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. It doesn't perform as a whole system with a cavity (which isn't sealed), it's rather a velocity based absorber which. Most importantly, these results should match those in the papers written by the people who developed the models. m −2 and thickness h = 150 mm. 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). Helmholtz Absorber Calculator. To be honest, real life testing is the only to be sure. This app is designed to assist acousticians when designing environments such as home cinemas. s/m 2. The lowest room mode you have between your ceiling and floor is at 75 Hz. Diaphragmatic absorbers are good for going after frequencies below 90 Hz. V-corrugated absorbers have been. Porous absorbers are most effective with mid to treble tones. not registered yet? join now! login: join with facebook. Gear Guru . Dammit, is it so difficult do download the bloody thing and insert some bloody numbers? OK, here are some values as being written in my secret documents (no actually derived from Porous Absorber Calculator, hehe) for 48 Hz. You can confirm what I have said using a porous absorber calculator which is available online. First of all, I came across the Porous Absorber Calculator by Chris Whealy. where: \alpha_m αm - The average sound absorption coefficient; 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. This is primarily due to viscous boundary layer effects. This gives an open area of 18%. com. This only works with absorbers of uniform thickness and triangular bass traps obviously have varying thickness. A thought occured regarding the tuning of these panels. How does one calculate or predict a perforated panel with porous absorber when the shape is. 064–0. Sound-absorbing performance of copy paper composites with bulk densities below 442. Rigid backing. The mass is the cabinet and front wall or diaphragm. Tortuosity is a measure of path length within the material. Multiphysics couplings are essential to capture the effects of porous media on transport processes. 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. Now you can determine which absorption you can expect from what you have. g. 4 kg/m3 and corrugated board composites with densities of less than 474. To enhance the performance of porous absorbers, incorporating an airgap behind them proves to be quite effective. For thicker absorbers and irregular slat sequences measurements are needed. On the other hand, Chris Porous Absorber Calculator actually shows that for the low. The diameter of each hole in mm (perforated panel). The resonant frequency could be calculated using e. The nice absorber calculator you posted only confirms: 10cm is useless under 100Hz, 20cm does very little and more is physically impossible. Application areas range from micromechanical devices to seismic wave propagation. Place the cloth against the wall though, and you'll have a hard time. The lowest room mode you have between your ceiling and floor is at 75 Hz. Each layer can be either a porous absorbent or an air gap. Wherein, there is a cylindrical porous absorber which is sealed behind a quartz window. So the true effective depth for a gapped porous absorber is more than 1. 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. 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. When sound propagates in small spaces, such as the interconnected pores of a porous absorber, it loses energy. 1 Website for Pro Audio. 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. They are usable with. Multi-layer Absorber Calculator. They all absorb sound energy as they damp the oscillation of the air particles by friction. 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. 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. Of course I won’t know for sure until I get my hands on the stuff and build some absorbers (at which point I’ll be happy to share my results). Leave a Reply Cancel Reply. It calculates the acoustic. 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 decided to prepare perforated panel with porous absorber. Personally, I would figure out which materials are available in your area first and then start modeling. 35 absorbtion at 30Hz and increase to 0. Is this a good way to deal with modal issues? 2. It is not impossible to get a theoretical efficiency of 0,5 at 30Hz with porous absorption, if you use a combination of. com. The spring is the air inside the cavity of the resonant absorber. Rigid Backed Porous Absorber. Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. 65 at 100Hz for an average of 0. Gushue ️. Reply. 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. Yeah, for porous absorbers, lower GFR is better for LF absorbtion, but the thicker the trap needs to be. Termination of such 'gaps' is clearly not mandatory. A comparison study Oliva and Hongisto (2013) concluded that Allard and Champoux's model (Allard and Champoux, 1992) is the. Delany and Bazley. Mounting and. Applying a mass-flow ( ρ 0 S e j u j ) excitation on surface nodes as a system input, it is possible to solve the problem and calculate the pressure. 