Served on a. Porous Absorber Calculator Only thing I'd tweak about the post before mine is to buy the bigger/thicker R38 (qty 8 2'x4' batts 13" thick ~$100 at Home Cheapo)!. 2" wide. The main advantages of microperforated panels (MPP) as light, clean and easy-to-design sound absorbers were already established in the previous century [1,2,3]. 59 Reliability for Perforated Panel with Porous Absorbe. I know Jens Eklund sees Rockwool Flexibatts as an insulation material with good and appropriate air flow resistance for porous absorbers (preferably about 20 cm / 8" and thicker). 2017, 116, 311–316. The absorption is very dependent on the type of carpet and how it is made. e. The flow resistivity of the layer in Pa. This is primarily due to viscous boundary layer effects. If you can find the Gas Flow Resistivity of the product you could predict the absorption spectrum using this calculator. Reply. The angle of incidence can be adjusted. Multi-layer Absorber Calculator. E. what is your opinion about porous absorber calculators online such as: and. Share Reply Quote. The resonant frequency could be calculated using e. 1 Website for Pro Audio. To get a feeling of how much was needed to absorb any given frequency, I've been using this porous absorber calculator. wooden membranes or 3. I've been playing with the Porous Absorption Calculator a lot and am perfectly happy with the level of low freq. All the source code for this app is availble on my Github repo "porous_absorber". 90 width you are lost in regards to bass if you rely on absorption only. 90 cm) through a calculator, the benefit from more depth seems to be rather minimal. Use the formula for the wavenumber in the porous absorber in the links I provided. Look at the densities. online calculators for porous absorbers. The absorber is assumed to be in front of a. with porous absorber assuming you use the good GFR and good surface, you will need a tickness equal at 2,8 m/ 111 inch for maximum absorbtion. The angle of incidence can be adjusted. 59. I guess my only concern is that the calculation does not take into account density; and I have read many knowledgeable folk claiming a higher density for thinner panel is ideal. But this, this is a problem beyond simple Excel. There is an excel sheet available somewhere online and also this online calculator at Porous Absorber Calculator Here's a some modeled results for 100 mm thick absorber placed at a wall using different flow. 49% of the microperforated spring steel panel absorber. s/m2, at which density going beyond 12" of thickness offers minimal benefit, and getting more than 50% absorption at 50Hz doesn't work. Member. Username: Password: Forgotten password? Register home | terms of use | privacy policy | links | contact: Copyright. It's a big group effort and we're in the process of trying to make it easier to understand/use. I used theIve been experimenting with the Porous Absorber Calculator V1. Porous Absorber Calculator 2) the filtered impulse response at -60 dB or the topt can give an indication. . IB Sub. Porous Absorber Calculator. Fraunhofer developed with Caruso Iso-Bond panels the VPR absorbers th. DanDan. All the source code for this app is availble on my Github repo "porous_absorber". For the same type of porous absorber, one with a lower bulk density has a higher total porosity, resulting in a higher sound absorption coefficient (SAC) spectrum. Both are needed for accurate prediction of porous absorber performance. Delany and Bazley. The porosity of copper foam is 0. 4 0. DemetrisThe No. Glass wool fibers have poor deformation and decreased sound absorption in the. 59 Here is another: Porous Absorber Calculator The trick seems to be finding the Flow Resistivity for the material you want to use: Pa. 1. The mesh part shown in Fig. absorption offered by the 3887rayls/m. Some carefully placed spacers (smaller strips of insulation) could keep it off the wall. . If you put porous sound-absorbing material, processes in the system quit being adiabatic and the formula transforms into the following: fo=500/sqrt(m*d) Filling inner volume of the construction with sound-absorbing material reduces Q-value (Q) of the absorber, which leads to its working diapason extension. . A panel absorber consists of a flat panel made of wood, metal, gypsum board, or plastic material that is arranged in front of an enclosed air volume. I would really like to do something like this for all of my panels in my studio but I can't seem to find a good material that I can easily buy in. As a result, a combination of porous and membrane technologies should be able to absorb the vast majority of frequencies. Note the ISD gap of such rooms is very long, infinite perhaps. See below for approximations of absorption coefficients for the theoretical 21" thick R38 (blue line, absorber 1) and the 1. Model: Allard & Champoux (1992) Absorber Parameters. Mounting and. