Air-backed porous absorber (i. But I think I have a much better understanding now, especially thanks to the Porous Absorber Calculator (the excel spreadsheet). But Basotect has a coefficient of 0,8 at about 800Hz while Sonorock reaches the same value at about 1,2kHz. Each layer can be either a porous absorbent or an air gap. The 2 inches of linacoustic material behind my false wall did wonders for the sound quality of the room! sirjaymz. Corner Bass Traps completely filled with Hemp (3000 rayls/m) and broadband panels 4-6" deep (maybe with membrane in the middle to prevent too much HF absorption) using an. Porous Absorber Calculator. m for pink fluffy, 8000-1000 for Safe and Sound, 16. Your. 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. But this, this is a problem beyond simple Excel. The air volume is partly or completely filled with mineral wool or foam. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. Speech Reinforcement CalculatorNote: I know that the results from Porous Absorber Calculator can't be fully applied to my design, because PAC assumes that slat width and spacing is always the same. [ie 5/6 of the original air filled case] There is no design formula that I have found that allows an accurate air/porous absorber mix to be considered. They only reflect high and mid. Acoust. 1. 5923%, respectively. Model: Allard & Champoux (1992) Absorber Parameters. 9 and its pore density. I've done the modelling in Pourous Absorber Calculator, Multi Layer. Hello again! I have some challenges in my room, and been reading up on alot of stuff. These briefly and simply cover the basics (and have lots of pictures ). g. 16,600 is OC703, 5000 is fluffy. I think I have read that ideally one shouldn't mix materials in broadband absorbers. 8 kg/m3 can be alternatives. The complete way for calculating this would be to feed the data into a finite elements simulation. Thickness of the template is 1/8” = 3,175 mm. Maybe density is somewhat correlated with GFR, but to my knowledge GFR, thickness and air gap is the only thing to consider when designing Bass Traps using porous materials. A porous absorber may have an absorbtion curve like this. A 2BA/multiBA setup will help. Porous Absorber Calculator - About. 1 Website for Pro Audio. It can be used as a guideline for the design of a horizontal multi-layer porous wave absorber. Absorption Area. 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. If you didn't download it yet grab this: Porous Absorber Calculator V1. Impedance prediction methods have been published by Delany and Bazley, Qunli, Miki, Mechel, Mechel and Vér, Komatsu, and Allard and Champoux. porous absorber calculators. This sheet shows two absorption curves for a single layer of porous absorber with and without an air gap. Play a little bit with different thickness and different Flow Resistivity you will see your self. Use diffrent angels because base resonances come from everywhere. . 8 1 Absorption Coefficient • 5000 mks rayls/m • 30000 mks rayls/mPorous Absorber Calculator V1. You can predict and play around with these matters using this online calculator Porous Absorber Calculator Gas Flow Resistivity numbers (related to but not the same as density) here Common Gas Flow Resistivity numbers. I constructed a ~100 mm thick absorber using rockwool (mineral fibers) and modeling shows it is effective down to low hundreds. New Porous Absorber Calculator. if the absorber is larger than the wavelength (for example, 1 kHz has a wavelength of 34 cm), we can already achieve good absorption with a single absorber. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. Most bass will be absorbed by the rear wall absorber anyway; I just want something that better than nothing in the front. Low densities seem good for broadband traps if thick enough. ) broadband absorbers. 5rayls/m) 1200mm Porous Absorbent, 1500 Pa. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. 2m porous absorber, 1. This gives an open area of 18%. With 40cm thickness, the 040 would actually be better without airgap according to the Porous Absorber Calculator. 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). 2 Glass wool as porous damping) towards the end is quite easy to understand. It is assumed that there is a rigid backing (such as a solid wall) behind the. 8 kg/m3 can be alternatives. what is your opinion about porous absorber calculators online such as: and. Energy Time Curve DIY Acoustic treatments. Not sure how big an absorber I'll need to reach 30hz (It may be an impossibly large box for me to build) but I think I can tackle the 55 hz one with some help. which could be applied to porous absorption with and without perforated facings3. g. The ZORBA software is a tool for calculating the sound absorption coefficient of porous materials and perforated surfaces. there are many, like cotton batts, fabric acoustic panels, and any porous. Some things were way off. s/m2 is a good bet. The Porous APorous Absorber Calculator Sent from my iPhone using Tapatalk. By exciting a room mode from 2 sources with opposing phase, the corresponding peak or dip in frequency response is reduced or removed entirely. Take a look at every anechoic chamber in the world. One or the other is a question of thickness, use the porous absorber calculator to decide what you want, based on your available room space and your needs to absorb the lower frequencies. 