Noise-induced hearing loss is an extremely prevalent health concern for individuals who work in the manufacturing industry. In fact, over 40 million people in the United States currently experience some form of hearing loss. Among these individuals, nearly 10 million Americans suffer from hearing problems caused by noise. This condition is often caused by repeat exposure to loud noises, particularly those that exceed 85 decibels, which is common in manufacturing facilities. To stave off the harmful effects noisy machinery and loud manufacturing floors have on employees, many manufacturing facilities are turning to industrial silencers to reduce this risk and aid in acoustical attenuation. To better understand the different types of industrial silencers, and the way they work to reduce dangerous noise levels, we must first understand the basics of acoustic attenuation.

Understanding Acoustic Attenuation

Acoustic attenuation is the weakening of sound as it travels and passes through different materials. Sound waves are distributed, and thereby diminished, in two main ways. The first way this happens is through absorption. Acoustic absorption uses porous materials to absorb sound waves and transform sound energy into heat energy that is then dispersed throughout the atmosphere. The second element of acoustic attenuation is scattering. Scattering redirects sound waves away from their original path and sometimes reflects the waves back toward the original noise source. Acoustic attenuation combines these two methods to effectively reduce noise volume and perception. The industrial silencer types listed below use a combination of scattering and absorption to attenuate sound in an industrial setting.  

Industrial Silencers and Applications

Reactive Silencers

Similar to the silencers used for automobile exhaust systems, reactive silencers are also commonly known as mufflers. Like car mufflers, industrial reactive silencers are designed with multiple chambers and perforated tubes. These perforations redirect the sound waves and reflect them back toward the source of the sound and effectively reduce the volume of the noise we hear. These silencers do not contain any acoustic insulation and attenuate sound primarily by scattering and reflecting the sound waves. One main benefit of reactive silencers is that they are relatively easy to clean because they do not contain fibrous materials, and they create negligible pressure loss. These silencers are also typically quite small, which makes them suitable for engines and exhaust systems. Reactive silencers are commonly used for fixed speed machinery, such as generators and blowers. They are best used for machinery that produce pure tones and noises that range from low to medium frequency.

Absorptive Silencers

Unlike reactive silencers, absorptive silencers primarily attenuate sound by absorbing sound energy, rather than reflecting it. These silencers use fibrous and porous packing materials to absorb sound waves and dampen the sound volume. As the sound waves travel through the insulative materials, the sound energy is partially transformed to heat energy, which is then dispersed through the air. The thickness of the acoustical lining used in absorptive silencers varies and designed to meet specific project requirements. The thickness of the lining is often dependent on the predominant frequency of the noise. Absorptive silencers are particularly effective for high noise frequencies between a range of 500 to 8,000 Hz. They can also be used for frequencies outside this range, though adjustments to the thickness of the absorptive lining is required to provide the desired level of attenuation.

Since absorptive silencers rely on acoustic absorption rather than reflection of sound waves, they require minimal airflow to properly attenuate sound. For this reason, absorptive silencers are commonly used in centrifugal compressors, industrial fans, and gas turbine inlets. Additionally, they can be used in gas turbine exhaust systems and fans. Absorptive silencers can be installed vertically or horizontally, which makes them very popular in power and process applications. Absorptive silencers are also commonly referred to as parallel silencer baffles or splitters and can be specifically designed to optimize pressure drop and meet all noise criteria for your project.

Steam Vent Silencers

Also known as gas silencers, steam vent silencers are designed to reduce the amount of noise created by gas or steam. Steam vent silencers work differently from absorptive and reactive silencers, as they do not attempt to reflect sound waves and may or may not use absorptive materials. Instead, vent silencers attenuate noise by diffusing the flow of pressurized gas or steam as it exits a pipeline. Pressurize air can have a very high flow and velocity as it leaves a pipe. This creates unsafe noise levels and could potentially lead to noise-induce hearing problems. Steam vent silencers reduce the elevated gas and steam pressure created by machinery, and eventually diffuse the flow to the atmosphere. These silencers are typically used in oil and gas processing, chemical processing, and heat recovery steam generators or boilers. They are also common in high pressure vents, safety relief valve outlets, steam vents, and system blow downs.

Combination Silencers

Combination silencers incorporate elements from several different types of industrial silencers to create a custom noise control solution. These industrial silencers may use both scattering and absorption to attenuate sound and bring noise down to an acceptable and safe level. These silencers are more effective than a frequency shifting silencer, however, as they are tuned to target a specific tonal noise. This process targets problematic frequencies and can reduce tonal spike, which also reduces the overall noise created by the fan exhaust. Combination silencers are installed in the gas path of a fan and are often used in conjunction with an absorptive silencer to provide additional attenuation. These silencers are custom designed by our skilled experts at SVI Industrial to ensure that your manufacturing facility complies with all noise regulations and operates at a noise level that is safe for your employees.

Choosing the best industrial silencer for your manufacturing facility depends on several factors, as each silencer type is best suited for specific projects. You need to consider the desired application of the silencer and the mandated noise regulations in your area.  For further information on the different types of industrial silencers, contact SVI Industrial’s team of skilled professionals. We look forward to helping you meet your industrial silencer needs.

Four Types of Industrial Silencers Used for Noise Control infographic