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. However, for basic calculations relating to multi-layer porous absorbers, both calculators should give almost identical results (provided the extra options in Soundflow are not used). Just don’t make the air gap deeper than the panel depth; a 1:1 ratio is best. Hi All. The actual average sound absorption coefficient of the microperforated panel + cavity + porous metal + cavity sound absorber in the 100–1800 Hz range reached 62. The collectors have the same geometry, cross-section surface area and are built from the same materials, the only difference between. Mounting and. Another theoretical test case was made by adding an air cavity to the soft porous absorber, leading to flow resistivity σ = 10 kPa. To estimate the attenuation D of silencers under practical conditions, the formula of Piening is used: D=1. This was measured and also predicted in Ethan's room mode calulator for thePorous absorbers need considerable thickness to maximize the absorption performance at low frequencies since the minimum thickness required is usually one order of magnitude smaller than the. Porous materials, particularly polymeric foams, are the most effective sound absorbers among a wide range of existing sound-absorbing materials. Absorption Area. The calculator is made for comparing various thicknesses, air gaps and materials. 1. Porous absorbers are most effective with mid to treble tones. A reset button is provided which returns all global parameters (and parameter options) to their default. Multi-layer Absorber Calculator. . In order to optimize sound absorption, it was generally advised to predict and calculate the absorption based on the dependent parameters and optimize the parameters to obtain the desired absorption. New Porous Absorber Calculator. Now you can determine which absorption you can expect from what you have. doc Porous Absorber Calculator V1. the waterfall is ok for the resonance. The lowest room mode you have between your ceiling and floor is at 75 Hz. For a porous absorber it assumes a rigid backing and that backing (ie the wall) is assumed to be air tight. Whealy C. The sound absorption coefficient calculator determines the absorption coefficient via absorbed and incident sound intensities. My Studio. As an addition I would go to Zorba and request a demo license for the program Zorba that does the same but a little different, just for checking. This sheet shows two absorption curves for a single layer of porous absorber with and without an air gap. These porous absorber models are then used to calculate the surface impedance and absorption coefficient of different absorbents using a transfer. 5αCL/A (C is the circumference, L the length, and A the. A 100mm panel with 100mm air gap gives a 0. Slotted Panel. 8 all the way down to 30 Hz. Absorber Parameters This calculator estimates the absorption coefficient of a porous aborbent in front of a rigid backing (such as a solid wall) with an optional air gap between the absorbent and the backing. Hole spacing. DD Share Reply Quote. For example, I want to absorb. His high performing new VPR one might also be loosely called a panel design. Parameter Options determine whether certain parameters appear in the Global or Absorber sections. Porous Absorber Calculator BTW, if you're from Finland: I'd go with Knauf rolls of insulation from Byggmax, which amazingly is the cheapest option and among the best (if not THE best) performer for thick. Tuned pressure absorbers work only if pressure at tuning frequency is present, they will not work i. Same Class – Different Performance. s/m2 for Roxul SNS and 24,000 Pa. Luca, You don't say whether you want corner bass traps, membrane absorbers or Helmholtz resonators. The others perform atrociously, but even the Komatsu won't work correctly for mixing different densities. Absorber thickness. Absorber Parameters This calculator estimates the absorption coefficient of a porous aborbent covered with a perforated panel. 4 Applications. I am interested in porous absorption of low frequencies since it is. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. Membrane resonators can be calculated with the Excel Spreadsheet Porous Absorber Calculator V1. If you put porous sound-absorbing material, processes in the system quit being adiabatic and the formula transforms into the following: fo=500/sqrt(m*d) Filling inner volume of the construction with sound-absorbing material reduces Q-value (Q) of the absorber, which leads to its working diapason extension. 9615% and 73. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. A thought occured regarding the tuning of these panels. 