55 Normal fluffy is about 5000 rayls/m with denser fibreboard around 15000-25000. Perforated Panel. The spring is the air inside the cavity of the resonant absorber. . CryptoApplication of Porous Metals. no backing) For the air-backed absorber geometry, Strutt also allows the calculation of the transmission loss through the porous material. The equation is modified to f=50/sq root(1/md). 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. This membrane effect is "tuned" to a specific frequency depending on the density and thickness of the material. not easy but it's doable. 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. Obviously I'd need more surface area to make a real dent in a room that size. 16000, 23400, 27000 (c/o NASA!). Acoustic plate absorbers have NRC ratings of 0. 3 to 2 kg/m² (most probably between 0. e. 2. Either one wants low GFR and doesn't compress, or compress as a way to emulate the higher GFR of OC 703. you may not need to be terribly concerned with the. 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. Hey Guys, I wanted to try a few calculations of membrane absorbers to see how the different air and absorber depths affected the absorbers. . This is primarily due to viscous boundary layer effects. 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. 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. Sound absorption materials also need to have great loss of sound energy, air permeability, and refractory quality, as well as the required level of structural strength [40]. All the source code for this app is availble on my Github repo "porous_absorber". 2)12 inch of Roxul Safe N Sound Floor to ceiling. When I use the Porous Absorber Calculator, it shows these to be fairly similar in performance. When set to "Absorber", the model can be set individually for each absorber. This is due to the fact that the air resonance in the airgap and porous material layer is further damped by the porous material layer. First Reflection Calculators Wavelength - Frequency Calculator Calculate Room Modes Calculate optimal Room Dimension Reverb (RT60) Calculator The Wall Behind The Loudspeaker Absorbers Helmholtz. 8" or more. Liu, G. Multi-layer Absorber Calculator. I was making porous absorber calculations on a multilayer absorber calculator. Being made from organic stuff means nothing. • Absorber 1 (1. Having that much depth allows me to absorb lower but it creates. Calculates the absorption curve of various porous absorber systems. a superchunk) it is better to use insulation with a lower gas flow resistivity. The air gap behind the absorbing material will effectively act as if the absorber would go all the way to the wall. . Take a look at every anechoic chamber in the world. (notice the. The formula is: \alpha_m = A / S αm = A/S. Served on a. Whether you're just getting started or want some touching up, this should be a good place to start. Porous Absorber Calculator. Try this calculator: Porous Absorber Calculator Generally, the thinner the absorber, the higher the resistivity needs to be. Then I. We considered the zoy plane where the center of the tube is located as the cross-section, and obtain the cross-section of the absorber, as shown in Fig. how to predict the behaviour of a Gobo - Gearspace. 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. My questions are: 1. no backing) For the air-backed absorber geometry, Strutt also allows the calculation of the transmission loss through the porous material. A Porous Absorber Calculator is a specialized tool used in acoustics and engineering to determine the acoustic absorption characteristics of porous materials. 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. 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. Global Parameters affect all absorbers. Sound is attenuated due to viscous friction in the submillimeter size pores. I thought tri (superchunk) style absorbers were good for low frequencies mainly? Quote: Originally Posted by avare As practical proof, consider how often people have. Porous Absorber Calculator Preamble. The calculation doesn't assume a sealed cavity, except for a resonator. Results. Much ore than that (~200mm+) makes them even better at lower freq. If you can find the Gas Flow Resistivity of the product you could predict the absorption spectrum using this calculator. The air volume is partly or completely filled with mineral wool or foam. Multi-layer Absorber Calculator. If you download and play with the porous absorber calculator: Porous Absorber Calculator V1. The setup follows international standards with about 10 m² of slat absorber in an echo chamber. You will fast get a feeling which absorber thicknes is the next one to build. 5th August 2017 #5. Absorptive treatment such as mineral wool, glass fiber or high-porosity foams reduces reflection sound. 