Improving Sound in Your Auditorium
By: Dana Jensen
What’s the biggest problem encountered in auditorium acoustics? In one word: understanding. That is, can the entire audience hear clearly and completely what is being said? Parents attend programs to hear their kids, yet the sound can be so muddled and the vocal quality so poor that it sounds like the speaker has a bucket over his or her head.
Loudness isn’t the problem; you can have loud sound but still not hear clearly what is said. The problem is that the listener can hear sound; it is just garbled and unintelligible. You may have experienced this once or twice before.
School auditoriums are notorious for having poor-quality sound. The sound-system operator finds it nearly impossible to get loudspeakers to produce clear and intelligible speech in a challenging venue, such as many auditoriums. It leaves people straining to hear clearly and makes for a poor experience for the audience. This problem is so common that we have become used to it.
Intelligibility and Acoustics: Understanding Is Everything
For music applications, distortions are easily tolerated by the brain, and much contemporary music uses distortion as part of its sound effects. But for vocal requirements, good fidelity is critical. To be understandable, it must be free from distortions or else the brain has difficulty correctly hearing words. This aspect of audio is referred to as “speech intelligibility.” You may be used to vocals that sound “muddy” and are difficult to listen to. If sound is not clear, your audience will be unhappy.
Even audio professionals sometimes find it difficult to get loudspeakers to produce clear and intelligible speech in a challenging venue. What causes poor quality sound? There are a few common factors that affect how a loudspeaker performs in an auditorium context. In many cases, it is due partly to the challenging acoustic characteristics of an auditorium and partly due to the performance characteristics and inefficiencies of the loudspeaker. Concrete floors and walls are horrible for sound quality. Or, you might have an oddly shaped hall. Frequency distortions from loudspeakers contribute to muddy or unintelligible speech of varying quality across a venue. Older auditoriums were not acoustically designed to handle today’s sound requirements. All of these issues interact with each other and contribute to poor audio quality and intelligibility loss.
Consequently, schools are often stuck with various acoustic challenges and have limited options to make improvements that fit their budgets. You may have tried new speakers or equipment, only to find that the same problems remain. Due to physical limitations of cone speakers, a typical 2-way loudspeaker not only contributes to but exacerbates these house problems, and replacing cone speakers with newer cone speakers does nothing to help the problems. Many loudspeakers are not designed specifically with vocals in mind and have poor quality in the vocal range.
The Bad News: Three Top Sound Killers
The first is “muddy voice” problems. When people speak on a microphone, you hear a muffled sound. This comes from properties of a 2-way loudspeaker. The 2-way loudspeaker has been the standard choice for most audiovisual applications, as they are great for producing loud sounds, even though many are not designed for the vocal range.
Why is this so? Let’s take a look at a typical design for a 2-way loudspeaker: a 15-inch subwoofer and a horn tweeter. The tweeter is designed for high frequencies above about 1500hz, and a 15-inch subwoofer is designed for frequencies below approximately 150hz, so they sound great on the high and low frequencies, but poor in the middle range. Unfortunately, the middle is right where the range of the human voice is.
As you have probably experienced, this produces a very “bassy” or muddy-sounding voice. Clarity and intelligibility suffers, fatiguing listeners who strain to hear clearly. We’re asking a subwoofer to give us clarity of sound that is above its designed range. To get an idea of what it sounds like, unplug the main speakers from your home entertainment system and try to get full sound from only the subwoofer. It’s simply not going to produce clear sound in the vocal range. It will sound heavy on the bass—that’s what it was designed to do. As a result, you cannot get a clear-sounding vocal response out of your loudspeakers.
The second common loudspeaker problem is uneven distribution of sound, or “beaming.” A cone speaker produces a narrow beam of sound that does not fill a venue evenly. You may have dead zones where it is difficult to hear or you could experience the problem of blasting the audience in front of the speakers in order to get sound to the back of the room.
