Posts Tagged blockaid

Demystifying Acoustic Data: Part 1 – Absorption vs Isolation

For anyone new to the world of acoustics, there is a multitude of terms, coefficients and numbers that are thrown around.  This flood of information can seem intimidating, especially to beginners. In this series, acoustician Cameron Girard of Acoustics First® hopes to help you distinguish between what’s useful and what’s not.

NRCvsSTC

Part 1: Acoustic Terminology – Sound Absorption vs Sound Isolation

In order to make informed decisions about acoustical treatment, it is vital to know the difference between materials that are meant to absorb sound within a room and materials that are meant to block sound from leaving or entering it. In an overly reverberant auditorium, absorptive treatment is needed to reduce echoes and improve speech intelligibility. If the problem is sound passing in between spaces, like offices or apartments, then isolation treatment is required. These are two separate acoustic issues which require separate solutions.

In both scenarios, it is important to know which data is relevant and helpful. Also, given sheer volume of information available on the internet, it is perhaps unavoidable that some info will be incomplete or simply incorrect.  It should not be assumed that something which sounds technical is, in fact, backed up by proper testing.

Terms for Sound Absorption

We recently encountered an acoustical ceiling tile which was said to “absorb 50% of sound”. On the surface this sounds like an extremely efficient product.  However, let’s delve in closer and decipher what is actually usable information, and what is just marketing.

When sound waves meet a room surface such as a wall, ceiling or floor, some of the sound energy is reflected back into the room and the rest is considered to be “absorbed”.  The absorbed sound energy has not vanished, it’s actually been converted into kinetic (vibration of a solid material) and thermal energy (heat due to friction within a porous material) or has simply passed right through the material (transmission). The more surface area a certain material has the better absorber it will likely be. “Soft” materials, like heavy blankets, fabric and fiberglass, have loads of nooks and crannies, which sound tries to “fill”. These porous materials are great for reducing reverberation within a room, but will only marginally reduce the sound that leaves it (but more on that later).

Sonora® wall and ceiling panels are used for absorbing sound within a space.

Sonora® wall and ceiling panels are used for absorbing sound within a space.

When comparing sound absorbing products, there is a particular set of terms you should look for: The Sound Absorption Coefficient (SAC) and Noise Reduction Coefficient (NRC). These are used to specify the fraction of incident sound that a material absorbs per 1’x1’ area. An NRC of 1.0 indicates perfect absorption (an open 1’x1’ window) and a value of 0.0 represents perfect reflection (polished concrete has an NRC of .02).

To measure sound absorption, a large sample of the material is placed in a reverberation room with all other surfaces being hard and reflective. The time it takes a test sound signal to decay by 60dB (rough point of inaudibility) after the source of sound is stopped is measured first with the sample in the room and again with the room empty. The difference in decay time defines the efficiency of the absorbing material and thus the absorption coefficients.  Large spaces with low-NRC materials (tile, drywall, etc.) have longer reverberation times, while small rooms furnished with high-NRC materials sound much more “dead”.

Clearly, a single 2’x2’ ceiling tile is not going to reduce the reverberation in a real-world space by 50%. So is the above claim false? Not exactly… The ceiling panels do have an NRC rating of .50, so the tile does absorb 50% of incident sound. However, one might assume a much more drastic improvement based on the “50%” claim. In reality you’d need a large square footage of these ceiling tiles to cut the amount of total reflected sound in half. Always be sure to check the NRC number!

Terms for Sound Isolation

Our customers often call with issues related to neighbor noise or office-to-office privacy and are looking for “sound proofing” treatment. Unfortunately, many do not realize that simply installing acoustic foam or fiberglass panels will not appreciably reduce the level noise entering and leaving their space. These absorptive materials are great at reducing unwanted reflections within a room because they are porous and air/sound energy can flow through them. That being said, they are generally poor sound barriers for this exact reason.  They will help to reduce noise buildup in a room and improve the ‘acoustics’, but will do very little to “block” sound coming in or out.

BlockAid® is a heavy impermeable barrier for stopping the transmission of sound.

BlockAid® is a heavy, impermeable barrier for stopping the transmission of sound.

Sound is like water; it will “flow” into an adjacent space if everything isn’t sealed up. Materials that are air tight and heavy, like our BlockAid® sound barrier, provide the most relief of air-born sound transmission. Continuous coverage of floors/ceilings or walls is necessary to ensure that sound doesn’t ‘flank’ around these barriers. Multiple layers of varying materials, the use of resilient clips or channels, and additional walls will provide even more control.  For a demonstration of how different materials affect sound isolation, check out our video http://acousticsfirst.com/educational-videos-the-barrier-and-the-bell.htm

Like NRC for sound absorption, there is also a laboratory tested figure that can be used to compare the sound “blocking” properties of acoustic barriers and wall constructions: Transmission Loss (TL) and Sound Transmission Class (STC). These describe how much air-born sound is attenuated through a given material.