2m depth in my calculations is only for hangers. Today I did comparative measurements with. 59 for this job?In this study, the best-fit approach proposed by Berardi and Iannace was employed to calculate the (c_{1} - c_{8}) coefficients for the ASFs samples by fitting the experimental results to Eqs. If the stuff you have is flexible building insulation, 8000-10000 Pa. It was treated with nearly completely closed surfaces composed of thick porous absorbers, with themselves were touchingly mounted behind 1. The distance in mm between the perforated panel and the porous absorbent. Porous Absorber Calculator Global Parameters affect all absorbers. Here is a list of other nice acoustic tools you can enjoy. Example of a 10cm porous absorber. hi Jens, thanks for replying, from reading a few threads i see you have much more experience than I in making helmholtz absorbers. See here for a simple porous absorber calculator. 30th May 2012 #27. The purpose of this blog is not to explain any of the principles of acoustics or how to interpret the data plotted on the graphs shown below, but rather to describe the architecture of a browser-based WebAssembly application written in Rust. Here's the link: Porous Absorber Calculator. Show abstract. Porous Absorber Calculator. the direct path angle/evctor is irrelevant. 35 absorbtion at 30Hz and increase to 0. Username: Password: Forgotten password? Register home | terms of use | privacy policy | links | contact: Copyright. Share Reply Quote. Porous Absorber Calculator. com. Turns out that my 4" (10cm). s. This article focuses on how to calculate the absorption coefficient by placing porous absorbers in front of a wall or other hard surfaces. Rigid backing. Porous materials are capable of absorbing low frequency sounds, but in many applications the depth of absorber needed to absorb low frequencies is not feasible. 52 and download the Porous absorber calculator. Username: Password: Forgotten password? Register: Calculator. Porous absorber. If you use lower GFR the Q is widened but damping is lowered. When set to "Absorber", the model can be set individually for each absorber. Absorptive treatment such as mineral wool, glass fiber or high-porosity foams reduces reflection sound. Foams and granular materials like porous. 5 m for the porous absorber to hit the quarter wavelength. The No. The ZORBA software is a tool for calculating the sound absorption coefficient of porous materials and perforated surfaces. I read the "repeat distance" value as the distance between each hole in a square grid. 59 We've sorta accepted that higher mass = better NRC and STC, which is generlly true compared to foam for a bass trap, but there is more to it than just. Helmholtz Absorber Calculator. Leave a Reply Cancel Reply. The proposed sound absorber design is an evolution of the two-segment SeMSA design to a more complex multi-sector design. Put in very simple terms, in velocity based absorption, kinetic energy is dissipated as heat via the traversing of what is referred to as a 'torturous' path. BEHOLD THE MIGHTY POROUS ABSORBER CALCULATOR. 16,600 is OC703, 5000 is fluffy. • Absorber 1. Here are some common values for absorption materials. 8 kg/m3 can be alternatives. . What airflow resistivity number should I use in AM porous absorber calculator if I were to model 4" 4pcf Thermafiber Safing (the one carried by Menards) ? thank you 1. This work investigates the use of hybrid double-layer microperforated panel/porous systems as wideband absorbers for applications in the closing of the test area of wind tunnels. For the sake of completeness, the technical parameters that I used for my curves: air temperature: 20 degrees Celsius, air pressure: 101325 Pa, Angle of Incidence. ZORBA is currently available in version v3. The sound dissipation mechanism in MPPs is based on the principle of the Helmholtz resonator (HR) []. Forum Donor. Wherein, there is a cylindrical porous absorber which is sealed behind a quartz window. Truth be told it's closer to 42Hz. On one of the 4. For DIY absorber components please see: Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page Absorbtion coefficents, averaged to the octave bands, do not nessessarily tell the whole story. You can use the Acoustics Module to model the propagation of elastic waves in solids and porous materials, for single-physics or multiphysics applications, such as vibration control, nondestructive testing (NDT), or mechanical feedback. 1) why do my. Porous Absorber Calculator. Select frequency range : 20 - 300 Hz. A fully absorbent back wall is a fundamental of the Non Environment type of room. Actually it doesn't. 4 inch absorbers have proven sound absorption values up to alpha = 0. The nice absorber calculator you posted only confirms: 10cm is useless under 100Hz, 20cm does very little and more is physically impossible. That said, we get back to this question. Gushue ️. Play around with the flow resistivity on a porous absorber calculator. g. You can space the panels off the wall as you wish, there is no problem with what you want to do. Porous Absorpton calculator says: No significant absorption for bass lower than 150 Hz: In a room with 1. Maybe with tuned absorbers or perforated panels, but there are others here that have more experience with that. how to predict the behaviour of a Gobo - Gearspace. Air-backed porous absorber (i. effect_of_perforated_sheet_open_area. Carpet on the floor and broadband absorbers covering most of the ceiling. Have a look at what happens with 100mm panels AND a 50mm air gap though just out of curiosity, and also see what happens with a 100mm air gap: Porous Absorber Calculator - Results Well worth pulling them out as much as you can, up to their own depth or a bit more. So attempts to calculate or predict absorption using a calculator based on a single depth are futile. GameStop Moderna Pfizer Johnson & Johnson AstraZeneca Walgreens Best Buy Novavax SpaceX Tesla. Up to four absorbers can be modelled at once, each of which can have up to four layers. Ye Old Porous Absorber Calculator. By exciting a room mode from 2 sources with opposing phase, the corresponding peak or dip in frequency response is reduced or removed entirely. Given frequency : Hz. How does one calculate or predict a perforated panel with porous absorber when the shape is triangular? I was thinking of building a superchunk-style p. This calculator estimates the absorption coefficients of multi layer porous aborbers. The frictional resistance given from the material is enough to stop the wave and convert it into heat energy. I was pretty psych'd initially but then became a bit confused and frustrated by a few things, not the least of which is the variety of GFRs listed for OC703. . 5°, and between the (Flat plate and metal foam 40 PPI) absorber plate was 8. Acoust. How the Porous Media Flow Module Helps Improve Your ModelingA resonant absorber is a vibrational system that “runs” on sound pressure. A higher fiber density leads to a more complex path inside the porous absorber therefore it implies higher interaction between sound waves and fibers. . I was pretty psych'd initially but then became a bit confused and frustrated by a few things, not the least of which is the variety of GFRs listed for OC703. The ZORBA software is a tool for calculating the sound absorption coefficient of porous materials and perforated surfaces. Adding an air gap between the. Agreement to Terms of Use This website is offered to you by acousticmodelling. ( this is mBuy Kinsler & Frey "Fundamentals of Acoustics" 2nd edition, look up how the boundary impedance of such an arrangement is calculated based on the Delaney-Bazley theory for porous absorbers, calculate the reflection coefficient for normal incidence, and vary the flow resistivity to minimise the reflection coefficient for a given arrangement. This means you can vary the angle at which the sound waves (plane waves) hit the surface of the porous absorber. Long story short, when you have two materials, lets say one has 6kPa/m2 and another wit 12kPa/m2. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. DanDan. Congyun and Qibai (2005) calculated the acoustic impedance for multi-layer absorbers such as perforated plates and air space or perforated plates and porous materials by using an iterative method. The air gap behind the absorbing material will effectively act as if the absorber would go all the way to the wall. Multi-layer absorbers composed of perforated plates, airspaces or porous materials are used widely to absorb broadband noise [1], [2]. Calculates the absorption curve of various porous absorber systems. Abstract. s/m2, a 2ft thick absorber can be 70% effective at 50Hz. How would you calculate a triangular trap and compare different flow resistivities? Do you just pick the different depths of the triangle and look for an average?I was playing around with the Porous Absorber calculator but I don't see how to input the difference between 703 and 705. Yeah, for porous absorbers, lower GFR is better for LF absorbtion, but the thicker the trap needs to be. Helmholtz Absorber Calculator. . s/m2 flow resistivity. Porous absorbers. The main dimensions of packing were the following: 10 mm height, 146 mm inner diameter, 600 mm outer diameter; the specific area was 2800 m 2 m-3 and the porosity 0. I know questions about this calculator have come up many times so I'm sure this topic has been covered, but there's just so much info on this forum, much of it contradictory, it's rabbit holes all the way down. Can these be converted to Flow resistivity Pa*s/m2 ? (to be used in porous absorber calculator) Share Reply Quote. ↑ top; home; New Product Alert; classifieds; reviews; deal zoneThe distance between the holes (centre to centre) in mm. Like other resonance absorbers, they can be tuned to specific frequencies, but they can also be used in conjunction with porous absorbers, such as with applied foams, for broadband applications. Helmholtz Absorber Calculator. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. Porous Absorber Calculator. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. AFAICS, the. Flow resistance is the main property that sets the different types of materials apart. 