Tag Archive: sound

  1. How Sound Works in Rooms

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    Most rooms have highly-reflective, flat walls, ceilings, and floors, and they can be a lot like echo chambers if left acoustically untreated. If you’ve ever been in an empty apartment or house, you’ll be familiar with the way sound reverberates in empty spaces.

    We know that too much reverberation or echo makes for unsatisfactory acoustic experiences, but without some of it, our brains are equally frustrated in forming accurate sound images.

    Why is Reflected Sound Bad?

    fabric wrapped panel
    Our video and blog, Your Brain On Sound, illustrate how acoustic environments contribute to—or detract from—our brains’ ability to construct accurate sound images. In the same way that binocular vision enables us to perceive depth of field in 3-dimensional space, the separation and orientation of our ears also enables us to accurately locate sound sources in a similar way.

    Reflected sound arrives at our ears later than original, direct sound – even though both started out at the same time. Not only that, but sound travels at about 1,130 feet/second, so in a room about 18long, for example, a sound wave will travel back and forth between the walls about 60 times in 1 second.

    In other words, sound travels so fast, it fills a room almost instantly. And considering the fact that it also propagates in 360 degrees, it’s easy to understand how a room with bare, highly-reflective surfaces will create a nearly infinite number of sound waves all reflecting in infinite directions and colliding and interfering with each other.

    All that reflected sound interferes with direct sound. While it distorts direct sound, it also generates further patterns of destructive interference – all serving to drastically diminish our listening experience.

    How Can We Make Our Rooms Sound Better?

    We can use absorbers to soak up some of the excess energy of reflected sound along with diffusers that help to even-out the sound – resulting in clearer, crisper, more-accurate sound imaging in our minds.

    sound absorbers bouncing off wallsAbsorbers

    As illustrated in our video, How Sound Works (In Rooms), you can use sound absorbers to reduce the strength of the reflected sound energy that would otherwise cause more destructive interference– but not all of it. Too much absorption makes a room sound dull, dead, and unnatural, and, typically, we don’t like overly sound-absorbent rooms.

    We offer many customizable, affordable, and highly effective absorbers. Here are a few for your consideration:

    NOISE S.T.O.P. FABRISORB™ fabric-wrapped wall panels are affordable fiberglass sound absorbers that deliver high performance value at an affordable cost. You can install them on nearly any wall and ceiling surface to reduce echo and reverberation. They come in many color and size combinations and do a great job of taming overly-reflective rooms.

    CFAB Cellulose Sound Absorber Panels are also very cost-effective, offering great performance at a low price. They control and deaden noise and reduce airborne sound transmission. They have a Class A Fire Rating, resist mold growth, and are easy to install.

    Sound Silencer™ acoustical sound panels are also Class A fire rated with both STC and NRC ratings . These panels provide high-performance sound blocking and absorption.

    sound diffusors bouncing off wallCurved Surface Diffusers

    Diffusers reduce the strength of flat-surface sound reflections by spreading out the sound energy, which smooths out and mitigates destructive interference patterns throughout a room. Every room presents unique acoustical challenges, depending on its size, layout, and purpose, but judicious deployment of diffusion is a critical component of any acoustical treatment strategy.

    For a great demonstration of how profoundly an acoustical treatment can impact sound quality, watch our video, How Sound Works (In Rooms).You’ll notice how the acoustically-treated room maintains enough reverberation to “make sense” to our ears and brains. As we illustrate in our blog and video, Your Brain On Sound, the timing/phase of the reflected sound agrees with how and where our brains “expect” to locate the source of sound.

    The CURVE System™ consists of an array of diffusers, absorbers, and corner traps that simplify the creation of professionally-accurate and natural-sounding acoustic spaces. We can help you to determine the best configuration for your work, residential, or home-entertainment rooms.


