ACOUSTICS 101 // FOR GEEKS ONLY

Dear Friends, THIS ARTICLE IS FOR GEEKS ONLY! It's a tad rambling and gets fairly technical regarding a discussion of what defines good "sound quality" in our digital world. So if that's something you're interested in, read on. If not, please spare yourself and skip down to the band listings immediately! I occasionally get a bemused reaction when one of you from the dance community learns I have a degree in music theory and composition. I guess it's surprising, 'cuz everyone knows you don't need a college degree to play in a band. To be frank, not much of my academic background has ever been too relevant to what I do as a Memory Brother, i.e., playing keyboards and singing. Nevertheless, I'd like to think my six-year stint in college might not have been a complete waste; as I spent a good deal of time there writing and producing music in the University of Iowa's Electronic Music Studio. That studio training definitely paid off in another area of my musical endeavors - my role as a recording engineer and music producer at Bird-On-Fire Recording Studio.   Doug asleep at 3 AM in Electronic Music Studio at the University of Iowa (1973.) PREFACE TO AUDIO DISCUSSION I built Bird-On-Fire Recording Studio (with the help of Kevin Conner, Robert Traeger Jr., and Mike Heins) back in 1980 with the sole intention of just recording my own material. But almost immediately I got drawn into recording outside artists and bands. So throughout the past 40 years, I've recorded hundreds of sessions and have been instrumental in the careers of several, successful musicians. A couple of Bird-On-Fire alumni that you might be familiar with would be Emily West (click.) and Nikki Anders (click.) I continued working with aspiring bands and fledgling artists such as Nikki and Emily up until about ten years ago when I decided to go back to just producing my own (Memory Brothers) music. So around 2010 I closed down my main studio but kept my smaller, project studio active for personal projects. And I do still occasionally record a solo artist if they twist my arm sufficiently. Why am I telling you all this? Because I want to establish some credibility regarding my technical background which dovetails nicely into the following, little essay on sound quality which was prompted by a recent email I received. FOR GEEKS ONLY A friend emailed me the following question a couple days ago: "Is 5.1 surround sound the best quality?" I always get a bit excited when someone asks me a question about a subject that I may actually know something about. I'm no good when it comes to changing my car's oil filter or understanding how to do my income tax . . . but when it comes to music and/or acoustics, I enjoy sharing with others what little knowledge I might have. So as I was writing a reply to my friend's question, I got to thinking, "Out of 4,000+ subscribers, I know there's gotta be one or two or maybe even three geeks out there who might also find this discussion of sound quality interesting!" Therefore I've decided to share my reply in this week's newsletter. 5.1 SURROUND SOUND First of all my friend had asked about "5.1 surround sound."  5.1 surround sound really doesn't have anything to do with sound quality per se. It actually refers to a specific type of speaker configuration. In the case of 5.1, we're talking about six speakers - one to the listener's left and one to the listener's right for the stereo signal; one in the middle (center channel) for dialog; two behind and on either side of the listener for special effects (explosions, etc.) and one, big ol' subwoofer for the low frequencies that can be placed virtually anywhere in the listening room. There's also 2.1 and 7.1 channel systems. But again, those numbers simply refer to the number of speakers involved - not the actual sound quality. THE BORING STUFF (PROCEED AT YOUR OWN PERIL) In today's world of digital music, sound quality is dependent on essentially two things: Sampling rate and bit depth of the recorded signal. Human hearing theoretically extends from 20 cycles per second (Hertz) to 20,000 Hertz (that's lowest audible pitch to highest audible pitch.) Think of a waveform on a graph - it cycles ABOVE the centerline and BELOW the centerline for one complete cycle or 1 Hz.  Figure 1. Above graph shows ONE cycle (1 Hz) In order to record a single waveform, you have to "sample" the two parts of the waveform - the part ABOVE the centerline and the part BELOW the centerline. Since the highest frequency humans can hear is 20,000 Hertz, then you'd have to sample 20,000 cycles - each having two parts, the ABOVE and the BELOW centerline portions. So that's a total of 40,000 samples. So the standard CD sample rate is 44,100 Hertz (abbreviated as 44.1 kHz.) For a technical explanation as to why the sampling rate is 44.1 kHz instead of simply 40 kHz, click here As far as bitrate, a very simplified explanation would be: bitrate is the number of divisions of volume steps between the softest and loudest portions of a sound wave. The higher the bit depth (bitrate) the greater divisions between the softest and the loudest portions of the sound wave. So a bitrate of 8 bits would have 256 levels; a bitrate of 16 bits would have 65,536 levels and 24 bits would have 16,777,216 discrete volume levels between softest to loudest. So, what we've been talking about so far has been DIGITAL AUDIO - and of course DIGITIZED audio is audio that has been sampled as discrete "bits" or as little "stair steps" which I refer to in Figure 2 (below.) In the real world, sound waves do not consist of discrete, little "steps;" rather they're continuous, smooth curves (see Fig 1.) Those curves are referred to as "analog" waves. So what we're trying to do in the digital realm is to get as close in "smoothness" to the targeted analog wave form as possible. And as you can see below, as the bitrate increases for the digital waveform, the "smoother" the digital curve becomes (see Fig 2,)   Figure 2. The above four examples show a very low bitrate (A) progressing to a higher bitrate (D.) Notice how the jagged, stair-step waveform approaches the analog waveform (smooth curve) as the bitrate increases.  So bottom line - the higher the bitrate, the more-accurate the representation of the intended, analog waveform. Theoretically, if you could have an infinitely-high bitrate, you would then have an analog waveform. As mentioned earlier, the standard for CD quality sound is 44.1 kHz (sampling rate) and 16-bit (bit depth.) The MP3s you listen to on your smartphones and computers have a much lower quality (sample rate & bit depth) than an audio CD. Also the music you listen to on your Sirius XM satellite service or AM radio is of lower quality than CDs due to the low sample and bit rates needed to accommodate streaming and broadcast standards. There can be higher sampling rates and bitrates than the CD standard of 44.1 kHz and 16-bit, but it's debatable as to whether people can actually discern an increase in quality over the CD standard, i.e. not many people can hear frequencies above 20,000 Hz nor discern the difference between a 16 or 24-bit waveform. WHAT THE AUDIOPHILES CONTEND Audiophile snobs will contend that they can discern the difference between different digital standards. And of course, they'll always contend that vinyl (analog) is the best - until they find themselves confronted with the prospect of double-blind testing. With digital audio there does seem to be a limit at which we humans can no longer appreciate an increase in sampling and bit rates. But the debate rages on among hii-fi enthusiasts. IN CONCLUSION If you've plowed through this article and are still awake, congrats! You may now consider yourself an official "Audio Geek!" And you undoubtedly want to learn more about this subject, so here's an introductory YouTube explanation of sample rate and bit depth that you may find enlightening: click There will be a quiz later.   Doug Koempel | Memory Brothers Thursday, September 5, 2019