PaulRain. . This relationship can be evaluated analytically only for few simple material geometries. The composite sound absorber includes a MPP (micro-perforated panel) layer, a porous material layer, and an air cavity layer. Acoustic plate absorbers have NRC ratings of 0. 5 rayl/m. See here for a simple porous absorber calculator. 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 others perform atrociously, but even the Komatsu won't work correctly for mixing different densities. This app is designed to assist acousticians when designing environments such as home cinemas. Users with access to the relevant academic papers. I was thinking of using slats 3cm / 1. DanDan, Regarding your remarks on ratio of absorbent to air gap for the 6" depth I have available to me (2" absorb+4" air vs. See here for a simple porous absorber calculator. 6m walls, there is a 2. ↑ top; home; New Product Alert; classifieds; reviews; deal zoneThe rectangular version is easier to build and saves material. 1. 4 0. 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. When sound propagates in small spaces, such as the interconnected pores of a porous absorber, it loses energy. 4 0. 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. 2. s/m2 flow resistivity. 1. This membrane effect is "tuned" to a specific frequency depending on the density and thickness of the material. Porous Absorber Calculator V1. 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. Whealy C. Perforated panel absorbers have holes in their face and diaphragmatic absorbers have a solid face. 5rayls/m) 1200mm Porous Absorbent, 1500 Pa. There is also a loss in momentum due to. 2m porous absorber,. A cylindrical geometry is used so that the multi-sector SeMSA. 1 (a) that comprises a cavity, neck, lids and porous material. But Basotect has a coefficient of 0,8 at about 800Hz while Sonorock reaches the same value at about 1,2kHz. Flow resistivity. Porous Absorber Calculator 4" mineral wool is actually 3. So attempts to calculate or predict absorption using a calculator based on a single depth are futile. Thank you Can you help me clarify the difference between "random incidence" and "normal incidence" options in the porous absorber calculator? Share Reply Quote. I think I have read that ideally one shouldn't mix materials in broadband absorbers. 20 per sq metre the Fibertex 350 is 60kg/m^3, comes in 1500*900*50mm sheets and is $20. 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. s. "ω" is angular frequency, which is defined as 2*pi*f. Play a little bit with different thickness and different Flow Resistivity you will see your self. (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. This only works with absorbers of uniform thickness and triangular bass traps obviously have varying thickness. e. this formula or e. 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. 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. 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. I am quite a noob but i’ve been researching a lot about it the past few weeks. The optimal range of key design features of the double-layer porous wave absorber as follows; submergence depth (d 1 / h) of the upmost plate is 0. 5 @ 500Hz, and 0. So for porous absorber lower is good. Guest. 1. 70% of original porous metal absorber and that 31. The angle of incidence can be adjusted. It depends only on the pore geometry . The spring is the air inside the cavity of the resonant absorber. s/m 2 Porous Absorber Calculator. e. with a lot of air behind them, like about 1,2m. Hi! I have an example, and I'd like to know if it I possible to do the math here. s/m 2 (porous absorbent). This will be against a wall, not in a corner. 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. Even if it's peaked in planned location, most probably you'll have to measure and investigate to see results. ) broadband absorbers. Is the “Rigid Backed Porous Absorber” calculator not “correct” (within reasonable limits of course)?. A porous absorber may have an absorbtion curve like this. 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. Porous Absorber Calculator. The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. The pancake absorbers are different from conventional porous materials in two respects. drywall membranes or 4. Otherwise your just making another reflection point. 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). . The sound dissipation mechanism in MPPs is based on the principle of the Helmholtz resonator (HR) []. 0 with a German user interface and is developed by Marshall Day Acoustics. Multi-layer Absorber Calculator. The Porous APorous Absorber Calculator Sent from my iPhone using Tapatalk. 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. Rigid backing. Porous Absorber Calculator. 2 0. The transfer matrix method (TMM) was used to calculate the surface impedance of each acoustic unit-cell of the composite multi-cell sound absorber, and the SAC of the composite multi-cellsound absorber was predicted by using theequivalent circuit method. This paper shows that the predictions from impedance tube measurement and the empirical method have reasonable accuracy for the determination of the random incidence SAC above 400 Hz. The thickness of the sound absorber was changed from d: [1. 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. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. e. 