Absorption software sound

It can also assess impact sound and rain noise of floors and roof. SysTune is an audio measurement software capable of measuring and processing full-length impulse responses in real time. Next to the sole quality of the measurements performed SysTune offers a large set of unique features to make a technician's life easy and speed up the work. All values are approximate. Figure 3: Absorption values. Note that the softer the material, the more absorption.

The more dense and hard the material, the less absorption. There are several things that affect absorption. Some factors include: material composition, humidity, material thickness, and material position. Porous materials typically absorb sound better than very dense materials. Examples of porous materials include cloth, foam, fiber glass, and acoustic tiles. Porous materials present a larger amount of surface area to the advancing sound waves. The fibers or particles of the porous material are able to vibrate and dissipate the sound as heat.

Very dense materials concrete, cinder block, glass tend to reflect most of the incident sound. The speed of sound is affected by the humidity in the air. The speed of sound increases as humidity increases. As the speed of sound increases, the absorption also increases, as shown in Figure 4. Figure 4: Effect of humidity. When performing an absorption test, samples should be stored for several days in a humidity controlled room to ensure they are at the desired humidity for the test.

With all else being equal, increasing material thickness increases the absorption performance at lower frequencies Figure 5. It has been experimentally determined that peak absorption of a frequency occurs when the material thickness is about one-quarter the wavelength of the wave. Figure 5: Absorption performance versus material thickness. Low frequency sounds have longer wavelengths, therefore the material has to be thicker to absorb lower frequency sounds.

Sound absorption depends on angle of incidence of the incoming plane wave. Figure 6: The angle of incidence of the incoming plane wave. In addition to the angle of incidence, material position relative to the supporting wall matters. For example, mounting the absorptive material flush with the wall versus mounting the absorptive material and leaving an air-gap between the material and the wall will affect the absorption coefficient. Figure 7: The effect of air between absorptive sample and reflective wall.

Experimental data shows that leaving one quarter of a wavelength between the wall and the absorptive sample maximizes absorption at a given frequency. This is because of the relationship between the pressure and the air molecule velocity in the standing wave that the tube creates.

Figure 8: In a standing wave in a tube, air molecules colored in gray form alternating areas of low and high pressure orange line. Some molecules of air stay in fixed positions at nodal areas along the tube colored in blue while other molecules colored in red move rapidly between the alternating areas.

Sound is absorbed when there is friction between the air molecules and the absorptive material causing the sound energy to dissipate as heat. Looking at the graphic, you can see that air molecules move the most at one quarter wavelength away from the wall.

Therefore, the absorptive material should be placed one quarter wavelength away from the wall to maximize the absorption of the wave. Figure 9: Absorptive material pink is placed one quarter wavelength away from the wall to maximize absorption.

Note that placing the material one quarter wavelength away from the wall maximizes absorption for that corresponding frequency. Figure The blue arrows represent sound waves. Direct incidence: all sound waves approach sample at same angle. Random incidence: sound waves approach the sample at random angles. One end of the tube is connected to a sound source which outputs a broadband range of sound waves.

The other end of the tube holds the sample to be tested. Therefore, the sound waves approaching the sample are both direct incidence and normal to the sample. The tube ends in a rigid termination. A pair of microphones are positioned just before the sample.

See Figure 11 below. Figure Top: Impedance tube. Bottom: cross section of the impedance tube to show sample location within the tube. Samples of the test specimen must be cut to fit within the tube. Care must be taken when cutting the samples as the boundary conditions between the sample and the tube can greatly affect the resulting measurements. The model is accurate for high porosity materials i. The program has the unique ability to predict random incidence absorption taking into account the variation of absorption with angle of incidence and the diffraction by the edges of the material.

Within limits this will give a good estimate of the absorption that would be measured in a reverberation chamber. The performance of slot absorbers, perforated facings and panel absorbers may be predicted by entering the physical dimensions of the slots or holes. Slat absorbers on one- or two- layered porous absorbers. Variable dimensions of slats and ribs. Slot absorbers on one- or two- layered porous absorbers. Variable dimensions of slots and ribs Perforated facings on one- or two- layered porous absorbers.

Variable dimensions of perforation Panel absorbers on one- or two- layered porous absorbers.