Psychoacoustics (the study of how the brain perceives sound) is an insanely complicated field that many spend years studying. But you don’t have years, so to help answer the question “what is music?”, why we dig it, and why it sounds the way it does blasting through a sound system, we tapped Bose sound engineer Eric Freeman for an assist on why you love Abba so much… maybe a little too much, actually.
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Music is not noise
Why does a piano sound different than, say, the white noise of a TV? It’s largely because they have different frequency spectra. No, that’s not a sci-fi-themed cover band. Frequency refers to the rate of vibrations of a soundwave, where higher frequencies = faster vibrations = higher pitch. In the case of a piano, those frequencies form a repeating pattern, giving it a pleasant pitch. Basic “noise” has a bunch of random frequencies that make for a jagged, random wave. Check out those fancy drawings!
Your ears hear certain frequencies better than others
Humans can theoretically hear frequencies in the 20–20,000 Hz range (or from a real low organ note to a super-high tin whistle). That range is divided up into smaller segments called critical bands, some of which are naturally more sensitive in the human ear than others. For example, bassy sounds aren’t very noticeable, while high mids and trebles (like pop vocals) come across more clearly. Another example: a crying baby occupies our ear’s most sensitive range. It’s nature’s little trick to make sure we hear an infant in need. Nature didn’t consider 14-hour flights sitting next to one of those infants that isn’t yours, though.
Instruments are very specific
A sound’s spectrum helps to tell us what the sound is. That piano wave you saw up there? That set of vibrating frequencies is specific to only the piano and no other instrument. The human voice, for another example, has a very complex sound spectrum, mainly because of the breadth of different pitches and sounds involved. Sound systems like the ones from Bose are set to make those vocal frequency ranges natural and clear so that lyrics or speech stand out.
If the sound isn’t natural, we can totally tell
Ever wonder why electronic music sounds like robots on trampolines? Well, all those iconic synthesizers started out in the early 1950s as a computer’s attempt to create an instrument, which was limited by the amount of data that a computer could store. Natural instruments, on the other hand, have rich timbres. So, the first computer-made sounds had much simpler soundwaves, and our ear could totally tell. Sure, computers are now much more capable of synthesizing realistic timbres, but those early synth sounds are now so synonymous with electronic music that they’re still used for aesthetic reasons. Peep those waves up there to see how they’re different.
The material used for speakers has a big effect
Those black circles inside your speakers? Those are called cones, and their job isn’t to serve you rum raisin, it’s to play your music. Cones do this by vibrating rapidly based on the electronic signals they receive (from the music files you’re playing). They in turn push and vibrate the air, which is what your ears hear. While metal cones often support high frequencies, paper cones are much more versatile. Bose uses mostly paper cones because their main goal is to achieve super natural sound. Stay tuned for more on that later… get it? Tuned.
Cones and transducers have very specific purposes
Driving those cones are transducers, which are essentially electromagnets that take that aforementioned audio signal (bumpin’ tunes) and translate that to your earholes. Bass soundwaves naturally pour out of speakers in all directions, while higher sounds are much more focused (think of dumping a bucket of water vs. spraying a hose). Ergo, higher-frequency cones are placed facing where a listener is likely to be, while lower-frequency cone placement doesn’t matter as much. It's why people often tuck a sub woofer off to the side or into a corner of their living room sound system.
The speaker’s house pumps things up
But what about the box that all that stuff goes in? The way an enclosure is constructed has a huge impact on the quality of the sound. Often, physical compartments are built into speakers (called ports, seen in that pic up there), and these compartments take air produced by the speaker cones and amplify it to generate louder or lower frequency vibrations. This essentially adds depth and volume (read: a ton of bass from that tiny box) to transducers with more limited capabilities. And that’s important, because if you push a transducer past its capabilities, it’ll start to sound distorted.
Sound systems use fancy shmancy digital signal processing
To push sound even further, speakers employ digital signal processing (DSP). Freeman told us that Bose uses a special form of DSP called “dynamic equalization” in their new SoundTouch series to help your music sound as ear-catching as possible. Essentially, it adjusts the system’s equalization shape (the prevalence of its highs, mids, and/or lows) depending on the volume of the music. For example, since bass frequencies are less apparent to the human ear, when music is very quiet you might not even hear the bass under all those rich mids and highs. Dynamic EQ will automatically boost that bass at lower volumes to keep things sounding right. And that’s just one trick; Bose was notably tightlipped about their other DSP secrets.
Bose EQs are designed to sound as life-like as possible
For Bose, “natural, and life-like” is the name of the sound game. No need to overdo the bass on a delicate folk tune, ya know? The goal: make things sound crisp and clear. Freeman points out that the things we’re used to hearing are the ones that are most difficult to present realistically from a speaker, such as speech and acoustic guitars. These sounds are so recognizable to the ear that Bose spends a ton of time making sure they sound just like their real-world counterparts by employing the best equalization shapes, placing cones and transducers correctly, and using the enclosures to support it all. But that also brings us to their crazy speaker testing:
Speakers have been tested ad nauseum
Bose puts their speakers through the absolute ringer. Beyond the usual lab signal testing (using machines and do-dads), they actually have a full crew of employees that test out the speakers with real-world music each time they introduce a new line. These test tunes range from classical, heavy metal, and pop to podcast-style chat sessions to crazy “ringer” tracks that are essentially just torturous tones held over long periods of time. Employees are even encouraged to use their own playlists to get the legit experience. What has your workday playlist done for you lately?
Speaker placement in your home has a huge bearing
So where does that fancy SoundTouch speaker go? Suffice it to say where one puts the speaker is almost as important as what’s in it. More bassiness? Place those guys against the wall or in a corner. Clear sound in a crowded room? Make sure the speakers are at ear level! And remember without psychoacoustics, the only jam you’d be loving is boysenberry.