3°. The others perform atrociously, but even the Komatsu won't work correctly for mixing different densities. Personally, I think it's the better option. Hi All I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. If you want rear tuned absorption, build panel absorbers tuned to the lower range where the porous absorber is no longer effective. Numerous computational models to map the acoustic effectiveness of open-porous absorbers are available for your design, for example: empirical model of DELANY and. If an absorber is composed from multiple layers of porous materials or porous materials and airspaces, the absorption coefficient can be calculated using the transmission matrix method [3], [4], [5], [6]. 90 width you are lost in regards to bass if you rely on absorption only. Hey guys, I need broadband absorption down to 50Hz. It is particularly valuable in designing soundproofing and acoustic treatment solutions for various environments. Speech Reinforcement CalculatorThe damped walls are acting as membrane absorbers below that range, requiring an additional 30-45 cm air gap, to absorb down to 20 Hz. Helmholtz Absorber Calculator. Originally Posted by Kyle P. Maybe density is somewhat correlated with GFR, but to my knowledge GFR, thickness and air gap is the only thing to consider when designing Bass Traps using porous materials. Porous Absorber Calculator. This webpage is a reimplementation of the "Porous Absorber" sheet in the. The sound dissipation mechanism in MPPs is based on the principle of the Helmholtz resonator (HR) []. 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. 1. If you use lower GFR the Q is widened but damping is lowered. 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. 16000, 23400, 27000 (c/o NASA!). and the porous material layer was established by using Delany and Bazley’s model. Flow resistivity. Sound-absorbing performance of copy paper composites with bulk densities below 442. ZORBA is currently available in version v3. 2 0. It claims to be capable of calculating the absorption -coefficient for multilayer absorbers. /s/m2 (we don't know) (according to this porous absorption calculator) Porous Absorber Calculator On the other hand a Limp. hi guys trying to figure out which of these 2 products would be ideal for bass trapping. 1 (a) that comprises a cavity, neck, lids and porous material. So for porous absorber lower is good. Absorber thickness. That said, we get back to this question. Air gap 1. Sound is attenuated due to viscous friction in the submillimeter size pores. Is it possible to predict the behaviour of a porous absorber used as a gobo somewhere in the room?. Multi-layer absorbers composed of perforated plates, airspaces or porous materials are used widely to absorb broadband noise [1], [2]. Given frequency : Hz. Perforated Panel. It is assumed that there is a rigid backing (such as a solid wall) behind the. Unless care is taken when deciding on the size of the absorber unit, these holes will not add up. Porous materials are the most commonly used absorbers. If you change the vibrating mass and stiffness of the. 2)12 inch of Roxul Safe N Sound Floor to ceiling. concepts, models, and algorithms developed for porous media in the geosciences are not directly applicable and there is a very strong need for tailored models. A Porous Absorber Calculator is a specialized tool used in acoustics and engineering to determine the acoustic absorption characteristics of porous materials. . I was making porous absorber calculations on a multilayer absorber calculator. A higher fiber density leads to a more complex path inside the porous absorber therefore it implies higher interaction between sound waves and fibers. See below for approximations of absorption coefficients for the theoretical 21" thick R38 (blue line, absorber 1) and the 1. The actual average sound absorption coefficient of the microperforated panel + cavity + porous metal + cavity sound absorber in the 100–1800 Hz range reached 62. You can space the panels off the wall as you wish, there is no problem with what you want to do. Even if it's peaked in planned location, most probably you'll have to measure and investigate to see results. 10th June 2011 | Show parent #19. Multiphysics couplings are essential to capture the effects of porous media on transport processes. Here is probably a good place to promote this relatively new Porous Absorption Calculator, thanks to Demetris. perforated wood over acoustic foam porous absorbers. 5" rockwool on the wall (green line, absorber 2,. 5m thick. s/m2 for OC703 (Please let me know if these are incorrect). Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. It doesn't perform as a whole system with a cavity (which isn't sealed), it's rather a velocity based absorber which. 