The Nyquist theory says that if we can sample the top of a waveform and the bottom of the same waveform, we can extrapolate the trajectory in between and fill in the missing parts.
This is one reason why standardized 44.1 kHz CD encoding was accepted, albeit not without a fight, as it yielded a top-end frequency response of over 20 kHz. Plenty of response to satisfy our typical human maximum of 20 kHz hearing, even if quantization was used to fill in the gaps, especially at high frequencies.
But consider this: a splash cymbal can create overtones in the 30 kHz range or higher. Can we hear that directly? Not unless you’re a dog or a freak of nature, but sound, especially musical sound, is highly predicated on the interdependence between frequencies, even ones that are “out of band” of normal hearing.
Intermodulation distortion is an example of this interdependence. So is spatiality. So is a good mix. What we call “CD quality” is generally perceived as the best mainstream result for portable digital music, trumped only by more esoteric disc formats like SACD, which by the way sound very good, even to trained ears. But who owns an SACD player?
Not many people. I bet more people have turntables hanging around than SACD players. CD quality is a bit like a one-eyed man being king in a world of blind people - it just seems to be as good as it gets because there isn’t anything better readily available to the masses. From CD quality, digital audio compression algorithms bring us to “near CD quality” and from there it just turns into sonic crap that makes downloading, storing and porting tunes between devices easier.
Compression certainly doesn’t improve audio quality - once content is gone, it’s gone.
Enter the MP3. MP3 is an audio compression standard that somehow got in the door like one of your kid’s bad friends. MP3’s real-world viability is predicated mostly on satisfying a way to get music across networks and onto storage devices while using a minimal amount of space.
But the MP3, even at its highest bit-rate is little more than a thief that stole your music quality. MP3 uses a “loss-y” compression scheme, meaning that bits of information are not just missing due to native encoding practices, but that the loss continues to build as you compress the material to the MP3 format.
This thievery in MP3’s is called “Perceptual Coding” meaning that frequencies beyond our “perceptual ability” are considered less important and can be removed. Would we remove a drum solo from a concert because we didn’t think there were drummers in the room that would notice? No way.
The problem cascades with all the various encoded audio formats that are available; go from CD to MP3 and you lose information and quality.
Take that MP3 and convert it to WMA and you lose even more. The more you change formats through transcoding, whether you’re going to greater or lesser bit-rates, you lose more quality.
Why then do we tolerate a music delivery system that promotes reduction of sound quality in recorded source material, especially when there are coding schemes that are “Iossless” like Free Lossless Audio Codec (FLAC) and Apple Lossless (AlAC)?
These lossless codec examples may not be the be-all of compression encoding, but allowing the herd mentality of a new generation of music lovers - who just want the tunes to download to their computer and onto their iPod before they finish their Rockstar energy drink and go on to playing World Of Warcraft—to drive the accepted paradigm of modem portable digital music quality is insane.
It doesn’t have to be this way and it shouldn’t.
The conversion of music to the bit stream has great empowerment, both appreciative and disruptive. The reach and ease of using the Internet to deliver music is seductive and panders to the power of the network and pop culture. Unfortunately, that pandering brings us squarely up against the current limitations of the modern communications medium, which places a priority on compactness, portability and speed over quality.
Bit-stream-based businesses and manufacturers also want to sell things; music players, music download services and Google-style ads to a young and digitally empowered generation. As storage becomes less expensive and network bandwidth and speed become greater, we can look to a future where we do not need to place limitations on audio quality for network or storage efficiency.
The key is to not lose sight of what quality audio really mean” and prevent a new generation of listeners from believing that the current music download and transport technologies and the limited result they deliver are the only way to go.
As live audio folks who listen to the real thing night after night, venue after venue, let’s teach our children and our understudies well the merits of good sound reproduction. If we don’t, then simple minds will get what is pushed upon them, good or bad.
The modern data world and the culture it engenders generally doesn’t understand or care that stored music must be an honest and accurate representation of the original performance.
Let’s all work to change that mindset.
Steve Olszewski is a musician, soundman, technologist, ex-road dog and black-belt martial artist.