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. For flow resistivity, look at the datasheet for your specific type of mineral wool. It is not impossible to get a theoretical efficiency of 0,5 at 30Hz with porous absorption, if you use a combination of. Dotted lines indicate that the model used to estimate absorber properties has been used outside of its applicable range. Goes up to 170/KG/M3. The formula is: \alpha_m = A / S αm = A/S. 1 Website for Pro Audio ; The No. The thickness of the porous absorbent in mm. The prediction of the sound absorption coefficient in diffuse field conditions is of great interest to an acoustic project. The actual average sound absorption coefficient of the microperforated panel + cavity + porous metal + cavity sound absorber in the 100–1800 Hz range reached 62. Joined 2012. 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. g. 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. 8 1 Absorption Coefficient • bass trap1 • bass trap2 • side panel • back panelMembrane absorbers work best with lower-frequency and bass frequencies. 35 absorbtion at 30Hz and increase to 0. Single absorbers: objects such as tables, chairs, people, etc. I'm only taking axial modes into account. 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. Termination of such 'gaps' is clearly not mandatory. 067, equal distance between plates (s / h) 0. I've recently written a porous absorber calculater for my own use and have decided to make it available over the internet. The thickness of the porous absorbent in mm. Calculates the absorption curve of various porous absorber systems. The mass is the cabinet and front wall or diaphragm. 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. 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. Here is probably a good place to promote this relatively new Porous Absorption Calculator, thanks to Demetris. In any case, sorry if this is a do over. New Porous Absorber Calculator. • Absorber 1. and a Calculator Porous Absorber Calculator Coincidentally, I found those links another way earlier today and spent some time with them. 59 Here is another: Porous Absorber Calculator The trick seems to be finding the Flow Resistivity for the material you want to use: Pa. Wherein, there is a cylindrical porous absorber which is sealed behind a quartz window. Air gap 1. 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. To enhance the performance of porous absorbers, incorporating an airgap behind them proves to be quite effective. Air is a viscous fluid, and consequently, the friction with the pore walls dissipates the sound energy. which could be applied to porous absorption with and without perforated facings3. Toyoda, E. 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. sEither way, the combination or resonant and porous absorbers work very well, as the porous absorbers will cover the wet portion of your room’s acoustics while resonant absorbers will clean up the stubborn bass mess where porous absorbers may fail. Maybe with tuned absorbers or perforated panels, but there are others here that have more experience with that. Just don’t make the air gap deeper than the panel depth; a 1:1 ratio is best. Helmholtz Absorber Calculator. 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. Flow resistivity. These porous absorber models are then used to calculate the surface impedance and absorption coefficient of different absorbents using a transfer matrix approach. 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. The nice absorber calculator you posted only confirms: 10cm is useless under 100Hz, 20cm does very little and more is physically impossible. 59 There are also some interesting studies from the BBC and NASA which support this approach. 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. You will fast get a feeling which absorber thicknes is the next one to build. s/m2, at which density going beyond 12" of thickness offers minimal benefit, and getting more than 50% absorption at 50Hz doesn't work. g. 2 0. 5αCL/A (C is the circumference, L the length, and A the. If you only record singing, there is no need to worry about sub 100 hz frequencies. As vibrational science will tell us a resonant absorber is a mass vibrating against a spring. DSP like a DCX2496 is cheap and with placement and experimentation and treatment you can achieve a lot. if the calculator is a inaccurate source may this be please mentioned. Username: Password: Forgotten password? Register: 20 50 100 200 500 1000 2000 5000 10000 20000 Frequency (Hz) 0 0. Obviously I'd need more surface area to make a real dent in a room that size. The distance in mm between the porous absorbent. Porous materials, particularly polymeric foams, are the most effective sound absorbers among a wide range of existing sound-absorbing materials. 69%, which. Select frequency range : 20 - 300 Hz. 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. It doesn't perform as a whole system with a cavity (which isn't sealed), it's rather a velocity based absorber which. 69%, which was superior to that 25. . 1. Username: Password: Forgotten password? Register: Calculator. 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. 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. s/m2, at which density going beyond 12" of thickness offers minimal benefit, and getting more than 50% absorption at 50Hz doesn't work. this formula or e. Multi-layer Absorber Calculator. Parameter Options determine whether certain parameters appear in the Global or Absorber sections. 2017, 116, 311–316. This graph shows the difference between RS45 and RS100 Multi-layer Absorber. Absorber Parameters. This app is designed to assist acousticians when designing environments such as home cinemas. Since membrane absorbers require high level of precision to perform at the desired frequency, they are often customized for a specific application. For a sufficiently thick porous absorber (eg. There are generally two types of bass traps: resonant absorbers and porous absorbers. s values: Pink R-30 insulation - 4000 pa. 