. Yeah, for porous absorbers, lower GFR is better for LF absorbtion, but the thicker the trap needs to be. The. Reply. 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. The prediction of the sound absorption coefficient in diffuse field conditions is of great interest to an acoustic project. Resonant absorbers are further divided into panel absorbers and Helmholtz resonators. IMO perfect tuned absorber it's a "virtual hole" for sound wave with a given frequency. Porous materials are the most commonly used absorbers. This calculator estimates the absorption coefficients of multi layer porous aborbers. Agreement to Terms of Use This website is offered to you by acousticmodelling. The proposed sound absorber design is an evolution of the two-segment SeMSA design to a more complex multi-sector design. which could be applied to porous absorption with and without perforated facings3. 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. Maybe with tuned absorbers or perforated panels, but there are others here that have more experience with that. A 2BA/multiBA setup will help. 7 and 1 kg/m²) and would. 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. i think that most isolation material or foam benefit from stacking in depth and make bass trap from it. Take a look at every anechoic chamber in the world. If you utilize an air gap behind the panels it will increase absorption in the low mids. Tuned pressure absorbers work only if pressure at tuning frequency is present, they will not work i. with a lot of air behind them, like about 1,2m. Sound-absorbing performance of copy paper composites with bulk densities below 442. Dotted lines indicate that the model used to estimate absorber properties has been used outside of its applicable range. com. Share Reply Quote. m −2 and thickness h = 150 mm. There is also a loss in momentum due to. Guest. 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. Similar to the resonant panel they take up less depth than porous absorbers for a given frequency. But Basotect has a coefficient of 0,8 at about 800Hz while Sonorock reaches the same value at about 1,2kHz. com. 5 @ 500Hz, and 0. Using the porous absorber tube causes the surface temperature to decrease. If you blow air through a cloth it gets warm by friction; air flow turns into heat. The resonant frequency could be calculated using e. Welcome to room acoustics, where good sound quality goes to die. e. AdamIf you have 28 inches, less 17 for the speakers, less 6 inches from the speakers to the AT screen that leaves 11 inches. So, when guys like me and the OVERWHELMING MAJORITY of people on these forums who are looking for acoustic. 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. "f" is frequency (50 Hz in this case), "σ" is flow resistance. New Porous Absorber Calculator. Flow resistivity is related to density. 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. The distance between the holes (centre to centre) in mm. The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. Gear Guru . See here: Porous Absorber Calculator. "ω" is angular frequency, which is defined as 2*pi*f. For sure. 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. Perforated absorbers are lighter in weight than diaphragmatic absorbers and are for absorbing in the low middle. Multi-layer Absorber Calculator. feet. How does one calculate or predict a perforated panel with porous absorber when the shape is. Average sound absorption coefficient formula. The mass is the cabinet and front wall or diaphragm. . Porous Absorber Calculator You could try to have your dividing wall resonate damply LOL below that to even more and better LF absorption. Membrane resonators can be calculated with the Excel Spreadsheet Porous Absorber Calculator V1. My Studio. Caruso absorber panels are one of the most economic and efficient acoustic treatments. Have a play with this: Porous Absorber Calculator V1. s Owens corning 703, Rockboard AFB (or equivalent) - 16,000 pa. 1) why do my. Abstract. 55 at 125 Hz for. now I get different results on calculations, which are more realistic. there are many, like cotton batts, fabric acoustic panels, and any porous. 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. s/m 2 Porous Absorber Calculator. . The thickness of the porous absorbent in mm. 4 0. Flow resistivity. Layer 3: 240mm porous absorbent, 5000 Pa. absorption offered by the 3887rayls/m. If its. online calculators for porous absorbers. I think I have read that ideally one shouldn't mix materials in broadband absorbers. I know I’ve linked this elsewhere, but I think it’s a valuable tool which is worth repeating. Porous Absorber Calculator 2) the filtered impulse response at -60 dB or the topt can give an indication. The sandwich acoustic structure consists of an air cavity layer in between two MPP layers, which. IMO perfect tuned absorber it's a "virtual hole" for sound wave with a given frequency. Personally, I think it's the better option. This is primarily due to viscous boundary layer effects. m −2 , thickness h = 50 mm, and cavity depth. . what is your opinion about porous absorber calculators online such as: and. All in all, you don't want the air gap much. Let's call C p the speed of sound in the porous absorber. I don't know of anything that correctly models the valuable membrane effect. For most of the porous absorbers the absorption coefficient α can be estimated by the very simple relation α=0. 