J, Yes, and companies do a good job of that. Everyday someone calls me and wonders why the foam they put up in their studio doesn't stop the garbage truck noise.

J, Thank you. One of the great myths perpetuated by acoustic product manufacturers is that building insulation is the cure all for all absorption needs for music and voice. In fact, most of their products contain this material and are just repackaged building insulation with a different name. Music and voice is different and must be treated with respect in rates and levels of absorption. You must place certain rates and levels of absorption below 500 Hz. that building insulation can not offer or achieve. Another issue is the toxic quality of these materials. The building materials are composed of steel and plastic based fibers that are lighter than air and are inhaled by the workers who install them. We do not allow these materials on any of our build sites for performance and health reasons.

Hi Tino, You are correct. Material thickness and density are the two most important variables when it comes to energy absorption down to 100 Hz. All frequencies below 100 cycles require special sound absorbing technologies to achieve results that will absorb enough energy to make an audible difference. When I say audible, that term comes with many meanings in today's literature. You must look at a product's ability to directly impact low frequency energy attack and decay rates. Anything else is just a band aid on an acoustical artery cut. Thanks Dennis

+Luoyisi Shimisi Vocal rooms have special rates and levels of absorption that must be dealt with when dealing with frequencies above 100 Hz. Fill out the information in this link and I can better assist you. www.acousticfields.com/free-acoustic-treatment-room-analysis-tell-us-room/

I found that a vocal booth's primary function is isolate from other noise and to cut down on the high frequency slap-back echos, say 5 kHz and up. You can get pretty far with just carpet floor and thin lightweight foam. The walls should be solid enough so the vocal mic doesn't pick up too much of what's going on in the other rooms. You're running an 80 or 100 Hz low cut on vocal channels anyway (very few voices go that low and when they do, there's not a lot of sound pressure there) so you kinda want it to reverberate in the vocal booth a little bit, you just want the high mids and treble to sound dry so you can slap whatever reverb on there.

+tecnolover2642 Absorption coefficients are based upon the capacity of one square foot to absorb what percentage of that frequency. They are useful calculations in determining the amount, type, and position of that specific material. You use them to determine the rate and level of absorption that goes well with the room's intended usage.

J, Thank you for your following. If you have any ideas for topics, just let us know.

The process you are referring to and using in your example is exactly as you state. Adding additional limp mass layers is not highest and best use of the precious real estate space we all have in our music rooms. If you follow the quarter wavelength rule, you can see how much depth just a 40 Hz. wavelength needs. At 39 long, you must have at least 9' +. This is one of the major reasons behind our diaphragmatic absorbers. With diaphragmatic absorption, you can go lower and absorb even more than any limp mass pile in a box. That said, our diaphragmatic absorbers weigh 200 lbs each! You can see the performance results tested by Riverbank Acoustical Labs on this page www.acousticfields.com/product/acda-12-activated-carbon-diaphragmatic-absorber/ 100% absorption at 50 Hz. and 63% at 40 Hz. In short, its a beast. Thanks Dennis

Acoustic Fields That certianly sounds impressive. I'm not that familiar with diaphramatic absorption although I understand them in principle. Thanks for the response.

Hi KennyTew2, my pleasure. This blog post and video help explain the diaphragmatic absorption process better www.acousticfields.com/bass-absorption-why-the-power-of-diaphragmatic-absorption-is-your-only-hope/ Any questions, don't hesitate to call or mail me as always happy to help. Thanks Dennis

Acoustic Fields Much appreciated.

Panel depth produces the panel's resonant frequency. A resonant frequency is how low the unit will absorb down to. Frequencies above the resonant frequency will be absorbed. Those frequencies below the resonant frequency will not be. Panel depth says nothing about how much energy will be absorbed above that resonant frequency per square foot of panel surface area. The internal cabinet fill material determines the rate of absorption above the resonant frequency. You must match the rate and level of absorption to music and voice not noise. Music and voice are different than noise.

@@AcousticFields yes but my question is and i will try to explain my self , won't the rockwool panels work to some extent in low volumes ? meaning , sound is a physical waveform with many frequencies and amplitudes right? so there must a be a treshold where all the sound is absorbed and wont excite room modes using this cheaper tech.... i was reading and aparently energy is equal do amplitude and frequcny square so...E = A2...does this mean all waveforms with energy below 1000joules or something is ok=???