1 (a) that comprises a cavity, neck, lids and porous material. I have a crazy 125hz problem in my room and I haven't had luck fixing it with corner traps or speaker placement, and being that its quite narrow, I want to build some tuned traps (PPA Helmholtz) but there seems to be differing opinions on whether the heigFig. Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. From the first formula we can calculate specific airflow resistance simply by multiplying airflow resistivity [Pas/m2] with thickness of the porous material [m]. You can play with the porous absorber calculator to find suitable dimensions. no backing) For the air-backed absorber geometry, Strutt also allows the calculation of the transmission loss through the porous material. Porous absorber I already have and it is not enough for my frequency. Thickness of the template is 1/8” = 3,175 mm. Is the “Rigid Backed Porous Absorber” calculator not “correct” (within reasonable limits of course)?. 21st March 2012 | Show parent #14. This only works with absorbers of uniform thickness and triangular bass traps obviously have varying thickness. Porous Absorber Calculator. If you drop down to about 4K Pa. Often porous materials with spherical grains have lower porosity than materials composed of non-spherical grain. 5th August 2017 #5. Some things were way off. The absorber geometry is still cylindrical, but instead of being subdivided into two segments the cylindrical volume is subdivided into N sectors. Width of hangers is used to define lowest frequency, membrane absorbers isn't included in this simple model/formula, and 1. This work presents the use of a porous-media approach for computational fluid dynamics (CFD) modelling of wave interaction with thin perforated sheets and cylinders. (to be used in porous absorber calculator) Share Reply Quote. 4 0. Typical mineral wool is about 8-10K Pa. Having that much depth allows me to absorb lower but it creates. The available calculators allow you to see the impact of this absorber on the absorbers frequency response for different depths and spacings. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. 16000, 23400, 27000 (c/o NASA!). Originally Posted by Kyle P. Membrane resonators can be calculated with the Excel Spreadsheet Porous Absorber Calculator V1. I am using this link Porous Absorber Calculator and using a rockwool product with a 70kg/m3 density and around 30kPa. For sure. All formulas and units are the same in NASA. Multi-layer Absorber Calculator. Sound is attenuated due to viscous friction in the submillimeter size pores. Share Reply Quote. 0 with a German user interface and is developed by Marshall Day Acoustics. The temperature profile is also shown in longitudinal direction in different angles for the configuration VI and the non-porous state in this igure. "Absorber 3" would be the side walls, mostly starting at hip height and touching the ceiling. - the area covered with the absorbers is not large enough (you mention 36Hz, which is a wave of 9. Flow resistivity. Absorber ParametersHi I just wanted to share an alternative design for absorbers that i made in my listening room. I found Whealy's Porous Absorber Calculator and the math is beyond casual skimming and just typing it in. This paper shows that the predictions from impedance tube measurement and the empirical method have reasonable accuracy for the determination of the random incidence SAC above 400 Hz. It will let you model various combinations of panel width, air gap, and material type. If you change the vibrating mass and stiffness of the. not easy but it's doable. Hope you find it useful. 50%) 400mm Porous Absorbent, 4000 Pa. s/m 2. There is also a loss in momentum due to. The complete way for calculating this would be to feed the data into a finite elements simulation. On a microscopic scale, sound propagation in porous materials is generally difficult to study because of the complicated geometries of the frames. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. The Chris Whealy calculator can help with Helmholtz. 8 At 2000Hz, respectively. 5k for OC703 (ignoring the NASA vs. This was supposed to be a good alternative to 703 rigid fiberglass yet when I input 4 inches / 10cm of absorption with these figures into the calculator, the results are rather bad. Porous Absorber Calculator. Similarly the BBC settled on a Panel design, again after much research. Tortuosity was essential a capacitance test with a wetted material. Porous Absorber Calculator. (notice the. meter. These porous absorber models are then used to calculate the surface impedance and absorption coefficient of different absorbents using a transfer matrix approach. But in my design, the open area will also be roughly 50%, so I figured the results would be useful anyway. The first step is to calculate the volume of the room and the room surface area, which are V = 144 m 3 and S = 180 m 2,. com are 34 inches wide. My questions are: 1. s/m 2. Porous Absorber Calculator. The collectors have the same geometry, cross-section surface area and are built from the same materials, the only difference between them being the absorbers. For DIY absorber components please see: Bob Golds Fiberglass/Rockwool Absorbtion Coefficients page Absorbtion coefficents, averaged to the octave bands, do not nessessarily tell the whole story. 