Dynamic Range in Radio, Audio and Life
What is it?
In this article, I have gone to some pains to make what could be to some a boring and deep topic at least a little more understandable and less boring to most people.
When to beginning broadcasters it SEEMS like we’re a little TOO nit-picky running good "levels" in the studio, this discussion will hopefully add some insight and some verification that there is actually some wisdom behind our pre-occupation.
At one time, not even a teenager yet, I wondered why songs coming out of a home stereo never sounded quite the same (or as good) as they sounded on the radio. As I would soon discover, radio stations limit their dynamic range before feeding it into their transmitter. It is done for several reasons which will be outlined momentarily, but for whatever reasons, it actually made the music SEEM to sound better. The transients that might otherwise be distorted anyway, were squashed. The bass that might otherwise interfere with clarity were controlled, the characteristics of the drum sounds and air talent voices
were modified in such a way that made them seem more powerful. What was that mystique? It was AUDIO compression
As humans, we all prefer our day-to-day activities to proceed as smoothly as possible, with as little conflict or obstacles as possible. When we travel, we prefer our flights leave as scheduled, our connecting flights synch up as scheduled and our hotel room to be ready when we arrive. When we go to a restaurant, we don’t want to get into an accident on the way, for a table to be available when we arrive, our server to greet us and bring our food on a timely basis and for it to be of reasonable quality. Hopefully they will accept our payment without incident that seems fair and reasonable for what was received.
We want our lives to progress in a constant flow with no rough edges, sort of like the waveform of a standard FM broadcast. What happens within that restricted range of modulation is within the realm of "acceptable."? (For the non-techies the waveform
looks like a straight pipe with a bunch of "squiggies" inside). That’s probably what we would truly prefer, but it doesn’t always work that way.
This is because life itself could probably be described as analog. We’re not bits and bytes, and life may be more like the waveform of a standard AM broadcast. We each live in our own little module of existence that constantly changes. We interact, create more of us, or "things" or thoughts or modify the things around us.
As analog creatures, we also create analog sounds, which for various reasons, we deem to be valuable enough to transport, modify, save or distribute. The accurate transmission of those sounds so as to maximize the effectiveness of the listening experience is at the core of what this article is about. It could also be why we can actually be emotionally affected by the way a radio station SOUNDS. That is if that sound is close to or even resembles what our idea of great sound is. Maybe the content is part of that reaction as well.
In terms of sound, dynamic range is the difference between the softest sounds and the loudest sounds.
WHY IT’S A GOOD THING IN BROADCASTING
In broadcasting, it is necessary to limit the dynamic range to make it easier to listen to in a typical listening environment, to stay legal, have a "presence" on the dial and be competitive. If someone is punching across the dial and yours is significantly lower in volume than the competition, you will not be the station where they stop. In a casual setting, this boils down to audio levels that are consistent.
Back in the studio, someone who is just learning the fundamentals of broadcasting is told to make sure levels never exceed a certain point on the metering, but always averages ABOVE a certain level. When the song ends, the voice should not "blast" the metering into "the red." This would be uncomfortable to listen to, aside from the fact it is considered "unprofessional."
Historically, in the earliest days of broadcasting going back to the 1920s, there was actually an engineer who sat in master control at a radio station whose primarily job was to "ride gain" and make sure the transmitter was not over-modulated. Using his best guess, his job was to ANTICIPATE what was coming next and be ready to compensate for that modulation peak that potentially, could actually damage the transmitter.
Various devices were developed in later decades that automatically took care of that and eliminated the job of just "riding gain." At least for this function, such equipment could actually react much faster than a human. Most of these devices, however, do work (and sound) much better if they are fed what’s known as a "good level." Digital processing is even more forgiving (as long as one doesn’t get to close to their absolute peak), but the garbage-in garbage-out mentality is still a good one: If it sounds bad going in, it will sound equally bad coming out.
In a practical Production environment, the on-air grade of processing is not used nor is it even desired. In other words, get the basics down first. Don’t rely on technology to fix carelessness or sloppy board work!
As already noted, in the Production studio, consistency of levels is, in fact, the key. In the music industry, not only consistency, but balance (both tonal and mixture of vocal and instruments) AND overall loudness (at the final mastering stage) becomes a factor.
A "limited" dynamic range boils down to the quietest sounds are made louder, and the loudest sounds are made quieter. There are various reasons as to why this could be called a good thing in certain applications. Listening environment is a factor.
When driving a car, natural road noise means when listening, you would have to crank up your radio during quiet passages. Except you may have noticed that you DON’T have to when listening to radio because radio stations limit their dynamic range – at least the popular music stations. A classical or jazz or public radio station will probably be more conservative with their processing. With certain musical applications, limiting dynamic range is considered a very bad thing. There can easily be too much of a so-called good thing. Music can lose its impact when over-processed.
HOW LIMITED DYNAMIC RANGE INCREASE STATION COVERAGE
On the plus side, in the analog world of AM broadcasting, a station will have greater effective coverage with a higher average modulation level. This is because as the distance from the transmitter increases, so does the noise. A station with higher (i.e. LOUDER) modulation will be more listenable at greater distances because the listener will not have to turn the volume up on their receiver as high as on a poorly modulated station. When listening to a weaker AM station, when a listener has to turn the volume up, they also turn the volume up on BACKGROUND noise that is inherent to standard analog AM broadcasting.
The general public is not tolerant of a noisy, scratchy listening experience, and you won’t find many people listening to shortwave radio or distant AM stations these days. But maintaining higher average modulation is still a consideration for lower power broadcasters operating on the AM band today.