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. com - View Single Post - Room treatment advice and help interpreting GIK's published lab results Post 16047038 -Forum for professional and amateur recording engineers to share techniques. And unlike porous traps which work better. Example of a 10cm porous absorber. Is it possible to predict the behaviour of a porous absorber used as a gobo somewhere in the room?. 5k for OC703 (ignoring the NASA vs. 8 1 Absorption Coefficient. Agreement to Terms of Use This website is offered to you by acousticmodelling. From the first formula we can calculate specific airflow resistance simply by multiplying airflow resistivity [Pas/m2] with thickness of the porous material [m]. 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 is the link to the Porous Absorber Calculator. All the source code for this app is availble on my Github repo "porous_absorber". All the source code for this app is availble on my Github repo "porous_absorber". The No. Absorption coefficient measurements are not easy, where materials are placed and having no regard of their shape or extension. . Which one would you place closer to the wall when building a porous. I'm building a 300mm deep bass trap at the front of my room and have played with the calculator at Porous Absorber Calculator and RWA45 seems to best suit my needs. 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. See here: Porous Absorber Calculator. Resonant absorbers are further divided into panel absorbers and Helmholtz resonators. Absorber Parameters. Since membrane absorbers require high level of precision to perform at the desired frequency, they are often customized for a specific application. Being made from organic stuff means nothing. (broadband) the glasswool Quietel is 130kg/m^3, comes in 2400*1200*25mm sheets and costs $33. Predict material properties, surface impedance and absorption coefficients of acoustic absorbers. 5°, and between the (Flat plate and metal foam 40 PPI) absorber plate was 8. Some carefully placed spacers (smaller strips of insulation) could keep it off the wall. The calculator is easy to use just make sure to select "Komatsu (2008)" for the porous model on the left side of the page. 59 You can see by messing with the GFR numbers that unfortunately a higher GFR material (estimates for ultratouch are around 15-20k/rayls?) will work well above 100hz at lesser depths, at the expense of being less effective below. ZORBA is currently available in version v3. The curve changes a bit as I vary the air flow resistivity (I'm using roughly. I am interested in porous absorption of low frequencies since it is. placed in the middle of the room. I'm playing around with porous absorber calculator and trying to find a good balance between effective and practical. ( 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 app is designed to assist acousticians when designing environments such as home cinemas. Calculates the absorption curve of various porous absorber systems. Often porous materials with spherical grains have lower porosity than materials composed of non-spherical grain. 2 coefficient at 50 Hz (about 0. Quite a bit of comb filtering in there but. A reset button is provided which returns all global parameters (and parameter options) to their default values. Toyoda, E. Carpet on the floor and broadband absorbers covering most of the ceiling. Punching in those numbers, expect . 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. After plugging those numbers into a porous absorber calculator, I suspect the wool would perform better at greater thicknesses, e. 8 1 Absorption Coefficient • 100mm 5K • 50mm 5K, 50mm 16K • 50mm 5k, 60mm 16K, Perf PanelMicroperforated panels (MPP) are acoustic absorbers that are reclaimable, noncombustible, and environmentally friendly. Microperforated Panel. Served on a. Hi! I have an example, and I'd like to know if it I possible to do the math here. The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. not easy but it's doable. no backing) For the air-backed absorber geometry, Strutt also allows the calculation of the transmission loss through the porous material. Porous absorbers, as the name would suggest, are made from a multitude of tiny holes – cells, through which sound travels. 2022-03-07 11:11 am #1 2022-03-07 11:11 am #1Calculate Optimal Gap Size for Given Frequency. (18), (19)) are used to calculate the Nusselt number and the Darcy-Weisbach friction factor, respectively [46, 47]. I decided to prepare perforated panel with porous absorber. s/m2, a 2ft thick absorber can be 70% effective at 50Hz. 69%, which was superior to that 25. (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. Parameters Global Parameters Air temperature: 20°C Air pressure: 101325 Pa X Axis: Frequency Range: 20Hz - 10000Hz Scale: logarithmic Resolution: medium Angle of incidence: 0° Porous model: Komatsu (2008) Helmholtz model: Ingard/Allard Absorber Parameters • Absorber 1 20mm Slotted Panel, 10mm/80mm (12. DSP like a DCX2496 is cheap and with placement and experimentation and treatment you can achieve a lot. You can play with the porous absorber calculator to find suitable dimensions. The proposed sound absorber design is an evolution of the two-segment SeMSA design to a more complex multi-sector design. 