6 as significant) absorption at and above 60 Hz with your design. Porous model: When set to "Global", the model appears as a global parameter and is applied to all absorbers. If you download and play with the porous absorber calculator: Porous Absorber Calculator V1. Now note that the following must also be true (I'll leave aside for the moment why it must be true): K 0 /K p = C p /C 0. this incident angle is a parameter/variable that changes the effectiveness of the absorber. Predict material properties, surface impedance and absorption coefficients of acoustic absorbers. when using the porous absorber calculator, etc. 9 and its pore density. E. . June 21, 2019. Termination of such 'gaps' is clearly not mandatory. I'm using the Whealy calculator, porous absorber page. 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. 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. If you use lower GFR the Q is widened but damping is lowered. 2 0. 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. A higher fiber density leads to a more complex path inside the porous absorber therefore it implies higher interaction between sound waves and fibers. A resonant absorber is a vibrational system that “runs” on sound pressure. 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. June 21, 2019. I'm using the Whealy calculator, porous absorber page. 5th August 2017 #5. For 60 cm the situation is similar, though with different frequency and angle values. Being made from organic stuff means nothing. I'm playing around with porous absorber calculator and trying to find a good balance between effective and practical. abdo123 Master Contributor. 4 kg/m3 and corrugated board composites with densities of less than 474. The second porous absorber represents a more dense material and is labelled ‘hard porous’, with a flow resistivity σ = 30 kPa. The calculator is easy to use just make sure to select "Komatsu (2008)" for the porous model on the left side of the page. Porous Absorber Calculator Calculates the absorption curve of various porous absorber systems. 58 and trying to come up with a design. That said, we get back to this question. The composite sound absorber includes a MPP (micro-perforated panel) layer, a porous material layer, and an air cavity layer. Use the formula for the wavenumber in the porous absorber in the links I provided. These Website Terms of Use apply to the entire contents of this website under the. So attempts to calculate or predict absorption using a calculator based on a single depth are futile. (the theorical thickness is equal to the 1/4 wave length). 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. This means you can vary the angle at which the sound waves (plane waves) hit the surface of the porous absorber. Absorber ParametersHi I just wanted to share an alternative design for absorbers that i made in my listening room. drywall membranes or 4. 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. 8 1 Absorption Coefficient. Porous Absorber Calculator. According to Delany and Bazley (and others), the speed of sound in a porous absorber is given by the angular frequency divided by the real part of the complex wavenumber. Fraunhofer developed with Caruso Iso-Bond panels the VPR absorbers th. Air gap 2. For others; the diagram "B. The need for significant thickness compared to operating sound wavelength makes porous absorbers dramatically inefficient and impractical at low. They achieve a high- absorption coefficient, utilizing a relatively small volume. 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. 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. DSP like a DCX2496 is cheap and with placement and experimentation and treatment you can achieve a lot. Goes up to 170/KG/M3. Either one wants low GFR and doesn't compress, or compress as a way to emulate the higher GFR of OC 703. The nice absorber calculator you posted only confirms: 10cm is useless under 100Hz, 20cm does very little and more is physically impossible. no backing) For the air-backed absorber geometry, Strutt also allows the calculation of the transmission loss through the porous material. com. Your key says they are all rigid porous absorbers. 