Technetics Group FELTMETAL™ Acoustic Media
Technetics Group FELTMETAL™ Acoustic Media is an engineered, porous material made of sintered metal fibers. The size of the fiber, porosity and thickness of the fibers combine to control the desired flow and sound absorption. To enhance the structural properties, the metal fibers may be reinforced by sintering to screen mesh or perforated plate.
FELTMETAL™ Acoustic Media is produced from fibers having diameters ranging from 50 to 150 microns. Finer fibers offer the advantage of lighter weight and lower non-linearity factors.
- Stainless steels for service temperatures up to 930°F [500°C]
- HASTELLOY®-X for service temperatures up to 1100°F [600°C]
- FeCrAlY for service temperatures up to 2000°F [1100°C]
Advantages of Technetics Group FELTMETAL™ Acoustic Media
- High temperature resistance
- Optimum performance through acoustical impedance matching
- Readily cleanable
- Excellent erosion resistance
- Low non-linearity factors
- Exceptional performance at high frequencies
- Corrosion resistance
- Reliable performance in wet conditions
How FELTMETAL™ Acoustic Media Attenuates Sounds
When a sound wave is reflected from a hard surface of a silencer, constructive and destructive interference may occur, resulting in a series of maxima and minima in wave amplitude. If a porous material is placed across the wave pattern, the movement of air molecules through the material is converted to heat, resulting in a reduction in sound intensity. This reduction is highest if the material is placed at a location where the air molecule velocity is a maximum ¼ of the wavelength. The flow resistance of the porous material is critical to the efficiency of the attenuation process. If the resistance is too high, then the material acts as a hard surface and reflects the sound. If the resistance is too low, then the sound wave travels freely through the material. In either case, the sound attenuation is less than optimal. Flow resistance is defined as the ration of pressure drop across the material to the velocity of gas through the material. This ratio is expressed in cgs rayls. For air at standard temperature and pressure, the maximum attenuation occurs at 41.1 rayls.