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. . You don't need breathable cloth for bass traps. 2. Some online calculators as well as commercial software are also available for absorption calculation. Predict material properties, surface impedance and absorption coefficients of acoustic absorbers. Tortuosity was essential a capacitance test with a wetted material. 8 1 Absorption Coefficient • bass trap1 • bass trap2 • side panel • back panelMembrane absorbers work best with lower-frequency and bass frequencies. plastic membranes or 2. A resonant absorber is a vibrational system that “runs” on sound pressure. Since a porous absorber, also called a velocity based absorber, works by slowing down air particles, that means that it is less effective the lower the particle velocity is. Share Reply Quote. My Studio. So attempts to calculate or predict absorption using a calculator based on a single depth are futile. s/m2 Layer 4: not used (Rigid backing) Using the Allard & Champoux model for porous absorbers (which should be the most accurate from what I’ve read in several articles) I got a result that showed me an absorption coefficient of over When set to "Absorber", the model can be set individually for each absorber. s/m2, a 2ft thick absorber can be 70% effective at 50Hz. 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,. Tuned pressure absorbers work only if pressure at tuning frequency is present, they will not work i. The flow resistivity of the layer in Pa. 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. this formula or e. com, are committed to protecting and respecting your privacy and take this very seriously. These Website Terms of Use apply to the entire contents of this website under the. When set to "Absorber", the model can be set individually for each absorber. "f" is frequency (50 Hz in this case), "σ" is flow resistance. 70% of original porous metal absorber and that 31. Username: Password: Forgotten password? Register home | terms of use | privacy policy | links | contact: Copyright. 6 0. ReplyThe No. 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. Porous Absorber Calculator. According to the Porous Absorber Calculator this should give good absorption down to at least 50hz (and probably lower). June 21, 2019. A microperforated panel absorber may have an absorbtion curve like this. Either one wants low GFR and doesn't compress, or compress as a way to emulate the higher GFR of OC 703. a superchunk) it is better to use insulation with a lower gas flow resistivity. PaulRain. 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. 58 (RPG´s BAD template is 600x600 mm with 512 holes, each Ø12,7 mm. Multi-layer Absorber Calculator 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. Users with access to the relevant academic papers. If you drop down to about 4K Pa. Porous Absorber Calculator Preamble. "Absorber 3" would be the side walls, mostly starting at hip height and touching the ceiling. Σχετικά με το Porous Absorber Calculator (Formula) Ο υπολογιστής απορρόφησης πορώδους είναι ένα εξειδικευμένο εργαλείο που χρησιμοποιείται στην ακουστική και τη μηχανική για τον προσδιορισμό των χαρακτηριστικών ακουστικής. 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. I would look into tuned devices. Agreement to Terms of Use This website is offered to you by acousticmodelling. 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. 6m walls, there is a 2. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. com not registered yet? I also played around with the porous absorber calculator, but in the past, real life measurements did not shine a good light on this calculator. The problem is, I'm not seeing results that confirm the general wisdom -- that. s/m 2. Flow resistivity. 8 1 Absorption Coefficient • 1. Oh well, experimentally bruteforcing it. Documentation. m Shows how the open area changes the surface impedance and absorption coefficient of some Helmholtz. Close inspection reveals that the metal foam absorber plate is cooler than the. The distance in mm between the porous absorbent. 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. If a different material such as rockwool or cotton or hemp fiber boards are used to make a porous absorber, you must ignore the density properties of 703 [3 lbs. 6 0. The resonant frequency could be calculated using e. If you only record singing, there is no need to worry about sub 100 hz frequencies. First Reflection Calculators Wavelength - Frequency Calculator Calculate Room Modes Calculate optimal Room Dimension Reverb (RT60) Calculator The Wall Behind The Loudspeaker Absorbers Helmholtz. This app is designed to assist acousticians when designing environments such as home cinemas. Joined Nov 15, 2020 Messages 7,363 Likes 7,810 Location Brussels,. Up to four absorbers can be modelled at once, each of which can have up to four layers. I used theIve been experimenting with the Porous Absorber Calculator V1. Which one would you place closer to the wall when building a porous absorber ? Porous Absorber Calculator. 