Archive for category HOW TO
Back in April 2021, Acoustics First® Posted a blog about a listening room designed and built by Ken Fritz. This is an overly-simplified statement, as he not only designed and built the structure, but also the massive speakers, the high-tech turntable, and many of the other components. The next month, John Gardner, Nick Colleran, and Jim DeGrandis were invited to witness Ken’s masterpiece of a room in person – and now, a year later, Ken is no longer with us.
Let’s back up a little bit. The history of this room goes back decades, and there is a common history between this room and the Acoustics First® HiPer Panel®. While Ken was finishing the structure back in the early 2000’s, he was focused on building a room that would help his speakers reach their ultimate potential. He had researched the geometry of the finest halls and theaters and their construction, but he was looking to take it one step further. When he was shopping for acoustic treatments for the space, he came across Acoustics First® – which was near his home. At the time, Nick Colleran and John Gardner were working on ideas for a new type of multi-layer, perforated composite, which would eventually become the HiPer Panel®. After the product completed development, and its patent was still pending, Ken’s room became the first installation of the new product.
Ken consulted with Nick and John multiple times during the long construction process, his uncompromising attitude toward his space was always looking for the “best way, no matter what it took.” His bass traps were styled after professional mastering facilities, where the entire corner was recessed and filled with low-frequency absorption. His ceiling was modeled to direct the reflections toward the upper rear of the room, above the balcony. The speakers were hand built, as was his turntable – all of which were marvels of engineering and detail.
I will never forget Ken’s enthusiasm when he indulged in listening to his favorite recording of the “1812 Overture”, complete with Howitzer cannons. The magnitude of the sound would have shaken everything in the room, had Ken not meticulously isolated and anchored everything. The sound was pure and clean, even at 105dB (standing at the rear of the room – and balanced perfectly.)
But Ken wasn’t just about the music or the gear, he also liked to educate and learn. After listening to the recording, he went on to discuss how they had recorded the cannon shots, and even had an audio sample of the different “takes” done during the setup. This was Ken… he wasn’t just interested in how it sounded, but the process of how they got there.
We hope that Ken’s enthusiasm continues to inspire those who have an uncompromising love of music and sound, and that he will be remembered as one of the most fervent proponents of “following your dream.”
Posted by Acoustics First in Absorption, Art Galleries, Articles, Auditorium, Broadcast Facilities, Diffusion, Home Entertainment, Home Theater, HOW TO, Industrial Facilities, Media Room, Multipurpose Rooms, Music Rehearsal Spaces, Offices, Product Applications, Recording Facilities, Studio Control Room, Teleconferencing, Theater on April 29, 2022
For the May 2022 edition of “The Construction Specifier,” Acoustics First was asked to illustrate the use of absorption and diffusion in creating optimal acoustic spaces. The article is a great reference for understanding the types of acoustic absorbers and diffusers, as well as some use scenarios like offices, critical listening spaces, and larger communal spaces.
Note: This version has been edited and the advertisements are removed. The full published version of the May 2022 digital edition can be found on The Construction Specifier’s website here.
Sometimes you just don’t have the wall space for acoustic treatment. When this is the case, you will often see treatments move to the ceiling… but what do you do if you have lower ceilings, or many ceiling fans and fixtures?
This ceiling was sloped toward the massive windows on the outside wall, and it had lights and fans running right up the center. Complicating things further, the opposite wall had sconce lighting, doorways, HVAC, and even more windows. Finally, the floor was not carpeted to facilitate cleaning – as is the norm in many dining spaces.
Direct-mount acoustic panels are a great solution in these scenarios. Here we see an array of 4’x4’x2″ Sonora® panels attached to the ceiling in rows running down the length of the space. While our Tone Tiles® are often selected for their ability to blend in aesthetically, this particular installation proves that Sonora® panels wrapped in fabric are also a solid choice.
Using BlockAid® Clear Vinyl Sound Barrier is a great way to cut down on unwanted neighbor noise, especially during leaf-blowing season. For this installation, clear vinyl panels were fabricated to size, with heavy-duty Velcro stitched right onto the vinyl. The mating Velcro was simply installed around the window, and presto! You have a significant reduction in unwanted leaf-blower noise, while still being able to see out of your window. Now you can sleep in, even when your overly eager leaf-blowing neighbors do not. Clear Vinyl window covers are also great for reducing unwanted noise from lawnmowers, snow-blowers, cars, marching bands, etc.
Your room works as a system with many variables – some of which will affect the performance of your acoustic treatments. However, a laboratory test chamber for absorption is a reverb chamber – and they sound terrible! The test parameters have limits for placement of sources (speakers), microphones, and samples in the room to facilitate a more repeatable measurement. Incidentally, none of these parameters are made to use the material at its highest efficiency – quite the opposite. When you spread the materials around the space, they will perform differently than if you bunch them all together (which incidentally, is exactly how most are tested!) If you place materials at certain positions in a room, relative to the source and listening positions, you will optimize the performance of those materials in the space.