0 with a German user interface and is developed by Marshall Day Acoustics. I am using this link Porous Absorber Calculator and using a rockwool product with a 70kg/m3 density and around 30kPa. I am quite a noob but i’ve been researching a lot about it the past few weeks. Improved sound absorption performance of three-dimensional MPP space sound absorbers by filling with porous materials. 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. Using the porous absorber tube causes the surface temperature to decrease. Thank you Can you help me clarify the difference between "random incidence" and "normal incidence" options in the porous absorber calculator? Share Reply Quote. 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. 8 & you will see the LF absorption. Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. I've been building my own panels using Rockwool as the absorber. Absorption Area. My Studio. The porous absorber calculator says 'yes' when I plug in a GFR of 2500. My comment is. Your. then throw it into the porous absorber calculator and compare it to OC703. Porous Absorber Calculator You could try to have your dividing wall resonate damply LOL below that to even more and better LF absorption. Dennis Foley says: May 4, 2023 at 5:10 pm. If you know any other quality tools, please tell me! List of other quality acoustic calculators besides amcoustics. 080, and its porosity (P 1) 0. The distance between the holes (centre to centre) in mm (perforated panel). 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. See here for a simple porous absorber calculator. An example of temperature distribution over a part of the StepRec module without air movement through the receiver is shown on Fig. 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. Adding an air gap between the. Caruso absorber panels are one of the most economic and efficient acoustic treatments. There is also a loss in momentum due to. 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. Often porous materials with spherical grains have lower porosity than materials composed of non-spherical grain. Originally Posted by Kyle P. Air-backed porous absorber (i. -Assume you have a 12 dB peak at 100Hz that you want to treat. Helmholtz Absorber Calculator. The normal incidence sound absorption coefficient of porous materials can be predicted when the specific acoustic impedance of the material is known. Porous Absorber Calculator I haven't seen great performance from the 24 inch SSC's, while the 34 inch ones rock. To estimate the attenuation D of silencers under practical conditions, the formula of Piening is used: D=1. Share Reply Quote. Slotted Panel. Presenting high surface areas to the incident sound wave provides rapid absorption of the wavefront. Porous Absorber Calculator. Microperforated Panel. Otherwise your just making another reflection point. 9 and its pore density. I know I’ve linked this elsewhere, but I think it’s a valuable tool which is worth repeating. Hello ! First post but i'm reading for years Thank to everybody who shares so much great info ! ( Thomas Northward, Boggy, GE, Jens E. this formula or e. 16 @ 125Hz, 0. 2m porous absorber, 1. Thermohanf porous absorbers. Can these be converted to Flow resistivity Pa*s/m2 ? (to be used in porous absorber calculator) Share Reply Quote. I was planning to buy the Bradford Fibretex 350 - 60kg/m3 batts (3 for $128 - 100mm thick 1200mmx 600mm). Chen, in Porous Materials, 2014 3. 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. Flow resistivity is measured with DC pressure loss. 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. 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. Absorber Parameters: Layer: This field sets the type of layer as follows: Not used; Air; Porous absorbent; Limp membrane; Perforated panel; Thickness: The thickness of the layer in mm. Numerous computational models to map the acoustic effectiveness of open-porous absorbers are available for your design, for example: empirical model of DELANY and. Porous absorbers. There is the amacoustics calculator that works for helmontz and other types of perforated and membrane panels before the absorber. Punching in those numbers, expect . Thread starter celef; Start date 2022-03-07 11:11 am; Jump to Latest celef. As I plan to absorb also VLF at around 40 Hz I like to achieve this with very deep porous absorbers (500-1200mm). 2m porous absorber,. Joined 2012. The unit cell is a cube with sides equal to 2r where r is the radius of sphere. 35 per sq metre here are some specs for the products. Flow resistivity is related to density. The distance in mm between the perforated panel and the porous absorbent. Porous silicon carbide (SiC) is widely used as the absorber due to its high-conductivity, high-absorption, and anti-oxidation [12]. 8 1 Absorption Coefficient. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. The thickness of lids is 1 mm. They have specifiable one-third-octave- center band frequencies between 40 and 100Hz. When paired with a porous acoustic core, they present a wider more linear absorption coefficient, making them a preferred option. 