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. s/m2. Anyone know how I can do a simple calculation say for a 12mm gypsum board with 10cm fiberglass and a 40cm gap with solid concrete behind. This is the number we're after. 2" wide. It is assumed that there is a rigid backing (such as a solid wall) behind the. 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,. Calculate the cubic packing of uniform spheres porosity (Figure 2‑8). Step 1: Cut The Wood. Being a porous absorbent, carpet produces mid– and high–frequency absorption. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. A porous absorber may have an absorbtion curve like this. Multi-layer Absorber Calculator. For instance they assume a full boundary of fibre, like in an Impedance Tube. Show abstract. Have a look at the porous acoustic modeling/calculators. Porous Absorber Calculator Typical mineral wool is about 8-10K Pa. Share Reply Quote. The No. All. 6 0. 9th January. 2 0. 30th October 2014 #2. These porous absorber models are then used to calculate the surface impedance and absorption coefficient of different absorbents using a transfer matrix approach. and the porous material layer was established by using Delany and Bazley’s model. Share Reply Quote. 5 absorption coefficient at 250Hz. This porous absorber calculator will help you compare the effectiveness you can expect with various depths. -CSI-Spec. 8 At 2000Hz, respectively. The mass per unit area in Kg/m 2 (limp membrane). Up to four absorbers can be modelled at once, each of which can have up to four layers. Rigid Backed Porous Absorber. Multi-layer Absorber Calculator Please note that there are many factors which aren't taken into account, eg. Just don’t make the air gap deeper than the panel depth; a 1:1 ratio is best. The equation is modified to f=50/sq root(1/md). 2m porous absorber,. These calculators may not be very accurate, especially for more complex scenarios such as mixing materials. Porous absorber calculator is your friend. For example, the angle of incidence can be set as a global parameter. m for pink fluffy, 8000-1000 for Safe and Sound, 16. On one of the 4. In any case, sorry if this is a do over. Some things were way off. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. Porous Absorber Calculator V1. Helmholtz Absorber Calculator. They have specifiable one-third-octave- center band frequencies between 40 and 100Hz. Toyoda, E. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. 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). The absorption is very dependent on the type of carpet and how it is made. There is the amacoustics calculator that works for helmontz and other types of perforated and membrane panels before the absorber. A microperforated panel absorber may have an absorbtion curve like this. • Absorber 1. Porous Absorber Calculator. CryptoApplication of Porous Metals. If you are making standard porous absorbers and were trying to target say 50Hz even a 1 meter thick trap is not very efficient at that frequency IF the density is 45Kg/m3 and this material has a GFR of 14755Pa. Solving for C p gives us: C p = (C 0 *K 0) / (K p ). Can these be converted to Flow resistivity Pa*s/m2 ? (to be used in porous absorber calculator) Share Reply Quote. It is not impossible to get a theoretical efficiency of 0,5 at 30Hz with porous absorption, if you use a combination of. 45 across the frequency range. Parameter Options determine whether certain parameters appear in the Global or Absorber sections. For sure. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. A Porous Absorber Calculator is a specialized tool used in acoustics and engineering to determine the acoustic absorption characteristics of porous materials. I would look into tuned devices. 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. Here is probably a good place to promote this relatively new Porous Absorption Calculator, thanks to Demetris. . I used theIve been experimenting with the Porous Absorber Calculator V1. To get a feeling of how much was needed to absorb any given frequency, I've been using this porous absorber calculator. 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. If overthinking is a. 2 0. This app is designed to assist acousticians when designing environments such as home cinemas. There is a significant difference if one understands the concept behind porous absorption. Microperforated Panel. 4 inch absorbers have proven sound absorption values up to alpha = 0. Helmholtz Absorber Calculator. After plugging those numbers into a porous absorber calculator, I suspect the wool would perform better at greater thicknesses, e. Hello ! First post but i'm reading for years Thank to everybody who shares so much great info ! ( Thomas Northward, Boggy, GE, Jens E. . The particle velocity is at maximum at 90° and 270° (Vmax) and minimum at. Even 20cm with 20cm air gap will not result in considerable reduction around that peak. This webpage is a reimplementation of the "Porous Absorber" sheet in the. Hi! I have an example, and I'd like to know if it I possible to do the math here. g. Porous Absorber Calculator. 