In the lab, the material to be tested is mounted over an opening between two completely separated rooms, one with a speaker (source) and the other with a microphone (receiver). Save for the open “window”, these rooms are completely isolated with thick and massive walls, so virtually all the sound energy transmitted between rooms will be through the test specimen. The difference between sound levels in the source room and the receiving room is the transmission loss (TL). The TL is measured at multiple frequencies, which is fitted to a Sound Transmission Class (STC) “curve” at speech frequencies (125Hz-4kHz). The STC of the material is the TL value of the fitted curve at 500 Hz. For example, a material with an STC of 27 typically “blocks” 27dB of sound. Keep in mind though, the STC’s of materials do not add up linearly; in other words, adding a material with an STC of 27 to an existing wall with an STC 45 will not result in an STC of 72.

As always, Acoustics First is here answer questions and help you find the best solutions.

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DIY – Treating a Wall – BlockAid® and SoundChannels®

AcousticsFirstOn many occasions, we get asked about common ways to treat a wall (or walls) either for broadcast, podcast, or other voice recording scenario – where they not only want to tame the reflections within the room, but also block a certain amount of sound coming into – or leaving the room.

Budget is frequently an issue, major construction is usually unwanted, but effective results are always required.

We’re going to show you how to handle a room upgrade – cut down on the sound transmission and cut the room reflections – all with the same skills required to hang high quality wall coverings!  Let’s see how you can cover a wall with BlockAid® vinyl sound barrier to block unwanted sound, then go back and cover that with an absorptive layer of Sound Channels® wall covering  to finish it off!

This treatment is not recommended for renters, as this is not an easy upgrade to undo.  However, if you have an extra bedroom you are using as Podcast studio, this is a great way to treat it… Let’s get started!

Installing BlockAid®

Measure the wall for the first panel length. Mark the panel width on the wall.

1. Measure the wall for the first panel length. Mark the panel width on the wall.

Measure and Mark the length of the wall on the BlockAid®

2. Measure and Mark the length of the wall on the BlockAid®

Use a straightedge and a razor to cut the BlockAid® to length.

3. Use a straightedge and a razor to cut the BlockAid®.

Using a trowel, apply vinyl tread adhesive to the wall, covering the whole area where the first panel is going. (You marked the wall right?)

4. Using a trowel, apply vinyl tread adhesive to the wall, covering the whole area where the first panel is going. (You marked the wall right?)

Hang the panel starting at the top, install a few screws to hold it in place while the adhesive sets. (You will probably need a friend to help, as BlockAid® is a pound per square foot!)

5. Hang the panel starting at the top, install a few screws to hold it in place while the adhesive sets. (You will probably need a friend to help, as BlockAid® is a pound per square foot!)

Using your hands and a putty knife, smooth out all the air bubbles from behind the BLockaid® so that you get a good bond when the adhesive cures.

6. Using your hands and a putty knife, smooth out all the air bubbles from behind the BlockAid® so that you get a good bond when the adhesive cures.

Repeat the steps for the next strip. Measure, Mark, Cut, Trowl, Hang...

7. Repeat the steps for the next strip. Measure, Mark, Cut, Trowl, Hang…

Make sure you line up those seams! push them right up agaist each other. Smooth out the air bubbles, cut out any outles, trim any extra... Let dry!

8. Make sure you line up those seams! push them right up agaist each other. Smooth out the air bubbles, cut out any outles, trim any extra… Let dry!

Good job! Now, take a breather while that dries, and notice how much less sound is passing through the walls.  This is when you will notice that the sounds are now coming from under the door, and through the leaky old window.  These can be taken care of in different ways…. but the easiest way is the same way you deal with keeping the cold out!   Get some weather strip, a door skirt, seal the gaps around the frame of the door, and windows, maybe go out and buy some heavy curtains for the windows… if you have some leftover BlockAid®, you can always get some Industrial Velcro and temporarily stick a piece over the window!

Installing Sound Channels®

1. Remove the Screws from the BLockAid® - if you didn't already... then same as BlockAid®, measure the wall, mark it, measure and cut a piece of Sound Channels® and start troweling on the Chapco!

1. Remove the Screws from the BLockAid® – if you didn’t already… then same as BlockAid®, measure the wall, mark it, measure and cut a piece of Sound Channels® and start troweling on the Chapco!