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. Porous Absorber Calculator - Results According to the calculator, you will still get significant (I consider anything over . Luca, You don't say whether you want corner bass traps, membrane absorbers or Helmholtz resonators. Porous Absorber Calculator - About. Gear Addict . The work deals with individual parameters such as the size of the air gap; membrane absorber thickness; its density, flexibility, and, in particular, air flow resistance. s/m2, a 2ft thick absorber can be 70% effective at 50Hz. Gearspace. The composite sound absorber includes a MPP (micro-perforated panel) layer, a porous material layer, and an air cavity layer. I'm not sure on the gas flow resistance of Safe n Sound (hopefully Andre can pop in with a number tomorrow) but if its anywhere near pink fluffy, the result difference would be this: Porous Absorber Calculator - Results Now this is assuming a rigid boundary and is not taking the corner into account, but still, the difference isn't negligible. Introducing an air gap behind the porous absorber is a simple and cost-effective technique to enhance sound absorption at low frequencies. but do consider the reality it's a little bit better than the plot because the calculator considers only a single angle of incidence. I constructed a ~100 mm thick absorber using rockwool (mineral fibers) and modeling shows it is effective down to low hundreds. To calculate the effective coefficient of thermal conductivity of porous absorbers, the simulation was carried out without air movement inside. 5°, and between the (Flat plate and metal foam 40 PPI) absorber plate was 8. porous absorber calculators. 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. Its value ranges from 0 to 1, with 1 being the perfect absorber. Multi-layer Absorber Calculator 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. AdamIf you have 28 inches, less 17 for the speakers, less 6 inches from the speakers to the AT screen that leaves 11 inches. A higher fiber density leads to a more complex path inside the porous absorber therefore it implies higher interaction between sound waves and fibers. 0. E. Share Reply Quote. June 21, 2019. - Room modes calculator home | terms of use | privacy policy | links | contact: Copyright © acousticmodelling. Hi! I have an example, and I'd like to know if it I possible to do the math here. 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. They call it "k" but I'll call it Kp for clarity. Model: Allard & Champoux (1992) Absorber Parameters. If you utilize an air gap behind the panels it will increase absorption in the low mids. Let's call C p the speed of sound in the porous absorber. 300 - 4500 Hz. . A good thing to look at relative to bb absorbers and GFR is the porus absorber caluculator: Porous Absorber Calculator V1. Some things were way off. 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. 59 There are also some interesting studies from the BBC and NASA which support this approach. For most of the porous absorbers the absorption coefficient α can be estimated by the very simple relation α=0. The Whealey porous absorber calculator tells you all: Number one, make them thick, number two alternatively use an air gap, number three, don't make them too dense (see my posts in the link above for a rough understanding of that). Much ore than that (~200mm+) makes them even better at. 's most successful trap, after many many attempts, was a panel one. ↑ top; home; New Product Alert; classifieds; reviews; deal zoneAt high frequencies, i. 16000, 23400, 27000 (c/o NASA!). Ye Old Porous Absorber Calculator. Each 6x3 roll of BassBloc™ Bass Absorber covers an area of 18 sqft : BEST FOR SOUND AND BASS ABSORPTION: BassBloc™ Bass Absorber Acoustic Foam. Behind the template is glass fibre filling with density 6-8 lbs/ft³ (96-128. Parameters Global Parameters Air temperature: 20°C Air pressure: 101325 Pa X Axis: Frequency Range: 20Hz - 10000Hz Scale: logarithmic Resolution: medium Angle of. Here's the link: Porous Absorber Calculator. Porous Absorber Calculator 4" mineral wool is actually 3. Whealy C. Helmholtz Absorber Calculator. s/m2. Multi-layer Absorber Calculator. com 2011. m −2 , thickness h = 50 mm, and cavity depth. They can be made from a variety of materials such as: acoustic foam fiberglass (glass wool) rockwool (mineral wool) And they’re extremely effective at taming common problems such as: room modes standing waves. The idea behind the "4 inch rockwool is only effective above 850 Hz" is that because porous absorbers work on sound velocity, and particle velocity is zero close to a rigid wall, for maximum efficiency an absorber needs to be placed at least at 1/4 wavelength. For example, the angle of incidence can be set as a global parameter. Calculates the absorption curve of various porous absorber systems. Close inspection reveals that the metal foam absorber plate is cooler than the. Actually it doesn't. 8 1 Absorption Coefficient • bass