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). Absorber ParametersHi I just wanted to share an alternative design for absorbers that i made in my listening room. 90 cm) through a calculator, the benefit from more depth seems to be rather minimal. 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 sandwich acoustic structure consists of an air cavity layer in between two MPP layers, which. 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. But in my design, the open area will also be roughly 50%, so I figured the results would be useful anyway. Using a perfboard does not mean you no longer need fabric,. i think that most isolation material or foam benefit from stacking in depth and make bass trap from it. If you know any other quality tools, please tell me! List of other quality acoustic calculators besides amcoustics. Porous Absorber Calculator - Results According to the calculator, you will still get significant (I consider anything over . 6 0. s/m2, a 2ft thick absorber can be 70% effective at 50Hz. -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. Being made from organic stuff means nothing. This was measured and also predicted in Ethan's room mode calulator for thePorous absorbers need considerable thickness to maximize the absorption performance at low frequencies since the minimum thickness required is usually one order of magnitude smaller than the. I'm using the Whealy calculator, porous absorber page. 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. Porous Absorber Calculator. s/m 2. s/m2 for Roxul SNS and 24,000 Pa. 2 coefficient at 50 Hz (about 0. 1. If its. The angle of incidence can be adjusted. Share Reply Quote. Hole spacing. You can play with the porous absorber calculator to find suitable dimensions. 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. 5m, you'd have to cover virtually all surfaces to reach effective absorption - your expectations are wrong It also looks like you used the multilayer porous absorber calculator (with one of the layers being a perforated panel) and not the. 6 0. The porous absorber calculator does not offer a complete solution for diagonal traps. (the theorical thickness is equal to the 1/4 wave length). Average sound absorption coefficient formula. 080, and its porosity (P 1) 0. 100mm Porous Absorbent, 10000 Pa. It is particularly valuable in designing soundproofing and acoustic treatment solutions for various environments. For fibreglass enter 16816. The porous absorber calculator says 'yes' when I plug in a GFR of 2500. In contrast, a 300mm chunk with zero. It is assumed that there is a rigid backing (such as a solid wall) behind the. Hope you find it useful. absorption offered by the 3887rayls/m. Step 1: Cut The Wood. 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. 5th August 2017 #5. 1. The impact of using the partially porous media in the absorber on the efficiency of PTC (parabolic trough collector) has been investigated. 2 0. Porous Absorber Calculator. Another important parameter of sound absorption, besides the absorbers design, is its AREA. Guitar in standard tuning only goes down to 82 hz, bass to 42 hz. All. Porous Absorber Calculator. If you change the vibrating mass and stiffness of the. 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. If the stuff you have is flexible building insulation, 8000-10000 Pa. 2 Glass wool as porous damping) towards the end is quite easy to understand. The porosity of copper foam is 0. Porous Absorber Calculator Last edited: Oct 18, 2021. Oh well, experimentally bruteforcing it. Comparision: Porous Absorber Calculator - Results In this math example, Sonorock actually goes lower in terms of absorption than Basotect. Tortuosity was essential a capacitance test with a wetted material. 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. Normal incidence. 6 as significant) absorption at and above 60 Hz with your design. Show abstract. All the source code for this app is availble on my Github repo "porous_absorber". 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. S. In this analysis, porous absorbers with 20,000 Ns/m 4 flow resistivity was used. The measurement results serve the evaluation of the required complexity of the absorber models to be applied to model your specific materials. 2m wide, 1. Porous Absorber Calculator. 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. If perforated panel with porous absorber trap isnt the way for me to go, then what other options should I consider? Share Reply Quote. 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. . s. For sure. Standard pink fluffy is ~5,000. . The equation is modified to f=50/sq root(1/md). Diaphragmatic absorbers are good for going after frequencies below 90 Hz. Hey Avare, would love to ask you a couple questions to gain deeper insight- Quote: Originally Posted by avare ️ Corner absorbers are good at mid and high frequency absorptio. perforated wood over acoustic foam porous absorbers. 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. A reset button is provided which returns all global parameters (and parameter options) to their default values. For membrane absorbers, a first approximation is k/sqrt(d*M), where k is between 50 and 60, M is the mass-per-unit-area of the membrane (kg/m^2) and d is the sealed cavity. 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. I constructed a ~100 mm thick absorber using rockwool (mineral fibers) and modeling shows it is effective down to low hundreds. Broadband absorber and gas flow resistivity. With 40cm thickness, the 040 would actually be better without airgap according to the Porous Absorber Calculator. 