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. It will let you model various combinations of panel width, air gap, and material type. Multi-layer Absorber Calculator. If the cavity is filled with porous absorbent, then the system is no longer adiabatic, and an isothermal case should be considered. The flow resistivity of the porous absorbent in Pa. The porous absorber calculator does not offer a complete solution for diagonal traps. Absorber Parameters This calculator estimates the absorption coefficient of a porous aborbent covered with a perforated panel. 2 Glasull som porös dämpning" (B1. 7 and 1 kg/m²) and would. not registered yet? join now! login: join with facebook. Look up the Porous Absorber Calculator and you can see the graphs for yourself. Mike Rosinski P. 1 (b) is porous. 1. Porous Absorber Calculator. 300 - 4500 Hz. 16000, 23400, 27000 (c/o NASA!). I can't for the life of me figure out why and I'm pretty damn sure I can't for. This is a reference guide for basic acoustics and room treatment. Absorber ParametersHi I just wanted to share an alternative design for absorbers that i made in my listening room. Behind the template is glass fibre filling with density 6-8 lbs/ft³ (96-128. s/m2 There seem to be a few available on the web for common insulation materials like Rockwool but you need to hunt around for them. Porous Absorber Calculator Last edited: Oct 18, 2021. 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. Glass wool fibers have poor deformation and decreased sound absorption in the. 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. All formulas and units are the same in NASA. But in my design, the open area will also be roughly 50%, so I figured the results would be useful anyway. The absorber calculator tells me diffrent (pic below). Multiphysics couplings are essential to capture the effects of porous media on transport processes. you may not need to be terribly concerned with the. 6 as significant) absorption at and above 60 Hz with your design. Wherein, there is a cylindrical porous absorber which is sealed behind a quartz window. Calculates the absorption curve of various porous absorber systems. 16 @ 125Hz, 0. 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. 2 times the material thickness. Absorption Area. The absorption is very dependent on the type of carpet and how it is made. The lowest room mode you have between your ceiling and floor is at 75 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. 1. Perforated Panel. These calculators may not be very accurate, especially for more complex scenarios such as mixing materials. Porous Absorber Calculator. For fibreglass enter 16816. Username: Password: Forgotten password? Register: Calculator. 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. Consult with the handy "Porous Absorber Calculator" to predict your planing for a the device which won't result in a narrow band device but more of a natural low pass filter- Large perforation area+large diameter holes. now I get different results on calculations, which are more realistic. how to predict the behaviour of a Gobo - Gearspace. The sandwich acoustic structure. 5αCL/A (C is the circumference, L the length, and A the cross‐sectional area of the absorbing duct). Porous Absorber Calculator V1. What I wanna try is to build something like this:. When sound propagates in small spaces, such as the interconnected pores of a porous absorber, it loses energy. The mass is the cabinet and front wall or diaphragm. Air gap 2. The porosity of copper foam is 0. Guest. Someone smarter than me can probably elaborate further. 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. If you download and play with the porous absorber calculator: Porous Absorber Calculator V1. It is generally better to fill the space keeping it about 1/2″ away from the perforated panel. this online calculator b) A bass or broadband absorber using porous material with a perforated plate or slats in front which is a different system. The prediction of the sound absorption coefficient in diffuse field conditions is of great interest to an acoustic project. Since a porous absorber, also called a velocity based absorber, works by slowing down air particles, that means that it is less effective the lower the particle velocity is. 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. Business, Economics, and Finance. Yeah, for porous absorbers, lower GFR is better for LF absorbtion, but the thicker the trap needs to be. Global Parameters: Air temperature °C. Let us take a look at a plane sound wave vertically incident on a rigid wall. 52 and download the Porous absorber calculator. 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. Do you think I can rely on improved insulation in the sub area if I order the 045 Caruso (400mm) and use an airgap? Only with this airgap I would have a much better effect in the sub range. 2. A ruff rule is the porous absorber should have at least the thickness of 1/3 of the wavelength you like to absorb. The sound absorption capabilities become broader and it covers a wider frequency bands. Reply. Flow resistivity is related to density. 8" or more. 49% of the microperforated spring steel panel absorber. Porous Absorber Calculator V1.