    The right combination of diffusion and absorption will mitigate and decrease unwanted sound interference – while maintaining suitable ambience and tone. The result is much clearer, more natural, and better overall sound. Your ears and your brain will love it!

    For more information and a wealth of resources, please visit https://www.acousticalsurfaces.com/.

  2. Your Brain on Sound – Understanding the Fundamentals About Sound & Hearing

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    Understanding a few fundamentals about what sound is and how we hear it will help you better understand how acoustics work. Our sense of hearing is a finely-tuned evolutionary adaptation to our environment, one of the critical tools in our survival kit.

    Understanding how sound and hearing are related better enables us to control, shape, and enhance our acoustic environments.

    If a Tree Falls in the Forest, Does it Make a Sound If No One’s There to Hear It?

    Here’s a classic question for you: “if a tree falls in the forest, does it make a sound if no one’s there to hear it?”

    It’s really a philosophical thought experiment at the conjunction of observation, perception, and “knowing” – a.k.a. “cognition.”

    Our senses deliver our brains vast arrays of information. After sorting through the raw data of our touch, taste, smell, sight, and hearing, complex neurological systems generate mental representations of reality.

    This points to an important characteristic of sound: it exists as a mental construction. It’s “all in our heads,” a cognition within the subjective phenomenon of consciousness.

    In other words, if there’s no one there to hear it, one might argue that a tree falling in the woods doesn’t make any sound at all.

    But enough philosophy … let’s have a closer look at what we know about the behavior of sound and how we can shape and control it to enhance our acoustical environments to better our satisfaction and understanding.

    A Few Fundamentals: What is Sound and Hearing?

    audiophile roomWhen matter vibrates, the energy of its vibration exerts pressure on the molecules of the medium it’s in. This energy propagates through media in wave forms that can be measured and that occur in different lengths (frequencies) and amplitudes (degree of power) – all depending on the physical properties of a particular source.

    Sound energy is transmitted through gases, liquids, and solids by exerting pressure on the molecules of those media. That’s why there is no sound in the vacuum of space – there is no medium through which to propagate any energy.

    When sound energy reaches us, the microscopic hairs and delicate bones inside our ears vibrate in response to it, and a complex system of nerve endings transmits that information to our brains which then accomplish the incredible task of interpreting this information to construct a “sound image” in our mind.

    In other words, “sound,” per se, doesn’t exist “out there” – in the world at large – nor does it exist exclusively in the minds of hearing subjects. As far as sound is concerned, all that exists is the presence of kinetic energy emanating from vibrating matter and propagating through some medium in wave forms. It is only after a brain interprets this energy that sound is perceived; i.e. the hearer hears.

    Sound Imaging: Hearing as a Mental Construction and Evolutionary Achievement

    Over countless millennia, our hearing has evolved to such an extent that it forms a critical component in our minds’ ability to construct representations of the world.

    The sound images that our minds generate are as potent, visceral, and central to our safely navigating the world at large as is our ability to interpret the light that enters our eyes and enables us to see it as well – perhaps even more so, because our hearing system never sleeps like our “seeing system” does.

    Our brains and ears are finely-tuned to construct accurate sound images in our minds. Under natural acoustic conditions, our hearing enables us to determine the location or source of sound, its distance, the size of the entity creating the sound, and, most importantly, whether a particular sound represents danger or not.

    Hearing, like all of our other senses, evolved to enhance our survival. When we hear a sound, we almost immediately recognize and generate an “acoustic image” of its source – what, where, how big or small, and whether it represents a threat or not.


    Our ears are highly responsive to short, sharp sounds – twigs snapping or glass shattering. Sound professionals refer to them as “transients.” In the context of evolutionary defense strategies, this makes total sense. We’ve got to know where a sound is coming from if we hope to escape whatever potential danger may exist. Our brains quickly calculate whether immediate danger is imminent or whether there’s no threat at all.

    Our lives could literally depend on it! “Was that the blood curdling roar of a pouncing lion or the plaintive cry of an abandoned kitten?”