2. Well, when you get tired, make your friend finish troweling out the adhesive to cover where the panel is going. (You are going to overlap the seams.)

2. Well, when you get tired, make your friend finish troweling out the adhesive to cover where the panel is going. (You are going to overlap the seams.)

3. Starting at the top, hang the Sound Channels® overlapping the seam of the BlockAid under it. Smooth out the air bubbles with your hands. Make sure it lines up well. No screws needed!

3. Starting at the top, hang the Sound Channels® overlapping the seam of the BlockAid® under it. Smooth out the air bubbles with your hands. Make sure it lines up well. No screws needed!

4. Measure and cut the next strip, carefully following a rib in the fabric, while your friend, (who is way better at troweling than you are anyway,) preps the next section with adhesive.

4. Measure and cut the next strip, carefully following a rib in the fabric, while your friend, (who is way better at troweling than you are anyway,) preps the next section with adhesive.

5. Best practice is to run the fabric in the same direction every time. Not just with the ribs, but in the same direction it comes off the roll. So find the top.

5. Best practice is to run the fabric in the same direction every time. Not just with the ribs, but in the same direction it comes off the roll. So find the top.

6. After you find the top, start hanging from the top, lining up the seams and smoothing out the bubbles as you go.

6. After you find the top, start hanging from the top, lining up the seams and smoothing out the bubbles as you go.

7. Keep those seams tight as you go. Keep smoothing... almost done!

7. Keep those seams tight as you go. Keep smoothing… almost done!

8. Trim up the extra and repeat as many times as needed.

8. Trim up the extra and repeat as many times as needed.

That’s it!

Don't forget to trim around those outlets!

Don’t forget to trim around those outlets!

This treatment is a common first step in treating many professional broadcast studios – it gives you extra isolation with the barrier and takes the edge of the sound reflections.  Many professional environments then go back and add some additional treatments such as bass traps, diffusers, and broadband absorber panels – especially if these studios are planning on bringing in any musical guests.

This isn’t just for home studios.  It works great for kids play rooms, bedrooms, home theaters, home gyms, and any place you want to block sound and tame the sound inside the room.

Customize your space as you will, but this treatment is a consistent winner for cost and performance, and is a great way to get started without breaking the bank!

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Season’s Greetings!

Acoustics First would like to wish everyone a happy holiday season, and a happy new year.

Seasons Greetings from Acoustics First

– Acoustics First Team

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DIY: Fix Music Stand Ringing and Reflection

DIY Project – Music/Copy Stand Cover

Take a few seconds and DIY fix some of the common problems with using metal music stands!

DIY-covered music standNot too many people think about their music stands, but we all have them somewhere.  Usually it’s one of those you see to the right – the great, sturdy, utilitarian devices that they are.  Unfortunately, there are a couple inherent problems with these:

  • Ringing – The metal resonates causing a ringing effect.
  • Reflections – many times you are using a stand close to a microphone and getting early reflections off the stand.

Here’s a few DIY fixes for these common problems.

  • a few feet of composite foam will give you both reflection and ringing fixes

The ultimate suggestion would be the Composite Foam/Barrier adhered directly to the stand, then covered with Sound Channels® fabric – This would turn your stand into a mini absorber.

Do the front and back! Make a slip cover for a temporary/removable solution.

This simple DIY project is provided as a way for our customers to learn better ways to use our products and get more value out of the products they buy.  If you are looking for more ways to use the products you have, look to Acoustics First for Ideas.  http://www.acousticsfirst.com

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Acoustics First Corporation supplies acoustical panels and soundproofing materials to control sound and eliminate noise in commercial, residential, government, and institutional applications worldwide.  Products include the patented Art Diffusor®, sound absorbers, noise barriers, acoustical fabrics and accessories. Acoustics First® products are sold for O.E.M applications, direct, and through dealers.  For more information on acoustical materials and their application, please visit www.AcousticsFirst.com or call Toll Free 1-888-765-2900 (US & Canada).

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Setting the Stage for Acoustics First

Setting the Stage for Acoustics First

Setting the Stage for Acoustics First
by Nick Colleran

Originally Published in Productions Magazine Sept/Oct 2012 issue.

Early acoustical theaters were just that – acoustic. The good news and the bad news are usually the same news when a venue sounds incredibly good at the start. An auditorium that projects natural sound well is most often over-powered and overloaded by modern musical performances and the line array sound systems that reinforce them. That’s the bad news in the good news. This type of good room will need to be modified to handle high-powered sound from modern music performances while keeping its sound-enhancing properties. All efforts can be directed into the “how” of doing the job when everyone has heard the “why” it needs to be done.