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. Multi-layer Absorber Calculator. Guitar in standard tuning only goes down to 82 hz, bass to 42 hz. The distance in mm between the porous absorbent. Porous Absorber Calculator V1. Even if it's peaked in planned location, most probably you'll have to measure and investigate to see results. 10 PPI) absorber plate was 13. s/m2 flow resistivity. Multi-layer absorbers composed of perforated plates, airspaces or porous materials are used widely to absorb broadband noise [1], [2]. Flow resistivity is measured with DC pressure loss. 59 Play around with with 6 kpa equal to 6000 rayls. Calculates the absorption curve of various porous absorber systems. Some things were way off. The porosity of copper foam is 0. 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. My rooms lowest mode is 39Hz, with more modes around 45, 60 Hz and upwards. First start by forming a hypothesis, something like, "The performance of broadband porous absorbers at treating room modes below 100Hz can be matched, or bettered, by narrowband helmholtz absorbers of equal or smaller size in amateur. The unit cell is a cube with sides equal to 2r where r is the radius of sphere. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. What numbers should I use for Flow Resistivity for those materials? The cavity size creates some weird dips in the response according to the graph. 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. The others perform atrociously, but even the Komatsu won't work correctly for mixing different densities. -Assume you have a 12 dB peak at 100Hz that you want to treat. 5", 89mm. 2022-03-07 11:11 am #1 2022-03-07 11:11 am #1Calculate Optimal Gap Size for Given Frequency. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. F. Its value ranges from 0 to 1, with 1 being the perfect absorber. Another important parameter of sound absorption, besides the absorbers design, is its AREA. im using this Porous Absorber Calculator to check how the GFR would help . s/m2. plastic membranes or 2. As. First of all, I came across the Porous Absorber Calculator by Chris Whealy. The distance between the holes (centre to centre) in mm (perforated panel). hi Jens, thanks for replying, from reading a few threads i see you have much more experience than I in making helmholtz absorbers. Delany and Bazley. Should I fill the corners (superchunk style) behind this back wall or simply have 300mmm of absorber with the 300mm gap as detailed above?Time-domain solvers have inherent difficulty in accommodating frequency-dependent quantities such as the specific acoustic impedance of sound absorbers, but recent developments have enabled us to consider it for some sound absorbers such as porous absorbers [1], [18], [19], [25], [27], [29]. 5" rockwool on the wall (green line, absorber 2,. There are plenty of bass traps that use membranes. It is particularly. These calculators use algorithms which do not necessarily represent reality fully. A 100mm panel with 100mm air gap gives a 0. 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. Mounting and. Rigid backing. e. If you drop down to about 4K Pa. Porous absorbers, as the name would suggest, are made from a multitude of tiny holes – cells, through which sound travels. Porous absorber calculator is your friend. 3 to 2 kg/m² (most probably between 0. Porous Absorber Calculator Preamble. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. V-corrugated absorbers have been. 2 coefficient at 50 Hz (about 0. 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. But the problem of two calculators showing different result could be related to a formula that does not include the difference between an air gap and. Served on a. 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]. In contrast, a 300mm chunk with zero. 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. GameStop Moderna Pfizer Johnson & Johnson AstraZeneca Walgreens Best Buy Novavax SpaceX Tesla. . There is the amacoustics calculator that works for helmontz and other types of perforated and membrane panels before the absorber. Multi-layer Absorber Calculator. Sound-absorbing performance of copy paper composites with bulk densities below 442. Rigid backing. 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. 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. 2 Glass wool as porous damping) towards the end is quite easy to understand. Multi-layer Absorber Calculator. The distance in mm between the perforated panel and the porous absorbent. 