    Stereo Hearing: Timing, Loudness, and Tone Differences in 3 Dimensions

    Similar to the way that bifocal vision enables us to perceive three dimensions, having two ears enables us to form sound images that accurately map acoustic environments in three dimensions as well.

    Transients help our brains create a sound image by comparing the differences in timing, loudness, and tone between our two ears.

    When you record using two microphones, you record the differences in timing, loudness, and tone between them, creating the stereophonic effect. Think of how much mileage some of your favorite psychedelic music got out of those sweeping left/right pans that helped listeners feel like they were tripping to the galaxy’s edge and beyond, or at least to the dark side of the moon.

    The stereophonic effect provides an accurate “sound image playback” because it simulates our ears’ physical separation and orientation, and this is central to the way we expect to hear the world. Simply put: it sounds ‘more natural.’

    Big Point #1: Good Room Acoustics Are Essential for Accurate Sound Imaging

    curved wall panelsWe seem to be most “acoustically satisfied” when we hear accurate sound images played back with electronics, speakers, and acoustics that don’t damage or interfere with timing (phase), loudness (amplitude), or tone (harmonics).

    In our video, How Sound Works (In Rooms), we show how flat surface reflections damage timing, loudness, and tone. Using two nerf guns, we demonstrate the difference between direct sound and reflected sound, and we explain how strong reflected sound interferes with our ability to form accurate sound images.

    To reduce excessive reverberation, interference patterns, and distortion, you need to use a combination of sound absorption and diffusion.

    A Fine-Tuned Balance: Absorbers and Diffusers

    piano room acousticsSome acoustical treatments, however, can be problematic because they also damage timing, loudness, and tone – otherwise known as phase, amplitude, and harmonics.


    While some absorption is good, too much of it can kill the sound energy in your room. When you overly-dampen reverberation, it’s harder for your brain to perceive space and location, and it also diminishes pitch perception.

    It kills the room ambience and creates a mis-match between what our brains expect to hear and what we’re actually hearing, and that doesn’t sound natural.


    Diffusers help to spread out reflected sound energy, thereby reducing the potential for strong reflected sound to interfere with direct sound. Since our hearing has evolved as a survival tool, our brains are very sensitive to phase—or timing—for the purposes of sound location.

    Diffusers don’t kill ambience or pitch perception, but there is a problem. Namely, “phase shift diffusers” – like “quadratic residue” designs – work by distorting the timing or phase relationships within the reflections, and that will damage the sound image.

    Big Point #2 – Timing Accuracy Is Essential to Accurate Sound Imaging

    Timing accuracy—phase coherence—is essential for accurately recording and hearing sound imagery. Phase-non-coherent diffusers diminish our brain’s ability to form accurate sound images. In other words, our brains can’t make sense of the sound we’re hearing.

    Phase Coherent Diffusion

    Can we use common sense to improve our sense of hearing? Absolutely.

    “Phase-Coherent Diffusion” is an acoustic treatment that preserves Timing (Phase), Loudness (Amplitude) and Tone Relationships (Harmonics). It’s been around for some time now. RCA in New York, for example, was using this method as early as 1941.

    Phase-coherent diffusers smoothly spread out sound reflection energy, reduce “hot spots,” and allow us to use less absorption. This improves our hearing by retaining a level of ambience that’s agreeable to our ears. It preserves accurate sound imaging and location, and helps us hear crisper, clearer sound overall as well as a more expansive sense of space.


    Our brains are truly amazing. Given the right acoustics, they’re capable of using sound to determine the location, size, and type of a sound almost instantly. Because of the incredible fine-tuning of our hearing, we are sensitive to our acoustic environments. We definitely have the means to significantly improve the sound in our work environments, homes, and recreational spaces.