Re-engineering reinforcement – Modifications for “loud”
The hard back wall of the stage is a significant source for monitor splash-back into the performers’ microphones, reducing gain-before-feedback and enhancing opportunities for system squeals. This is in addition to promoting timing confusion due to slap-back that is usually out of sync with the music. This disturbance and annoyance can be overcome by using materials from the province of industrial noise control. A factory finish, that is a finish for the factory, is also both “roadie-proof” and “on-the-road” compatible. Yes, you can take it with you. This allows one set of materials to follow the performances from one venue to the next.

Curtain call – Reflecting on the stage
The industrial curtains called QFM for Quilted Fiberglass Materials accomplish multiple functions:
Bass control from an internal limp mass, Absorption from quilted fiberglass, and Resistance to abuse from a tough vinyl cover.

The covering is thin enough to avoid reduced effectiveness at all but the highest frequencies and strong enough to withstand stage and road wear. Hanging mass (at one time plywood) with an absorptive cover is a long-standing studio technique to control low frequencies. The newer, non-rigid barriers allow a curtain configuration that is invisible to the audience, while providing a clean sound source for the both the performers and the listeners.

Overhead, not overheard – Many are baffled
Above the stage, there is almost always a large cavity designed for lights and to accommodate rigging. This space can act as an unintended echo chamber. Being out of harms way, the area allows for a lighter and less costly sound treatment with acoustical baffles. Besides the obvious requirement that they work acoustically, they need only to be invisible (usually black) and pass the proper fire code. Acoustically, they have about twice the exposed sound absorbing surface as a wall-mounted panel, by hanging in free space. It’s more surface, less reverberation, out-of-sight and within budget. They are light enough and small enough to travel well if strung in a way that allows easy removal for relocation, such as threaded onto aircraft cable and hung in a line from side-to-side. Adding a fabric finish to the baffles, produces a more decorative product, suitable to the audience side of the auditorium when a more permanent ceiling solution is required.

Stage One – Separating Sound
Stage one of acoustical control often is the stage. Both on-stage and in-studio sound isolation usually begin with structure borne sound traveling through the floor. It is always wise to implement isolation between instruments from the beginning, where it is a “cheap” fix rather a costly solution. This can be accomplished by floating the stage surface, and doing it in several separate sections. As noted previously with the hanging back of stage curtains, mass matters. Mass can come from many different materials whose properties are heavy and dense. They can be common materials such as gypsum or sand as well as more acoustically specific items like sheet lead or mass loaded vinyl barrier. (BlockAid® is a readily available example.) Added mass damps the damage of vibration and reduces ringing resonance.

Once the stage goes “thud” when hit due to its added mass rather than a cartoonish “boing”, it is time to handle the hollow space beneath the stage and fill it with fluffy stuff. This can be whatever attic insulation that is on sale at the local home improvement store. It need only trap the air to prevent its becoming a big bass drum when stomped upon.

Way back in the days of Disco (or Disco daze), complications arose in the studio from the required “lead-foot” kick drum getting into the acoustical piano by traveling through the studio floor as vibration and transmitted up the piano legs. Although studio floors are usually isolated from other rooms, they can still connect within a room. This problem was solved by floating the drum booth independent of the common recording studio floor. At that time this author’s studio went so far as to construct a sand-filled floor set on nine truck tires. The sand provided mass and inertia while the tires created de-coupling from the common structure. Today it is accomplished with high mass materials and off-the-shelf vibration pads, at about the same cost. Independent and transportable compact structures can be created for the individual instruments and be moved with very little heavy lifting.

After stage resonance is reduced by adding a layer of mass loaded vinyl to its surface and the cavity below is stuffed with fiberglass to prevent its ringing or singing along with the music, a second stage may be layered on top of the original and floated on ribbed neoprene pads every 12 inches along standard, 16” on-center bracing. This keeps the guitar amp’s sound out of the vocal microphone stand, bass drum out of the piano legs, and so on, to create increased clarity and improved separation in the live performance.

Islands in the stage will stop transmission transit and are relatively cheap to build into the plan. Separate sections for drums, piano, singer, bassist and guitar amplifier can be buffered with half-inch strips of flexible resilient neoprene without being seen. Much like vocals can be modulated when source through the same speaker as the bass, surfing the bass wave in the stage floor can also add an undesirable tremolo (or vibrato) effect to voice or other wind instrument. (This effect can be demonstrated by auditioning a vocal through the bass player’s amplifier while playing.)