Still, if you are looking to buy some acoustic material (an absorber, sound diffuser, barrier, isolator, etc.), you will likely look into the tested performance of these materials. If you delve deeper into the different test numbers, like Sound Absorption Coefficients, Noise Reduction Coefficients (NRC), and Sound Transmission Class (STC), you will learn more about how they are measured and calculated. We had a previous blog (here) about mounting methods for testing, and how they simulate installations in different environments. However, in addition to different mounting methods – there are also different tests.
Different test standards with the same reported data?
Let’s say that you are looking for NRC or Sound Absorption numbers for a material – you may not know that there is both an ASTM C423 and an ISO 354 test that will give you this information. While they are comparable in many ways, there are a few variables that allow subtle differences in the measurement and calculation of these numbers. One major difference is that they allow for a different amount of material to be used in the test. The minimum test sample size for ASTM C423 is 60ft2, while the minimum in ISO 354 is 10m2 (or 107.5ft2.) The maximum amount of material is also different, with the ISO 354 maximum set to 12m2 (with an allowed increase of V/200 for rooms with a volume (V) > 200m3) and no maximum on C423.
While this variability may seem a little confusing, just remember that these tests can be run in different sized rooms with differences in setup and configuration. There are also variations in “when” the analyses begin – with the C423 starting 100-300ms after the signal is turned off and ISO 354 starting after a 5dB drop in level.
What does this mean to you?
It means that these tests don’t give you an absolutely-perfect, solid (or stable) number. The material performance values are an imperfect, but still useful, measure of performance. Even if you retest the same sample in the same room, you will likely see some variation in the results – This variation is used to calculate “Repeatability” of a test method. If you test the same material in different rooms, you are definitely going to get variation, and this variation is used to calculate “Reproducibility” of a test method. Counter-intuitively, this means that these different numbers are both accurate, even though they are not the same. From these different values, a test’s “Uncertainty” can be calculated – this is a way to show how reliable the test values are. (For information about reliability and uncertainty, read the article here.)
We know that the test results are not “pin-point” accurate values, however, they are a measure of material performance in an acoustic environment. The mounting methods will also contribute to real-world variations in performance. The E400 is a standard mounting method/test for ceiling treatments placed in a grid. This method tests the tiles or panels with a 400mm air gap behind them to simulate the plenum, or dead space, in the ceiling behind the tiles. 400mm is a very particular number equating to roughly 15.75 inches. What happens if your air gap is a different depth? Simple, you will get different results. The ISO 354 recommends 400mm for North America, 200mm for Europe, and 300mm for Japan – while the ASTM C423 test recommends 400mm, with other depths allowed as specified.
There are many potential variables here. For instance, “A” mount is mounted flat to a wall, while “D-5” mount is with a 5mm gap behind, and “J” mount is for free-hanging baffles. When comparing product performance, it is best to use results from the same test method with the mounting type closest to the real world installation method. While there may be variability in the results, you can adjust for the variation by learning about the uncertainty of a measurement.
So what exactly are these numbers?
The test results are a guide to help you select material for a space. This guide helps you to approximate how much of what type material you will need to address a problem. Acoustic problems will have a massive impact on the listening experience, and should therefore be minimized. However, you still need to pay attention to how and why you are using test numbers.
For example, if there is a 12 dB drop below 125 Hz at the listening position, you may have a node, or dead spot, that can be fixed with bass traps. Research products that are tested to work down below 125 Hz and calculate how much you need based on the absorption numbers. If, after you install the products, you have a 2 dB difference, even with all your calculations, you can chalk that up to the variability of the performance in different environments and the certainty of the test. So, you can just add a little more acoustic treatment or use an EQ to fine tune it.
Did you calculate wrong? Not exactly. The calculations may be correct, but if the uncertainty of a measurement is +/- 0.2 below 125Hz, that means that you may need to account for that in the calculation. (Many tests, and laboratory environments have a great deal of uncertainty below 125Hz.)
Sometimes, it’s better to figure high and have some extra pieces of material. How do you do that calculation? Well… if the uncertainty is +/- 0.2 @ 100 Hz and the test results say that the performance is a 0.8 @ 100 Hz – then re-run the calculation assuming that it does a 0.65 or 0.7 @ 100 Hz and you should get a little more square footage of material. That is still within the performance certainty of a measurement. You can say – with about 95% accuracy – that if this material was tested in a different lab, on a different day, under different conditions… it could have tested with those performance results as well.
So be informed!
Some quick points to remember…
- Test results vary from lab-to-lab, test-to-test, and day-to-day – even with the same material.
- Test results are not random, but vary within a range based on test reliability and certainty calculations.
- When calculating, you can compensate for these variations (to some degree.)
- When comparing products, account for the variability. If two products are similar in build, materials, and performance – but one is slightly higher or lower – there may be no practical difference at all… and the variation could simply be due to the test uncertainty.