Mathematical models have been developed to evaluate the dynamic behavior of two solar air collectors: the first one is equipped with a V-porous absorber and the second one with a U-corrugated absorber. As. All the source code for this app is availble on my Github repo "porous_absorber". The air gap behind the absorbing material will effectively act as if the absorber would go all the way to the wall. In this study, porous packing was used. Hello, a broadband panel effective at 30 hz is not yet invented. OC discrepancy), 30k for 705 - I think what I have is closer to OC703, but I have a call in to Knauf to see if. So attempts to calculate or predict absorption using a calculator based on a single depth are futile. For example, I want to absorb. Damping is generally achieved by a combination of three processes: resonances that trap the acoustic energy at given frequencies, absorption of acoustic energy by different porous and fibrous lining materials, and losses in perforated plates, also known as perforates. Speech Reinforcement Calculator The damped walls are acting as membrane absorbers below that range, requiring an additional 30-45 cm air gap, to absorb down to 20 Hz. 4 Applications. According to the "Porous absorber calculator" spreadsheet, using a 15000 rayls/m flow resistivity, a 100mm (4") panel with a 330mm (1ft) airspace behind it (e. Caruso absorber panels are one of the most economic and efficient acoustic treatments. 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. Liu, G. 5th August 2017 #5. (i found URSA pureone fibre to be a good product available in my area) here is a great calculator to predict what is going to happen: Porous Absorber Calculator in acoustically small rooms like yours resulting roomresponse is probably too dry after treating the lows. The particle velocity is at maximum at 90° and 270° (Vmax) and minimum at 0° and 180° (Vmin). Porous Absorber Calculator V1. Using the "stanleyhall" and "whealy" calculator I figured out, that this could be done best using porous material with a quite low GFR at around 1. To get a feeling of how much was needed to absorb any given frequency, I've been using this porous absorber calculator. Global Parameters affect all absorbers. Your key says they are all rigid porous absorbers. Member. Way back, G. Porous Absorber Calculator. 58 (RPG´s BAD template is 600x600 mm with 512 holes, each Ø12,7 mm. Unless care is taken when deciding on the size of the absorber unit, these holes will not add up. A microperforated panel absorber may have an absorbtion curve like this. Multi-layer Absorber Calculator. 1. Just made a massive front corner trap out of Knauf RS45. When set to "Absorber", the model can be set individually for each absorber. Show abstract. Helmholtz Absorber Calculator. m −2 and thickness h = 150 mm. 1 (b). I am quite a noob but i’ve been researching a lot about it the past few weeks. CryptoApplication of Porous Metals. Just don’t make the air gap deeper than the panel depth; a 1:1 ratio is best. Example of a 10cm porous absorber. Perforated absorbers are lighter in weight than diaphragmatic absorbers and are for absorbing in the low middle. Another important parameter of sound absorption, besides the absorbers design, is its AREA. I was making porous absorber calculations on a multilayer absorber calculator. 55 at 125 Hz for. Porous Absorber Calculator. 9 and its pore density. Air gap 1. Numerous computational models to map the acoustic effectiveness of open-porous absorbers are available for your design, for example: empirical model of. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. . Flow resistivity. In contrast, a 300mm chunk with zero. Oh well, experimentally bruteforcing it. These Website Terms of Use apply to the entire contents of this website under the. Have a look at the porous acoustic modeling/calculators. June 21, 2019. This app is designed to assist acousticians when designing environments such as home cinemas. Toyoda, E. Multiphysics couplings are essential to capture the effects of porous media on transport processes. Multi-layer Absorber Calculator. Actually it doesn't. Absorber thickness. Here is probably a good place to promote this relatively new Porous Absorption Calculator, thanks to Demetris. Porous silicon carbide (SiC) is widely used as the absorber due to its high-conductivity, high-absorption, and anti-oxidation [12]. If you drop down to about 4K Pa. Slotted Panel. 2m porous absorber, 1. It models resistance to flow only. Quite a bit of comb filtering in there but. 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,. To estimate the attenuation D of silencers under practical conditions, the formula of Piening is used: D=1. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. Polyurethane (PU) foams have become the most important class of polymeric foams for sound absorption applications because of their low density, lightweight, good mechanical properties, and ease of. s/m 2. However we can get into the ballpark with a few simplifications. Porous Absorber Calculator And some more courtesy of Sebq Bradford Rockwool Building Blanket 13000 mks Rayls/m (nominally 30kg/m^3 product) Bradford FIBERTEX ™ 350 Rockwool 22000 (60kg/m^3) Bradford. A cylindrical geometry is used so that the multi-sector SeMSA. Use diffrent angels because base resonances come from everywhere. If you're interested you can find a very good spreadsheet from Chris Whealy to (theoretically) predict absorption based on "gasflow resistance" (the word you were looking for) Acoustic Calculation Tools It's the Porous Absorber Calculator file. 69%, which was superior to that 25. Porous Absorber Calculator. Global Parameters affect all absorbers. Absorber thickness. you are inputting the incident angle of the specular energy with respect to the absorber panel. The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. 16000, 23400, 27000 (c/o NASA!). 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. Furthermore, if you have a look at Chris Whealy's Porous Absorber Calculator and plug the numbers for the frequency range of absorption for regular fiberglass batt insulation (R-13) @ about 8000 rayls/m compared to 60kg rock wool @ about 22000 rayls/m. IMO perfect tuned absorber it's a "virtual hole" for sound wave with a given frequency. 9 log(fd)−X. The effect of the porous absorber is analagous to a damped mass/spring system, so yes the Q does increase with the damping coefficient and eventually becomes "overdamped" in the extreme when full of very dense mineral wool. i think that most isolation material or foam benefit from stacking in depth and make bass trap from it. 1) why do my. The prediction models are usually used to theoretically calculate the energy consumption efficiency of the porous sound absorption materials, which could provide guidance for the structure design of porous sound absorption materials. 8 1 Absorption Coefficient • 5000 mks rayls/m • 30000 mks rayls/mPorous Absorber Calculator V1. Now you can determine which absorption you can expect from what you have. I'm only taking axial modes into account. 5rayls/m) 1200mm Porous Absorbent, 1500 Pa. This is the number we're after. The porous absorber calculator is accurate as far as it goes but it does not take this effect into account and therefore you usually see higher low frequency absorption in tests than the calculator predicts. Let’s assume a 10 cm porous absorber backed by a 10 cm air cavity, which is quite common for ceiling absorbers. Which one would you place closer to the wall when building a porous. So the true effective depth for a gapped porous absorber is more than 1. 9615% and 73. 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. Tortuosity was essential a capacitance test with a wetted material. It claims to be capable of calculating the absorption -coefficient for multilayer absorbers. When set to "Absorber", the model can be set individually for each absorber. Porous Absorpton calculator says: No significant absorption for bass lower than 150 Hz: In a room with 1. Truth be told it's closer to 42Hz. The mass is the cabinet and front wall or diaphragm. From the first formula we can calculate specific airflow resistance simply by multiplying airflow resistivity [Pas/m2] with thickness of the porous material [m]. Personally, I think it's the better option. 59. The thickness of the porous absorbent in mm. 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. 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. Mathematical models have been developed to evaluate the dynamic behavior of two solar air collectors: the first one is equipped with a V-porous absorber and the second one with a U-corrugated absorber. You should be fine with 11 inches from the back wall to the speakers. 0. com. 59 There are also some interesting studies from the BBC and NASA which support this approach. A 2" cloud with 16800 Pa*s/m² (which should be about the value for Owens Corning 703) mounted to the ceiling (1 mm gap) absorbs less than 50% below 428 Hz and less than 25 % below 269 Hz, and practically nothing at 75 Hz. Porous absorbers are in fact thermal materials and usually not effective sound barriers. But none with just a plaster board in front with an absorber and air gap. 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. 5k for OC703 (ignoring the NASA vs. If you know any other quality tools, please tell me! List of other quality acoustic calculators besides amcoustics. First, the surface porosity, defined as the ratio of the main perforation surface area to the front surface area of the absorber, is much lower than that of a conventional porous absorber. I do all my caculation with the Porous Absorber Calculator. Hello ! First post but i'm reading for years Thank to everybody who shares so much great info ! ( Thomas Northward, Boggy, GE, Jens E. 3 to 2 kg/m² (most probably between 0. Foams and granular materials like porous. Sound-absorbing performance of copy paper composites with bulk densities below 442. The air volume is partly or completely filled with mineral wool or foam. s/m2 for Absorber 1, then. 1. 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. 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. 4 0. IB Sub. There are generally two types of bass traps: resonant absorbers and porous absorbers. Calculates the absorption curve of various porous absorber systems. Mass Production is often uncommercial, although some companies offer membrane absorbers. 