    Treat your room with Acoustical Surfaces Curve Diffusors. Mounted vertically or horizontally, they are the most natural-sounding, accurate, affordable improvement you can make to room acoustics … and the easiest. They’re phase-coherent, lab-tested, and field-proven.

    For more information and a wealth of resources, please visit https://www.acousticalsurfaces.com/ and/or https://www.acousticgeometry.com/.

  3. The ‘Long View’ of Sound

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    There’s a moment early in the movie “Men In Black” – after a big green alien has raised “all his hands and flippers” (and was then blasted into goo) – where a tired-out Agent D says to Agent K “They’re beautiful, aren’t they?”

    K replies “What?”

    And D says “The stars. We never just – look anymore.”

    NASA hubble telescopea

    Image courtesy of NASA’s Hubble Telescope

    I’m in the sound business, so I don’t worry much about blasting alien creatures into goo – but I can relate to Agent D’s statement, though about sound, not the stars. I tend to lose my “long view” of sound because I’m continually focusing on the technical aspects of a sound, not the beauty of sounds themselves – laughter, a nicely-played acoustic guitar, an espresso machine finishing a cappuccino – these are all intrinsically lovely (especially the coffee machine early in the morning).

    Because my work is listening “critically” to sound, including how a room interacts with that sound, for me, leaning back and just listening – as a simple emotional experience – doesn’t happen as often as it should.

    I’ve found, and you might have, too, that good acoustic environments allow me to more easily lose myself in the long view of sound, to more naturally enjoy my sense of hearing without thinking about it. Few of us contemplate the sonic damage done by lousy acoustical spaces, which separate us from “an enveloping sound experience” – marketing-speak for “simply listening”.  The acoustic signature of the space in which we’re listening, with all the room flaws imposed on the original sound, can easily pull us away from the emotional pleasure of sound itself, even if we don’t know anything about the bad acoustics causing the issue.

    Humans have highly-developed hearing systems which have evolved over millennia to be able to quickly discern danger. Our hearing is especially sensitive to directional information (“which way should I run?”), based on timing differences between our two ears. Because stereo (two-channel) sound depends greatly on timing information between the two stereo speakers to create the illusion of 3-dimensional space (and reality), speakers and acoustics that disrupt our natural ability to accurately hear timing, or “phase”, have a destructive effect on how well we receive emotional cues from sound and music. Closely relating room acoustics and a “long view of sound” might seem like a stretch, but my experience has proven to me that it’s a very important part of fully enjoying sound.

    If you think about something while trying to enjoy it, you’re probably enjoying it less… in bad-sounding rooms, much less. Ultimately, it’s why acoustically-oriented people do what we do – everyone deserves to hear sound clearly, without room problems, as much as possible. To that end, Acoustical Surfaces stays current with scientific and manufacturing technologies, offering acoustical products that will greatly improve the sound of nearly any space. Whether you need to improve the sound of a home theater, a corporate meeting room, or a commercial facility, our sales and support team knows the best products to enable hearing sound clearly. The stars are beautiful, as Agent D said, and so is listening to sound in rooms with good acoustics.

  4. How Does Sound Work?

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    I think that people, in general, have a hard time understanding how sound works. I know it took me a long time, and I still only know the very basics. Maybe it is because it is unseen and unknown? When you are in a room that sounds great, you don’t even think about it. When you are in a room that sounds bad, you definitely notice it and want to do something to fix it. At least that’s how it is for me. Most people don’t even know that they can do anything about it.

    There are some great analogies about sound that helped me out a lot. Very generic, but they helped me to understand. If you are a visual person, like myself, you will really enjoy this video that helped me understand the way sound works in rooms. John Calder from Acoustic Geometry, our sister company, made a wonderful video that explains how sound works in rooms. He uses a Nerf gun to represent the path that sound travels along with some other fun props. I think it is worth a view, even if you already have a grasp on how sound works. It was produced so that even my mom (sorry mom) can understand what is going on.

    click anywhere on video to play/pause