@@ayamaprantenna but its a mechanical waveform so i think that it depends on the volume it creates as, when the energy hits the wool it all gets transformed without resonating i think....at low volumes think rockwoll will be effective down to 20hz man

@@ayamaprantenna its more like energy conversion from mechanical to thermal

@@ayamaprantenna so your saying the laws of thermodynamics are wrong???? Yes it is absorbed compeltly doesn't change any pitch

Hi J, Published absorbent coefficients are based upon the sample size and cover a 1 sq. ft. test area if the testing is adhering to established and accepted criteria. You must then take that 1 sq. ft. area per sample size and then calculate how much square footage of that chosen material you need to impact a frequency and amplitude change for your given issue. Total amount of material required is based upon amplitude of frequency issue.The mistake people make when looking at the data is that they assume since the product they are looking at absorbs 100% at a given frequency that placing a single product will accomplish their absorption requirements. You must match the products ability to absorb at a particular frequency with the amplitude of the problem and them calcualte corresponding coverage requirements.

I don’t know ASTM standard since here in Europe we use ISO but I’ve seen many ASTM compliant tests with alpha values over 1,3. My opinion is bass absorption should be measured in Kundt tubes because reverberant chambers and standards are not thought for frecuencies below 100 Hz and the results can be manipulated to get what you want.

You are correct. You do not need absorption levels to be at 100 %. However, it is critical to understand the science behind claims, especially in the low frequency absorption area, that are made by acoustic product manufacturers. What we do need is a better understanding of what constitutes real absorption rates and levels from existing technologies that are represented as low frequency sound absorbing devices. It appears to us that most companies apply the term low frequency absorber to their products when the laws of physics tell us that this just can not be. There appears to us to be a big difference between the label placed upon the product and its actual performance capabilities as defined by the laws of physics.

Absolutely. And where the absorber is expensive youcan extend the range downwards usefully by standing it away from the wall a little. If the room is already fairly dead ayhigher frequencies the front face should be supplemented with a sheet of something like vinyl to make it a little refective to high frequencies.

donepearce It is important to realize how lower frequency sound absorbing devices work in order to maximize their effectiveness. Once you know how they all work best, you can find those triggers within the room. Pressure activated, absorption technologies, need to locate in areas of highest room boundary pressure. This high pressure region can be measured at distances of 1/4 " from wall surface. We have measured over 100 rooms in this manner. As one extends out towards room center, pressure levels become less and the diaphragmatic and membrane type of low frequency absorbers will not work at maximum efficiency. Their whole performance existence depends on pressure. Pressure is the key that starts the engine; no key, no start, no absorption. Placing a sound absorbing technology that works on air flow and molecular speed to generate heat through friction for absorption process to occur are more effective away from room boundary surfaces because any physical positioning that increases the air flow across the most surface area of the unit is beneficial to the overall unit's performance. These units will not be able to obtain the same rates and levels of low frequency absorption as pressure activated units. Thanks Dennis

He was just using 100% as an example of what it what it would take to absorb 185hz. Now, do you need to absorb 100% of anything? Let's say you put 6 feet or whatever he has around the entire room where it's on every wall, ceiling, and floor, then there would be no 185hz bleeding outside the room into the outside, nothing at 185hz would enter the room from the outside, and 185hz would not get reflected back into the room, so you'd only hear 185hz from the sound source and not from anywhere else. if it had only 80% absorption and your entire room was covered with that product, then you'll get a little bleed through and maybe some will get reflected back into the room. I think that's what he means. Obviously, you aren't removing 185hz from the sound source. you'd need something else to do that, that's an electronic filter of some sort that completely removes specific frequencies emitting from the speaker.

If you are talking about room treatment, you are talking about managing what's emitting from the sound source and what gets absorbed or reflected or diffused within the room. Barrier technology is what is used to prevent bleed through between the room and the outside area.

Roberto Cosenza I'm trying to make the complicated as simple as possible. Its the science that some people have twisted over the years to confuse people into buying their products. I'm trying to go the other way and help people do their own thinking. But if you want the official science lab reports on our products performance you can find that on our website at www.acousticfields.com. I just prefer not to bash people over the head with that stuff.