2 times the material thickness. Measuring the random incidence sound absorption coefficient (SAC) of porous materials is costly and requires a full-size reverberation room. Multiphysics couplings are essential to capture the effects of porous media on transport processes. 1 Review written 🎧 20 years. 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. For calculator you have: Porous Absorber Calculator Or HiFi Loudspeaker Design Your own case is a bit different as this is not strictly speaking a porous absorber but even membrane resonator benefit from absorber located within the enclosed space behind them ( explord this through the different option availlable in first link). Numerous computational models to map the acoustic effectiveness of open-porous absorbers are available for your design, for example: empirical model of. The multilayer absorber was composed of an MPP and three additional layers, consisting of polyurethane (PU) foam, jute felt, and an air gap. A. See here for a simple porous absorber calculator. This relationship can be evaluated analytically only for few simple material geometries. The available calculators allow you to see the impact of this absorber on the absorbers frequency response for different depths and spacings. Username: Password: Forgotten password? Register home | terms of use | privacy policy | links | contact: Copyright. Draw couple of points (tape crossed) on this line with about 5cm distance (2") between points. Someone smarter than me can probably elaborate further. 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. 3. 15 at 40 Hz), which I'm guessing isn't amazing. s/m2 for Roxul SNS and 24,000 Pa. These briefly and simply cover the basics (and have lots of pictures ). Multi-layer Absorber Calculator. Thermohanf porous absorbers. Actually it doesn't. If you drop down to about 4K Pa. , JH Brant, DanDan, Avare, can't name you all. This may be an old thread, but the problems with the slotted panel graph still persist in the latest version 1. Obviously I'd need more surface area to make a real dent in a room that size. doc Porous Absorber Calculator V1. For thicker absorbers and irregular slat sequences measurements are needed. Mechel and Ggrundmann. According to the porous absorber calculator, the depth you should use fluffy over mineral wool is somewhere around 7-14 inches, depending on GFR estimates and the frequencies you're targeting. 8 & you will see the LF absorption. Width of hangers is used to define lowest frequency, membrane absorbers isn't included in this simple model/formula, and 1. 1 for IsoCal! Your handheld building acoustics calculator 👋. It calculates the acoustic absorption curve of a variety of absorption devices mounted against a rigid backing such as a brick wall. Behind the template is glass fibre filling with density 6-8 lbs/ft³ (96-128. Rigid Backed Porous Absorber. The setup follows international standards with about 10 m² of slat absorber in an echo chamber. 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. s/m2, at which density going beyond 12" of thickness offers minimal benefit, and getting more than 50% absorption at 50Hz doesn't work. 16000, 23400, 27000 (c/o NASA!). The calculators can save you from having to tear stuff out that is worse than it was: Porous Absorber Calculator V1. 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. . 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]. 58 of Porous Absorber Calculator. Numerous computational models to map the acoustic effectiveness of open-porous absorbers are available for your design, for example: empirical model of DELANY and. 5th March 2014 | Show parent #17. It calculates the acoustic. I need to make a keyboard macro with that sentence. 6 0. 's most successful trap, after many many attempts, was a panel one. Here's the link: Porous Absorber Calculator. Delany and Bazley. The absorber geometry is still cylindrical, but instead of being subdivided into two segments the cylindrical volume is subdivided into N sectors. Dennis Foley says: May 4, 2023 at 5:10 pm. . 58 (RPG´s BAD template is 600x600 mm with 512 holes, each Ø12,7 mm. Wilson, simplified relaxation model. AFAICS, the. Calculates the absorption curve of various porous absorber systems. To get a feeling of how much was needed to absorb any given frequency, I've been using this porous absorber calculator. Hey Guys, I wanted to try a few calculations of membrane absorbers to see how the different air and absorber depths affected the absorbers. 35 per sq metre here are some specs for the products. The resonant frequency could be calculated using e. The TMM was employed to calculate the specific acoustic impedance of each layer in the multilayer porous absorber, and the results were used for theoretical sound absorption prediction. 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. . 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 blue and red are OC703).