Beaming produces frequency distortions similar to the way laptop monitors have visual distortions. You have seen flat-screen monitors where you tilt the screen or look at it from an angle; the colors are distorted to the point where you can barely make out images. The pixels project colors perfectly when you are directly in front of (“on axis” to) the screen. However, the pixels are not capable of projecting the full color spectrum at an angle. Loss of greater parts of the visible spectrum occurs when viewing the display from an angle, resulting in a distorted image when viewing off axis.
The same distortion happens to audio speakers. When you move from the front to the sides of a loudspeaker, some of the audio signal is lost. Bass frequencies are still heard, but the higher frequencies drop off in volume as you move away from direct center. Listeners directly in front of a loudspeaker will hear the entire frequency range, while listeners towards the sides will hear less and less of the full range of frequencies. Loss of the upper portions of the frequency range creates more muddiness and a varied sound quality across a venue. Again, you have loss of intelligibility of speech and listeners straining to hear clearly, not something you want in a school program.
Beaming is simply a function of cone speaker physics. The only way sound technicians can correct this is to set up more loudspeakers and angle them in different directions. Modern speaker designs such as line arrays use more than 20 internal speakers in order to design around this fundamental problem.
The third common source of audio problems is the acoustic characteristics of the room itself. Auditoriums are well-known for echoes and reverberations. An echo is a reflection of sound, arriving at the listener after the direct sound. Reverberation keeps sound bouncing around the room, sometimes for three or four seconds.
Again, for speech clarity, reverberations can make it difficult to understand. If the reverberation time from one syllable overlaps the next syllable, it makes it difficult to identify words.
To sum up, room acoustics and the physical limitations of speakers both contribute to poor audio quality. People spend thousands of dollars on new sound systems and speakers only to find out the same problems still exist. They try all sorts of different microphones and spend thousands on processing equipment and are still not happy with their sound and still cannot understand the words being spoken. The problems remain because they have not dealt with the fundamental problems: room acoustics and loudspeaker deficiencies. These are the issues that sound engineers have gone to great lengths to design around, and they are very difficult to effectively control—up until now.
The Good News: A Solution
Flat-panel technology is so new you may not have heard of it yet. It is the result of the past 20 years of research and development to solve these common audio problems: a flat speaker about a quarter-inch thick and the size of a poster. There are numerous benefits that overcome the physical limitations of cone speakers and their resultant quality issues.
First of all, flat-panels produce exceptionally high clarity and speech intelligibility. It produces crystal-clear sound across the entire vocal frequency range, where clarity is most important. No more muddy voice—people will no longer need to strain to clearly hear the program.
As opposed to the narrow beam of typical loudspeakers, flat-panels have a nearly 180-degree sound dispersion pattern. Therefore, they fill a room with sound in a way not possible with the narrow beam of conventional speakers. Flat-panel speakers put even sound across a venue, eliminating dead zones typically created by conventional speakers. Due to the wide dispersion angle, a flat-panel does not have the same loss of frequencies as the listening angle changes and consequently produces a much clearer sound evenly across a venue. Every listener in the audience will hear the audio, no matter where they sit in the venue—even at the edges and corners of the room where sound is often poorest.
For reverberation problems—even in the most “audio-challenged” venues—a flat-panel will substantially reduce the noise from reverberations.
The flat-panel’s light weight of only 8 pounds makes set-up, take-down, and portability a breeze. Also, you can attach graphics to display artwork, photos, information, or a welcome screen, without degrading audio quality. You could put school logos, event information, or even advertisements on it. With the ability to attach graphics, your technology disappears from view.
As energy usage is a growing concern, flat-panel technology uses a fraction of the power of a typical loudspeaker. You can easily use a low-power amplifier, 80 watts maximum, and get full sound.
The clear sound in the vocal range and the ability to decorate a flat-panel with graphics makes it a good choice for audiovisual applications, education settings, halls and auditoriums—anywhere high clarity sound and visual appeal are required.