Dome details – Round and around
One technique used in early acoustical performance theaters was the overhead dome. This feature captured wasted sound energy and focused it back to the audience to reinforce sonic energy in areas where it had diminished with distance from the source. With new systems the level is electronically reinforced, not needing further enhancement, which confuses rather than clarifies. In addition, the dome creates a sonic racetrack where the sound moves around the edge in a swirling motion. Anyone who has been in a domed facility during a thunderstorm has heard how sound travels around the perimeter. The RCA dome in Indianapolis provided a good example to CEDIA attendees a few years ago . This phenomenon of raceway runaway can be abated with acoustical “speed bumps” of Melamine foam which easily bends to conform to curves*, keeping the look while truncating the travel of the fast moving sound waves. In this case being unfocused is a desirable trait.

To reduce sound getting into the dome from the line arrays and the like, hanging baffles can be placed around the front half of the perimeter of the ellipse. These may be fabric covered to blend with the décor of the audience area and made from two-inch, seven pound per cubic foot density acoustical fiberglass to extend its absorption range. Being hanging baffles they do not permanently change the original architecture, where that is a concern.

(Don’t Look) Behind the curtain – Unseen, Unheard
When acoustical treatments must be essentially permanent, high efficiency at low cost can be achieved with utility finishes that can be field-cut to fit spaces in cavities behind auditorium side curtains. Factory fit panels require precise measurements to install within curves. Field cutting skips this step as it is, by definition being, done in real time to as-built measurements rather than made to out-of-date plans. Savings derived from the unseen, utilitarian treatments can be applied to upscale finishes for panels in plain sight.

Balcony bounce-back
Another common problem for an older theater in the modern world is sound returning from the balcony face. These are usually concave surfaces that not only send sound back but focus it for feedback as well. Convex curves such as polycylindrical “barrel shapes or semi-reflective half-round, hollow traps can control concave characteristics when interspersed with thicker, flat acoustical wall panels to achieve a combined “Flat” curve.

Definition by Diffusion
Sound intensity can be reduced by the decision to destroy or diffuse. Absorption is the destructive choice, eliminating the problem by eliminating the sound. Care needs to be taken to use only what is necessary and no more.

The other alternative is to spread the sound over a larger area to reduce intensity. This can be likened to spreading peanut butter on bread – it becomes easier to swallow although it is the same quantity as the original lump from the jar. With diffusion, a little goes long way. A single barrel shaped diffuser can clear up the cacophony of a board room without the deadness of absorption required for the same amount sound clarification.

Check back After Launch
With venue retrofits, some tweaks can be made after opening. Covering all walls before there is an evaluation with performers and audience, is not always a good idea. While it may be theoretically possible to model and predict acoustical performance, it can be more economical and efficient to get the room in a reasonable range and polish to the real world result. An informed conclusion, upon hearing the room in use, can produce an optimum result.

*Contrary to popular belief, acoustical foam can be painted to match décor without affecting its performance. (The author has a copy of the independent lab report comparing painted to unpainted natural. Painted measured better, but not significantly.)


The Author 

Nick Colleran is past-president of SPARS (Society of Professional Audio Recording Services), past president of the VPSA (Virginia Productions Services Association), a former recording artist and audio engineer.  

Starting in 1978, his company began supplying unique acoustical materials. Nick now leads a “quiet life” as a principal of Acoustics First Corporation.  The company holds patents for several innovative acoustical products.

Acoustics First designs, manufactures and distributes products to control sound and eliminate noise for commercial, residential and industrial uses.

Materials Mentioned:

Vib-X™ vibration pads | BlockAid® mass loaded vinyl noise barrier | Stratiquilt™ quilted industrial blankets | Cloudscape® Baffles hanging acoustical baffles | Sonora® acoustical wall and ceiling panels | Select Sound™ black fiberglass board | Geometrix™ half-round broadband absorbers

Download of article available here: http://acousticsfirst.com/article-setting-the-stage-for-acoustics-first-productions-mag.htm

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Acoustics First Corporation supplies acoustical panels and soundproofing materials to control sound and eliminate noise in commercial, residential, government, and institutional applications worldwide.  Products include the patented Art Diffusor®, sound absorbers, noise barriers, acoustical fabrics and accessories. Acoustics First® products are sold for O.E.M applications, direct, and through dealers.  For more information on acoustical materials and their application, please visit www.AcousticsFirst.com or call Toll Free 1-888-765-2900 (US & Canada).

 

Originally published by Home Toys.

http://www.hometoys.com/emagazine/2012/10/setting-the-soundstage-how-to-treat-your-home-theater-like-a-real-theater/1977

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