequency energy (and extreme low-end to a slightly lesser extent) will dissipate as it travels through the atmosphere.
Put These Sound Design Techniques into Action
To push a sound further back in the mix, try rolling off varying amounts of higher frequencies and hear it recede behind the other elements. This is particularly useful for highlighting a lead vocal in front of a host of backing vocals (cut the BVs above around 10kHz, possibly boost the lead vocal in the same range). It’s also a solid choice for EQing drum submixes to ensure the drums are punchy overall but not too in-your-face. A touch of reverb is also an option here, naturally.
6. Transients Appear Quieter Than Sustained Sounds
The human ear doesn’t perceive short duration sounds as loud (or long) when they’re at exactly the same level. This is referred to as RMS or ‘Root Mean Square’ response, a mathematical means of determining average signal levels. This is the key auditory principle behind how compression makes things sound louder and more exciting without actually increasing the peak level.
Compressors aren’t as intuitively responsive as the human ear, but they’re designed to respond in a similar way. Compressing the tails of sounds tricks the brain into thinking sound (like a drum hit) is significantly louder and punchier. But the peak level – the transient – has not changed. This is how compressors allow you to squeeze every ounce of available headroom out of your sounds and mix. Just be careful not to ‘flatline’ your mix with over-compression.
7. Reverb Early Reflection ‘Ambience’ For Thicker Sounds
If you combine part of the Haas Effect principle with our previous tip on sustained sounds, you’ll already understand how adding early reflections from a reverb plugin can attractively thicken sounds.
Here, we’re using it to essentially multiply and spread the initial transient attack portion of sound over a very short amount of time. By extending this louder part of the sound, we’ll get a slightly ‘thicker’ sound, but in a very natural, ambient way that’s easily sculpted and tonally fine-tuned with various reverb controls. With the distancing and diffusion effects of the long tail, you can retain the ‘upfront’ character of the sound.
8. Decouple a Sound from Its Source
A sound as it is produced and perceived in a final context is really not the same thing at all.
This principle is liberally exploited in movie sound effects design, where the best sound designers are able to completely dissociate the sonic qualities and possibilities of a sound from its original source. This is how Oscar-winning Ben Burtt came up with the iconic Star Wars lightsaber sound:
“I had a broken wire on one of my microphones, which had been set down next to a television set and the mic picked up a buzz, a sputter, from the picture tube – just the kind of thing a sound engineer would normally label a mistake. But sometimes bad sound can be your friend. I recorded that buzz from the picture tube and combined it with the hum [from an old movie projector], and the blend became the basis for all the lightsabers.”
– Ben Burtt, in the excellent The Sounds Of Star Wars interactive book
The Start of Techno
The Roland TR-808 and TB-303 were originally designed to simulate real drums and real bass for solo musicians. The results were pretty shocking as they did sound like real instruments, but trailbreaking Techno producers like Juan Atkins and Kevin Saunderson perceived their potential to be more exciting than backing up a solo guitarist at a pub gig.
By misusing and highlighting what made them unique from the real thing, these pioneers turned loud bass into screaming acid resonance and tweaked the 808 kick drum to accentuate
its now signature ‘boom’.
Johnny Cash’s Signature Sound
Consider Johnny Cash’s infamous track “I Walk The Line”, which featured his technique of slipping a piece of paper between the strings of his guitar to create his own ‘snare drum’ effect. Apparently, Cash did this because snares weren’t used in country music at the time, but he loved their sound and wanted to incorporate it. Coupled with the train-track rhythm and the imagery of trains and travel in the lyrics added a new dimension to the song – just one of the magical moments of studio recording.
The Ends Really Can Justify the Means
Whether you’re creating a film sound effect or mixing a rock band, you don’t have to settle for the raw or typical instrument sounds you started with. If you find that kitchen pans give you sounds that fit your track better than an expensive tuned drum kit, use them! If you discover pitched elephant screams are the perfect addition to your cut-up Dubstep bassline (it works for Skrillex), by all means, herd them in.
The only thing that matters is the perceived end result: No one’s ears care how you got there. They’ll be subliminally much more excited and engaged by sounds coming from an unusual source, even if said sounds take the place of a conventional instrument.
9. Sound Design: How to Make a Mix Sound Fuller
Our ears can have trouble deciphering where one sound ends and another similar one begins, but they’re incredibly forgiving when it comes to layered sounds. When done carefully – even across wide ranges of the frequency spectrum – the separate components will ‘read’ as one big, textured sound.
This is basically how musical chords work, as well as a major principle behind expensive and lush Hollywood-style sound design. This is also true for complex, ‘How did they do that?’ effects in electronic music.
The Practical Art Of Motion Picture Sound discusses creating layered sound effects as though there were chords. A single effect is made up of several individual sounds/‘notes’ which occupy their own frequency range (this is key to avoid simply masking one sound with another). Adding your own timbre or dynamics all together provides a depth, texture, and power that’s simply not possible with a single-source sound, no matter how much it’s processed.
Use this technique to layer whole stacks of guitar or synth parts into towering walls of sound that can then also be spread across the stereo field with the Haas Effect. Build signature drum kits by layering frequency and timbral elements from multiple sources to create the ultimate Tech House kick or Dubstep snare drum. The possibilities for tricking our ears are endless!