2022-03-07 11:11 am #1 2022-03-07 11:11 am #1Calculate Optimal Gap Size for Given Frequency. The thickness of the sound absorber was changed from d: [1. For membrane absorbers, a first approximation is k/sqrt(d*M), where k is between 50 and 60, M is the mass-per-unit-area of the membrane (kg/m^2) and d is the sealed cavity. Therefore, recent time-domain solvers. ZORBA is currently available in version v3. This porous absorber calculator will help you compare the effectiveness you can expect with various depths. Caruso absorber panels are one of the most economic and efficient acoustic treatments. Thermohanf porous absorbers. Air gap 1. Porous Absorber Calculator Preamble. feet. Mechel and Ggrundmann. Each. The particle velocity is at maximum at 90° and 270° (Vmax) and minimum at 0° and 180° (Vmin). PaulRain. Multiphysics couplings are essential to capture the effects of porous media on transport processes. When modeling porous absorbers, various empirical models are available. not registered yet? join now! login: join with facebook. The lowest room mode you have between your ceiling and floor is at 75 Hz. The spring is the air inside the cavity of the resonant absorber. Broadband absorber and gas flow resistivity. The WLG-045 is best for deep porous absorbers, i think about 3k rayl; about 50cm of it is the most efficient, gets you absorption down to 50Hz easily. 1 Website for Pro Audio ; The No. Normal incidence. What I wanna try is to build something like this:. Porous Absorber Calculator. Porous materials, particularly polymeric foams, are the most effective sound absorbers among a wide range of existing sound-absorbing materials. How the Porous Media Flow Module Helps Improve Your Modeling Absorber Parameters This calculator estimates the absorption coefficient of a porous aborbent in front of a rigid backing (such as a solid wall) with an optional air gap between. This was supposed to be a good alternative to 703 rigid fiberglass yet when I input 4 inches / 10cm of absorption with these figures into the calculator, the results are rather bad. First Reflection Calculators Wavelength - Frequency Calculator Calculate Room Modes Calculate optimal Room Dimension Reverb (RT60) Calculator The Wall Behind The Loudspeaker Absorbers Helmholtz. Long story short, when you have two materials, lets say one has 6kPa/m2 and another wit 12kPa/m2. When tailoring porous absorbers in acoustic applications, an appropriate acoustic material model, as well as the relationship between the material model parameters and the microscale geometry of the material, is indispensable. diffusors depending on geometry plus a minimum of porous absorbers behind thin (5. If you download and play with the porous absorber calculator: Porous Absorber Calculator V1. 1. 5" rockwool on the wall (green line, absorber 2,. June 21, 2019. 9th January. (the theorical thickness is equal to the 1/4 wave length). I'm playing around with porous absorber calculator and trying to find a good balance between effective and practical. You should be fine with 11 inches from the back wall to the speakers. 's most successful trap, after many many attempts, was a panel one. Porous concrete can mitigate noise at a lower frequency than a commercial porous absorber with the same thickness (foams or glass wool) due to high tortuosity. 8 & you will see the LF absorption. The composite sound absorber includes a MPP (micro-perforated panel) layer, a porous material layer, and an air cavity layer. To calculate the effective coefficient of thermal conductivity of porous absorbers, the simulation was carried out without air movement inside. I am using values of 10,000 Pa. Porous Absorber Calculator. This leads to the question of how much more? In acoustics, we have the ultimate arbiter of test data. If I want to calculate an optimal GFR for a given depth of porous absorber, how would I do that with a formula? Share Reply Quote. g. But I think I have a much better understanding now, especially thanks to the Porous Absorber Calculator (the excel spreadsheet). Guest. . Komatsu model is selectable from the porous absorber calculator's menu and is the best to use. 5 rayl/m. June 21, 2019. 59 Play around with with 6 kpa equal to 6000 rayls. Personally, I think it's the better option. 58 of Porous Absorber Calculator. , JH Brant, DanDan, Avare, can't name you all. 8 1 Absorption Coefficient. Jens. Limp membrane, Helmholtz, or just open, all models require you to place the porous absorber at the front for maximum effect, but sometimes with a minimum air gap so it doesn't touch the front. Up to four absorbers can be modelled at once, each of which can have up to four layers. The 2 inches of linacoustic material behind my false wall did wonders for the sound quality of the room! sirjaymz.