The school board will love the price, too, as it can be substantially cheaper than hiring a sound engineer and purchasing sound treatments or lots of new equipment. Another benefit is you can use relatively smaller and inexpensive equipment with flat-panels and still have good sound.
The end result is people in your audience will hear the program clearly, and they will not have to strain to understand. Hearing vocals clearly is a critical issue in auditoriums, as vocal requirements make up most of the use.
Muddy voice and other acoustic problems are too common; don’t give up on getting high-quality audio, even if you have tried other solutions that did not work. Flat-panel technology is now available to you for the first time at affordable prices. It may be the perfect solution for you. Flat-panel technology can make your most audio-challenged venue sound superb.
Dana Jensen is a former electrical engineer, has a degree from Denver Seminary, and now helps give beautiful sound to venues with challenging acoustic problems.
Product Roundup
Anchorage Acoustical Wall Panel from Acoustical Solutions
Anchorage Acoustical Wall Panels are the perfect choice for versatility in your school’s multipurpose room. Available in 36 colors, Anchorage panels are enhanced to provide designer quality that blends seamlessly into existing décors and designs. If you’re looking for acoustical treatment that doesn’t visually disrupt your space, these are the panels you’ve been waiting for. The Anchorage Wall Panels are available in custom and standard sizes and offer acoustic performance from an industry leader in acoustical treatment.
www.AcousticalSolutions.com
Sound Panel from Innovative Sound Solution
The SoundPanel is a thin, lightweight loudspeaker that delivers exceptionally clear sound in a unique flat-panel design. With the ability to attach graphics and a minimal profile, the SoundPanel looks like a poster or work of art hanging on the wall. The SoundPanel eliminates dead zones associated with conventional speakers. The SoundPanel can significantly improve the audio performance of even your most audio-challenged venue. For auditoriums that were not designed for modern sound requirements, the SoundPanel is a brilliant solution for today’s acoustic challenges.
www.InnovativeSoundSolution.com
PZtronics VLA-2 Vertical Array Speaker
PZtronics has released its new VLA-2 vertical line array. Weighing only 20 pounds, these 1,000-watt RMS columns have outstanding resistance to feedback so they are great in permanent installations such as auditoriums. Long projection provides more consistent listening levels to all parts of the room, while delivering high speech intelligibility and natural-sounding music in even the most acoustically demanding spaces. This type of vertical line array provides wide horizontal and narrow vertical pattern control, eliminating ceiling reflections, and therefore improving the acoustical quality of the room.
www.pztronics.com
Tectum Fabri-Tough II Wall Panels
Fabri-Tough II Wall Panels are the latest innovative wall panel introduced by Tectum. Combining abuse-resistant Tectum Wall Panels and a 1/8 inch, 18 pound density fiberglass facer laminated to the face of the panel with new designer fabrics, Fabri-Tough II is perfect for offices, conference rooms, and any space where designer fabrics are required. Control noise efficiently, economically, and attractively in open plan, closed, or mixed-use space with the Fabri-Tough II Wall Panel System.
www.tectum.com
Acoustical Resources
Acoustical Resources has announced the introduction of its custom acoustical art portfolio. Acoustical Resources currently is working on a variety portfolio of acoustical art panels that combine functional acoustics, yet provide visual excitement to any space. The “Celtic Cross” is fabricated from impact-resistant fiberglass core (2 1/8-inch thickness). This piece measures 30 inches wide by 40 inches high, and all materials are Class A fire rated and have an acoustical NRC rating of 1.0. Panel sizing can be scaled upwards.
www.acousticalresources.com
Panelfold
EchoSorb acoustical panels by Panelfold provide superior sound control by deadening sound “bounce” within a room. Perfect for music rooms, auditoriums, theaters, and large halls, these panels can be wall mounted or suspended from ceilings. With custom sizes and dozens of fabrics and colors to choose from, the choices are almost limitless. You can even create panels with your own artwork for a unique design touch.
www.panelfold.com