trap1 • bass trap2 • side panel • back panelMembrane absorbers work best with lower-frequency and bass frequencies. Global Parameters affect all absorbers. Solving for C p gives us: C p = (C 0 *K 0) / (K p ). The rotational speed of the bed varied from 150 rpm to 1500 rpm, and the gas flow rate ranged from 20 m 3 h-1 to 60 m 3. I'm not sure on the gas flow resistance of Safe n Sound (hopefully Andre can pop in with a number tomorrow) but if its anywhere near pink fluffy, the result difference would be this: Porous Absorber Calculator - Results Now this is assuming a rigid boundary and is not taking the corner into account, but still, the difference isn't negligible. This app is designed to assist acousticians when designing environments such as home cinemas. Air gap 1. Air gap 1. 1 Website for Pro Audio ; The No. . 5αCL/A (C is the circumference, L the length, and A the. P. the direct path angle/evctor is irrelevant. online calculators for porous absorbers. Modeling the Damping Effect. e. Porous Absorber Calculator - About. The temperature profile is also shown in longitudinal direction in different angles for the configuration VI and the non-porous state in this igure. 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. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. The same porous absorber calculator can model multi layer, limp mass and helmholtz traps - just click the calculator icon to see a drop down to select Off topic - but I'm constantly amazed and impressed with the quality of the audio tools that developers provide for free on the internet such as this one, REW, HornResp, QRDude, Multi Sub. It will let you model various combinations of panel width, air gap, and material type. Layer 3: 240mm porous absorbent, 5000 Pa. IMO perfect tuned absorber it's a "virtual hole" for sound wave with a given frequency. But in my design, the open area will also be roughly 50%, so I figured the results would be useful anyway. Here is probably a good place to promote this relatively new Porous Absorption Calculator, thanks to Demetris. Porous Absorber Calculator. Hi all, I have a (at the moment) theoretical question for the experts here: If one wants to try and control frequencies as low as possible in a room, iSound absorbers can be made from porous materials or resonant structures, and the main mechanisms for sound absorption are acoustic impedance matching on the absorbers’ boundary and acoustic. Parameter Options determine whether certain parameters appear in the Global or Absorber sections. There is also a loss in momentum due to. The absorber is assumed to be in front of a. 2 Glass wool as porous damping) towards the end is quite easy to understand. 2 times the material thickness. . Have a play with this: Porous Absorber Calculator V1. 4 Applications. 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. However, not many published measurement results can be found. Trouble is, the only place to get it in NI is a 100 mile round trip, which I would need to do twice! A local supplier can supply rockwool cavity slab, but rockwool don't have gas. For sure. 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. 100mm Porous Absorbent, 10000 Pa. Absorber thickness. Porous absorbers are materials where sound propagation occurs in a network of interconnected pores (open pore structure) in such a way that viscous and thermal effects cause acoustic energy to be dissipated. 5th August 2017 #5. 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. 50%) 400mm Porous Absorbent, 4000 Pa. Being a porous absorbent, carpet produces mid– and high–frequency absorption. The ZORBA software is a tool for calculating the sound absorption coefficient of porous materials and perforated surfaces. We can ignore the imaginary term in the equation. Documentation. Solution. Long story short, when you have two materials, lets say one has 6kPa/m2 and another wit 12kPa/m2. com, are committed to protecting and respecting your privacy and take this very seriously. 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. . The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. plastic membranes or 2. On a microscopic scale, sound propagation in porous materials is generally difficult to study because of the complicated geometries of the frames. However, for basic calculations relating to multi-layer porous absorbers, both calculators should give almost identical results (provided the extra options in Soundflow. Porous absorber I already have and it is not enough for my frequency. The sound dissipation mechanism in MPPs is based on the principle of the Helmholtz resonator (HR) []. For example, I want to absorb. 2m depth in my calculations is only for hangers. 2 0. Helmholtz Absorber Calculator. Example of a 10cm porous absorber. See below for approximations of absorption coefficients for the theoretical 21" thick R38 (blue line, absorber 1) and the 1. Rigid backing. 4 0. Porous Absorber Calculator. 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. Porous Absorber Calculator.