5" rockwool on the wall (green line, absorber 2,. Porous Absorber Calculator. Porous Absorber Calculator. In addition to Jens' suggestion (which you'll need Excel to use), there is a free online calculator for air flow resistivity here: Porous Absorber Calculator You can mostly use the default settings, but choose Miki (recommended by the developer) and random incidence, then type in thickness in millimeters, and 7000 Pa. 2m depth in my calculations is only for hangers. Multi-layer Absorber Calculator. The proposed sound absorber design is an evolution of the two-segment SeMSA design to a more complex multi-sector design. Another important parameter of sound absorption, besides the absorbers design, is its AREA. For 60 cm the situation is similar, though with different frequency and angle values. 2m wide, 1. Impedance prediction methods have been published by Delany and Bazley, Qunli, Miki, Mechel, Mechel and Vér, Komatsu, and Allard and Champoux. When paired with a porous acoustic core, they present a wider more linear absorption coefficient, making them a preferred option. Porous absorbers, as the name would suggest, are made from a multitude of tiny holes – cells, through which sound travels. Hope you find it useful. DemetrisThe No. The mass is the cabinet and front wall or diaphragm. s/m 2 (porous absorbent). 1. 1 (a) that comprises a cavity, neck, lids and porous material. Porous model: Allard and Champoux (1992) Helmholtz model: Ingard/Allard. Guest. 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. 8 kg/m3 can be alternatives. The best gap size for the given frequency =. Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. So correct me if I'm wrong, but the thicker the absorber and air gap, the lower the frequencies you can absorb BUT as those factors change, the ideal absorber changes as well. Tuned pressure absorbers work only if pressure at tuning frequency is present, they will not work i. It will let you model various combinations of panel width, air gap, and material type. . We can ignore the imaginary term in the equation. This leads to the question of how much more? In acoustics, we have the ultimate arbiter of test data. Here's the link: Porous Absorber Calculator I believe that it's working correctly and is stable but would appreciate some feedback if you have any problems with it. Parameters Global Parameters Air temperature: 20°C Air pressure: 101325 Pa X Axis: Frequency Range: 20Hz - 10000Hz Scale: logarithmic Resolution: medium Angle of. Flow resistivity: The flow resistivity of the layer in Pa. Reticulate porous ceramic reactors use foam-type absorbers in their operation which must fulfill two essential functions: favoring the volumetric effect and increasing the mass and heat transfer. (download open office if needed, it's a free!) As you'll see, friction absorbers are not particularly effective at such low frequencies unless extremely deep. straddling a corner) will give you a 0. Porous Absorber Calculator V1. Porous Absorber Calculator Preamble. Guest. g. Model: Allard & Champoux (1992) Absorber Parameters. Same Class – Different Performance. (18), (19)) are used to calculate the Nusselt number and the Darcy-Weisbach friction factor, respectively [46, 47]. They achieve a high- absorption coefficient, utilizing a relatively small volume. This app is designed to assist acousticians when designing environments such as home cinemas. Therefore, recent time-domain solvers. I have been using the porous absorber calculator and sound flow, and have read Everest and the helmholtz part of Acoustic Absorbers and diffusers, but still have many questions. That said, we get back to this question. 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. Calculate the cubic packing of uniform spheres porosity (Figure 2‑8). This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. 1 Website for Pro Audio ; The No. 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. Here is the link to the Porous Absorber Calculator. 2)12 inch of Roxul Safe N Sound Floor to ceiling. When length of the cavity was 20 mm, average sound absorbing coefficient of the compressed and microperforated porous metal panel absorber in frequency range 100–6000 Hz reached 59. 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. Hey guys, I need broadband absorption down to 50Hz. 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. Application areas range from micromechanical devices to seismic wave propagation. 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. 58 it's very clear. 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. The angle of incidence can be adjusted. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. Flow resistance is the main property that sets the different types of materials apart. This article focuses on how to calculate the absorption coefficient by placing porous absorbers in front of a wall or other hard surfaces. Hello again! I have some challenges in my room, and been reading up on alot of stuff. 6 0. Having that much depth allows me to absorb lower but it creates. 