16,600 is OC703, 5000 is fluffy. Slotted Panel. Flow resistivity: The flow resistivity of the layer in Pa. After plugging those numbers into a porous absorber calculator, I suspect the wool would perform better at greater thicknesses, e. placed in the middle of the room. Some carefully placed spacers (smaller strips of insulation) could keep it off the wall. Much ore than that (~200mm+) makes them even better at lower freq. C0 is the speed of sound in air, which we'll say is 343 m/s. 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. My Studio. . Play around with the flow resistivity on a porous absorber calculator. not easy but it's doable. Ye Old Porous Absorber Calculator. Porous absorbers. For instance they assume a full boundary of fibre, like in an Impedance Tube. 4 kg/m3 and corrugated board composites with densities of less than 474. If I want to calculate an optimal GFR for a given depth of porous absorber, how would I do that with a formula? Share Reply Quote. Absorption Area. 50%) 400mm Porous Absorbent, 4000 Pa. Running your suggested depths (70cm vs. I changed the concept from slat to perforated absorber. Here's the link: Porous Absorber. Username: Password: Forgotten password? Register: 100 200 500 1000 2000 Frequency (Hz) 0 0. Porous Absorber Calculator. This calculator estimates the absorption coefficients of multi layer porous aborbers. Microperforated Panel. The normal incidence sound absorption coefficient of porous materials can be predicted when the specific acoustic impedance of the material is known. Tuned pressure absorbers work only if pressure at tuning frequency is present, they will not work i. 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. 1) why do my. 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. (broadband) the glasswool Quietel is 130kg/m^3, comes in 2400*1200*25mm sheets and costs $33. Wilson, simplified relaxation model. Its value ranges from 0 to 1, with 1 being the perfect absorber. Calculation models and input parameters. First Reflection Calculators Wavelength - Frequency Calculator Calculate Room Modes Calculate optimal Room Dimension Reverb (RT60) Calculator The Wall Behind The Loudspeaker Absorbers Helmholtz. 1 (b) is porous. I don't know of anything that correctly models the valuable membrane effect. From the first formula we can calculate specific airflow resistance simply by multiplying airflow resistivity [Pas/m2] with thickness of the porous material [m]. 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. 35 per sq metre here are some specs for the products. s/m2 for Absorber 1, then. online calculators for porous absorbers. This webpage is a reimplementation of the "Porous Absorber" sheet in the above spreadsheet using Rust and Web Assembly. The setup follows international standards with about 10 m² of slat absorber in an echo chamber. Liu, G. The available calculators allow you to see the impact of this absorber on the absorbers frequency response for different depths and spacings. 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. A thought occured regarding the tuning of these panels. 1 Website for Pro Audio. 8 1 Absorption Coefficient. Model: Allard & Champoux (1992) Absorber Parameters. Porous Absorber Calculator. It doesn't perform as a whole system with a cavity (which isn't sealed), it's rather a velocity based absorber which. If overthinking is a. As a result, a combination of porous and membrane technologies should be able to absorb the vast majority of frequencies. I don't understand why the porous absorber calculator wouldn't scale to small room acoustics (as some have said); even if its results are based. Maybe with tuned absorbers or perforated panels, but there are others here that have more experience with that. The curve changes a bit as I vary the air flow resistivity (I'm using roughly 5000kRayls/sq. 4 0. The calculator in question does not take into account the mass of the porous material (that has some effect on low frequency performance due to the membrane action it might cause), only flow resistivity, and although the most important factor; the mass can sometimes affect the result quite a lot, even if the FR value is the same. 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. These porous absorber models are then used to calculate the surface impedance and absorption coefficient of different absorbents using a transfer. If you can find the Gas Flow Resistivity of the product you could predict the absorption spectrum using this calculator. 8 kg/m3 can be alternatives. 8 kg/m3 can be alternatives. - the area covered with the absorbers is not large enough (you mention 36Hz, which is a wave of 9. 6 0. effect_of_perforated_sheet_open_area. Absorber thickness. V-corrugated absorbers have been. According to the Porous Absorber Calculator this should give good absorption down to at least 50hz (and probably lower). hi all i have 2 rooms that need Treatment at Specific frequency range And I think of making traps with perforated wood my q is how reliable is the Porous Absorber Calculator V1. Most bass will be absorbed by the rear wall absorber anyway; I just want something that better than nothing in the front. Look at the densities. Figure 2-8: Typical ordered porous medium structures. e. 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. Member. 2m depth in my calculations is only for hangers. Porous Absorber Calculator Preamble. You may be overthinking it. For others; the diagram "B. 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].