COMPACT DISC CHARACTERISTICS & "NORMALIZING"
Digital audio on a standard Compact Disc typically has a dynamic range of 100 decibels. A standard analog VU meter is not even half that range. A typical cassette or reel tape recorded above that range would be distorted, or be really hissy if recorded below that range.
With the widespread use of home-burned CDs, often there is not much consideration paid to dynamic range and it is often determined by whatever level the source recording was made when it was first transferred to a digital format.
Consumer-oriented CD burning software has made some effort to help the average person make their CD’s sound A LITTLE more like commercially produced CDs. They have a process called NORMALIZING.
Normalizing is a method that does NOT reduce the dynamic range. It merely moves it to a different (usually higher) level. It is also not audio compression in the sense that we think of it.
What it does is find the highest peak in a song and increases THAT peak to a pre-set level determined by the user (often as a percentage). Whatever the percentage of increase is, the entire song will be increased by that same amount. For example, if that peak was at 80% and you Normalized it to 95%, a 15% increase would be applied across the board. Thus, a segment of audio that peaked at 50% would then be increased to 65%.
Depending on the source of audio, the recording would only change in overall volume. It would NOT sound more "punchy." For that characteristic sound, you need true audio compression as well as a modification of tonal balance. Unless it was an air check from a broadcast station that was already compressed in this way, by "Normalizing" one would merely get a louder CD, but it may not seem PERCEPTIVELY louder, because the overall average level was not changed. Only the peaks were raised.
Today, software is readily available that can modify an existing sound recording in such a way that it can closely approximate what the most advanced processors are capable of.
Modification of the actual dynamic range is a standard attribute, but the methods of modification so as to introduce little or no undesirable artifacts (or to introduce DESIRABLE artifacts) are the coolest facets that evoke an emotional response.
AUDIO PROCESSING ARTIFACTS ACTUALLY CREATED THE SOUND OF AN ERA
In the 1960s and 1970s, "pumpy" "vacuum cleaner" sound and even reverb recall nostalgic feelings of the songs that were popular at that time. Those of us who worked on-air at that time won’t soon forget how "BIG" our voices were made to sound on the headphones (and suffer from considerable hearing loss today). By the time multi-band processing became common place (and it became more common for separate processors to become part of the chain for microphones only), technology found a way for talent to sound "BIG" and full, without that constant sucking sound.
Dynamic range was being restricted in all cases. Newer technology, lower noise gear and source audio along with better-designed studios allow us to modify the dynamic range so it was less obvious. Yet the end result is clearly apparent: When I punch up a station in town that CLEARLY stands out with a very round, full, yet crystalline characteristic, and as the programming transitions and the sound never degrades, I know that there MAY BE a certain brand of processor in use, perhaps with a certain pre-set appropriate for the format designed by the manufacturer. Then I go to Station B and it still sounds good, but in comparison, very flat and lifeless, I would tend to return to Station A, even if the programming content was less desirable.
Restricting dynamic range and manipulating audio to function as an end product, is in fact, an art form and there are many different stages of artistry. Running good levels in the air studio is only one aspect of building the "painting" of a radio station.
THE SOUND OF THE STATION STARTS IN THE RECORDING STUDIO
That sound actually starts in the RECORDING studio, the very first time that artist uses his voice or plays his instrument while it is still in its purest analog form. There is but one chance to capture it properly at that stage and as needed, mix it properly with other instruments, and balance the dynamic range. In fact, the earliest engineers were referred to "Balance Engineers."
If a station sounds great… full of "punch", "guts", "pristine," "crisp without sounding harsh," or whatever words you want to use describe, it’s due to any combination of things including a good engineer at the station, good equipment, and good control or manipulation of the dynamic range and tonal balance from the very first time it was first recorded.
A voice-over recording in a Production studio certainly falls into that category but so does the rest of the programming content.
If the "snap" of the bass drum in a popular music song recorded 30-40 years ago can be heard clearly over THE RADIO today, there is no doubt that the recording engineer who sat patiently in that studio, who set up a certain microphone a certain way, as well as the MAINTENANCE engineer who painstakingly aligned the recording machine – ALL played a role in how that radio station can have that sound at that moment.
Basically, the Balance Engineer operated the equipment of the era within the specifications of its manufacturer, insuring that it was within its dynamic range capabilities. Throughout the process of that piece of audio traveling from then to now, people or equipment followed the rules of maintaining good consistent levels all without introducing undesirable ARTIFACTS (there’s that word again).
If at any point along the journey, the raw analog waveform were seriously clipped or otherwise grossly damaged in such a way that is audible, that station would not sound as good at that moment.
Audio restoration is also an art form in itself, but restored audio that has been seriously damaged can never come close to audio that has remained pristine from the microphone to the speakers in the car.
For further insight…
Giants among us in the recording industry include Roger Nichols, Grammy award winner for his technical achievements. He is also responsible for the sound of every Steely Dan song you’ve ever heard and countless other artists you’ve heard on the radio. He currently also teaches an audio mastering class, and creates custom plug-ins for Pro Tools… www.rogernichols.com
On the British side, Geoff Emerick, whose work at EMI (Abbey Road studios) gave the Beatles their legendary sound that rivals any studio recording made today wrote a book a couple years ago. "Here There and Everywhere" gives tremendous insight into what he did to achieve great sound when technology was so primitive. Another related book that gets back to basics: "All You Need is Ears," by Sir George Martin.