5 @ 500Hz, and 0. But in my design, the open area will also be roughly 50%, so I figured the results would be useful anyway. Multi-layer absorbers composed of perforated plates, airspaces or porous materials are used widely to absorb broadband noise [1], [2]. hi guys trying to figure out which of these 2 products would be ideal for bass trapping. If you can find the Gas Flow Resistivity of the product you could predict the absorption spectrum using this calculator. C0 is the speed of sound in air, which we'll say is 343 m/s. Step 1: Cut The Wood. Porous Absorber Calculator tlindaas, did you, will you, or may I, repeat the content of this post over in the GFR gathering thread? Common Gas Flow Resistivity numbers. Thus, an MPPA layer with an attached porous material layer in front of an airgap makes the MPPA absorber more. Users with access to the relevant academic papers. This only works with absorbers of uniform thickness and triangular bass traps obviously have varying thickness. (the blue and red are OC703). These panels are. It doesn't perform as a whole system with a cavity (which isn't sealed), it's rather a velocity based absorber which. When sound propagates in small spaces, such as the interconnected pores of a porous absorber, it loses energy. Perforated Panel. Running your suggested depths (70cm vs. All the source code for this app is availble on my Github repo "porous_absorber". 16000, 23400, 27000 (c/o NASA!). I previously made some cube shaped 30 cm deep blocks, which my wife was not too fond of, so when i needed some absorbers for treatment of 1st refleksions I went with this circular design, which my wife is actually quite happy with. 064–0. Each. . Joined Nov 15, 2020 Messages 7,363 Likes 7,810 Location Brussels,. It calculates the acoustic absorption curve of a. , JH Brant, DanDan, Avare, can't name you all. -Assume you have a 12 dB peak at 100Hz that you want to treat. Absorbtion figures for perforated panels with absorber behind,. Modeling the Damping Effect. 8 1 Absorption Coefficient • bass trap1 • bass trap2 • side panel • back panelMembrane absorbers work best with lower-frequency and bass frequencies. Porous Absorbers. Some things were way off. there are many, like cotton batts, fabric acoustic panels, and any porous. The materials used to fabricate the porous sound absorbers mainly involve stainless steel [62], copper. Username: Password: Forgotten password? Register 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. These briefly and simply cover the basics (and have lots of pictures ). 1. A 2BA/multiBA setup will help. The sound absorption coefficient calculator determines the absorption coefficient via absorbed and incident sound intensities. Hello, a broadband panel effective at 30 hz is not yet invented. . Try this calculator: Porous Absorber Calculator Generally, the thinner the absorber, the higher the resistivity needs to be. When sound propagates in small spaces, such as the interconnected pores of a porous absorber, it loses energy. Acoustic plate absorbers have NRC ratings of 0. V-corrugated absorbers have been. A 2" cloud with 16800 Pa*s/m² (which should be about the value for Owens Corning 703) mounted to the ceiling (1 mm gap) absorbs less than 50% below 428 Hz and less than 25 % below 269 Hz, and practically nothing at 75 Hz. The sound absorption coefficient (SAC) of a composite multi-cell sound absorber in the low- and mid-frequency range is investigated by using experiment and numerical method. -AlsoAndre, I have been messing around with some numbers with a porous absorber calculator and I seem to be getting really good results with 8" of a ~8000 Pa*s/(m^3) absorber with an 8" airgap. 703 and other 48KG materials, have been tested and show to perform extremely well in the bigger SuperChunks, down to 35Hz in one instance. The calculation doesn't assume a sealed cavity, except for a resonator. A fully absorbent back wall is a fundamental of the Non Environment type of room. Rigid Backed Porous Absorber. For a porous absorber it assumes a rigid backing and that backing (ie the wall) is assumed to be air tight. They are usable with. Note the ISD gap of such rooms is very long, infinite perhaps. Figure 2-8: Typical ordered porous medium structures. I am currently trying to design a slotted panel with a resonant frequency of 133 Hz and I really need to know if I can use PAC at all. The formula is: \alpha_m = A / S αm = A/S. Multi-layer Absorber Calculator Please note that there are many factors which aren't taken into account, eg. My Studio. acousticmodelling - Porous Absorber Calculator The remaining room modes, usually 80Hz and below, are best managed through a combination of multiple subwoofers and good seating locations. Some carefully placed spacers (smaller strips of insulation) could keep it off the wall. I need to make a keyboard macro with that sentence. 173. The spring is the air inside the cavity of the resonant absorber. Goes up to 170/KG/M3. 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. 2017, 116, 311–316. Porous Absorber Calculator. Low densities seem good for broadband traps if thick enough. . Play around with the flow resistivity on a porous absorber calculator. Room modes mess up everything below about 300Hz. 49% of the microperforated spring steel panel absorber. It was treated with nearly completely closed surfaces composed of thick porous absorbers, with themselves were touchingly mounted behind 1. ↑ top; home; New Product Alert; classifieds; reviews; deal zoneAt high frequencies, i. Coates and Kierzkowski in their paper describe the advantages of thin, light membranes that can replace traditional bulky and economically disadvantageous porous absorbers. Either one wants low GFR and doesn't compress, or compress as a way to emulate the higher GFR of OC 703. 20 per sq metre the Fibertex 350 is 60kg/m^3, comes in 1500*900*50mm sheets and is $20. The calculator is made for comparing various thicknesses, air gaps and materials. 2 0. The frictional resistance given from the material is enough to stop the wave and convert it into heat energy. The calculators can save you from having to tear stuff out that is worse than it was: Porous Absorber Calculator V1. and the porous material layer was established by using Delany and Bazley’s model. If the cavity is filled with porous absorbent, then the system is no longer adiabatic, and an isothermal case should be considered. Its value ranges from 0 to 1, with 1 being the perfect absorber. Porous Absorber Calculator - Results According to the calculator, you will still get significant (I consider anything over . 6m walls, there is a 2. Rs=r*d [Pas/m] When you have specific airflow resistance Rs then you can calculate air flow resistivity r for any thickness; r=Rs/d. But Basotect has a coefficient of 0,8 at about 800Hz while Sonorock reaches the same value at about 1,2kHz. These calculators may not be very accurate, especially for more complex scenarios such as mixing materials. Figure 7 Figure 7: The absorption of carpets varies greatly. If the stuff you have is flexible building insulation, 8000-10000 Pa. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. . Layer 3: 240mm porous absorbent, 5000 Pa. A porous absorber may have an absorbtion curve like this. Tortuosity is a measure of path length within the material. For example, the angle of incidence can be set as a global parameter. this formula or e. abdo123 Master Contributor. First, you need to draw symmetry line in the room on the floor (I use coloured pvc electrical isolation tape, for "drawing"), but before that, you need to find it, i mean you need to find best possible symmetry in the room. If you download and play with the porous absorber calculator: Porous Absorber Calculator V1. Up to four absorbers can be modelled at once, each of which can have up to four layers. Flow resistivity. New Porous Absorber Calculator. This sheet shows two absorption curves for a single layer of porous absorber with and without an air gap. On one of the 4. Most importantly, these results should match those in the papers written by the people who developed the models. Hot links: HToM July-2015. The collectors have the same geometry, cross-section surface area and are built from the same materials, the only difference between. 6 0. The curve changes a bit as I vary the air flow resistivity (I'm using roughly. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. BTW, I prefer the Komatsu model over the default model of the online calculator. Sound is attenuated due to viscous friction in the submillimeter size pores. com, are committed to protecting and respecting your privacy and take this very seriously. 30th May 2012 #27. when using the porous absorber calculator, etc. The angle of incidence can be adjusted. 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. Abstract. 5αCL/A (C is the circumference, L the length, and A the cross‐sectional area of the absorbing duct). Thank you Can you help me clarify the difference between "random incidence" and "normal incidence" options in the porous absorber calculator? Share Reply Quote. Porous Absorber Calculator. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. Multiphysics couplings are essential to capture the effects of porous media on transport processes. Porous Absorber Calculator (by Chris Whealy) ⚠️ Downloads an exel file; Various Acoustic Calculation Tools (by Chris Whealy) Drawings: 104 Broadband 4″ (10 cm) The purpose of this thread is to explain how to both physically hook up the connections between your computer and AVR/Pre-Pro to get started with REW (Room EQ Wizard) and to share information on the proper use of REW including proper techniques for both measuring and interpreting graphs, what. Mounting and. perforated wood over acoustic foam porous absorbers. you may not need to be terribly concerned with the. This will be against a wall, not in a corner. . Save Share. It can be used as a guideline for the design of a horizontal multi-layer porous wave absorber. 2022-03-07 11:11 am #1 2022-03-07 11:11 am #1Calculate Optimal Gap Size for Given Frequency. Porous Absorber Calculator. A ruff rule is the porous absorber should have at least the thickness of 1/3 of the wavelength you like to absorb. The ZORBA software is a tool for calculating the sound absorption coefficient of porous materials and perforated surfaces. So I've been researching my little butt off trying to figure outSo am I getting this right? I'm trying to shoot an 85Hz null in my studio. I'm willing to make it up to 0.