Understanding Diesel Generator Exhaust Silencer: Different Types and Sound Ratings

There is a common idea that diesel generators are noisy. It cannot be denied that diesel gensets produce more noise than other kinds of power generators, which could be a nuisance for residents around. Luckily, there are many ways to make the generators quieter. An exhaust silencer can effectively reduce noise and exhaust emissions produced during combustion. Read on and learn about different types of diesel generator exhaust silencers and the silencer sound ratings.

What is a diesel generator exhaust silencer?

A diesel generator exhaust silencer is a device for reducing diesel engine noise emission. It is inevitable that all internal combustion engines produce noise, more or less. The noise level will largely vary depending on diesel engine type. Diesel generators are powered by a diesel engine, which is an internal combustion engine that runs on diesel fuel. The operation of an internal combustion engine produces distinct pulses of exhaust gas that exit through the exhaust pipes and the muffler. Sound is a pressure wave formed from pulses of alternating high and low pressure air. Exhaust silencers are installed within the exhaust system of diesel engines. They allow the passage of exhaust gasses while restricting the transmission of sound.

What are the types of diesel generator exhaust silencers?

Diesel generator exhaust silencers come in different designs that vary depending on their size and shape, the way they work and a few other features. Commonly, the silencers are in cylinder, disc, and rectangle shapes, with inlets and outlets able to be located on both sides, both ends or one side and one end to work with your system. The three basic types are:

Reactive silencer

The internal construction consists of a maximum of three chambers connected by a tube. The exhaust noise created bounces between different chambers and reactive silencers mute sound by bouncing it around inside one or multiple chambers. This type of generator silencer is commonly used for low to mid-level noise reduction.

Absorptive silencers

The internal construction consists of fiberglass or E glass insulation. The exhaust noise is reduced as it flows through the insulation. This type of generator silencer has a greater sound attenuation rating and is typically used to reduce high frequency sound waves.

Combination silencers

As the name implies, this type of silencer combines the construction of the reactive and absorptive silencers. Combination silencers are typically made from a metal chamber with absorption material fitted inside. They can be used to reduce mid, low and high-frequency sounds.

The three basic designs mentioned above offer several different generator silencers that you can choose to meet your requirements. Which type of diesel generator exhaust silencer is right for you? It will depend on the model of your generator and the level of noise reduction you require. The following options are the type of silencers you can choose from:

Cylindrical silencers

Cylindrical silencers can be mounted horizontally or vertically, making them a great option for  generators of various different models. They are the most common used type of silencers and can be utilized in both inside and outside applications. Additionally, these silencers are relatively affordable and especially suitable for budget-minded shoppers.

Low-profile silencers

Low-profile silencers are available in various shapes such as rectangular, oval, and round. They  typically have a higher sound reduction rating than other types and commonly used in diesel generators located in sound attenuated enclosures. Please note that these silencers must meet the National Fire Protection Association (NFPA) guidelines. The downside of low-profile silencers is that they are more expensive compared to other options and may require more frequent maintenance.

Emission control silencers

Emission control silencers work by reducing the amount of noise generated by the engine. They absorb the noise and then redirect it away from the engine. Certain models of these silencers come with the ability to control the vibrations as well. The Environmental Protection Agency (EPA) regulates emissions for generators that supply main power to a facility. Emission control silencers can help filter emissions for better environmental control and to stay in compliance with local or EPA regulations. They are typically used in industrial settings where noise emissions need controlling.

Sound attenuation silencers

Sound attenuation silencers are specially designed to reduce the overall noise created by the diesel generator engine. These silencers absorb and dissipate the noise before it has a chance to reach the outside world. Diesel generators used in residential areas usually come in this type of silencer.

Hybrid silencers

Hybrid silencers combine both emission control and sound attenuation into one unit. These silencers are commonly used in places where both emission and noise reduction are strict requirements.

Sound ratings of diesel generator silencers

Sound pressure is measured in decibels (dB). A-weighted decibel (dBA or dB(A)) is an expression of the relative loudness of sounds as perceived by the human ear. Diesel generators with noise ratings are measured in dBA. Typically, noise ratings increase along with the power and size of the generator. For generators, a silencer does the same job that a muffler handles for engines in automotive and construction applications. Diesel generator exhaust silencers also come with a sound rating and they are divided into various grades.

Initially, the silencer ratings were divided into four basic grades: industrial, commercial, residential, and hospital grades. They were considered the industry standard in silencer manufacturing. During this period, the amount of sound reduction for grade varied between manufacturers. The Electrical Generating Systems Association (EGSA) came up with a rating guide that provided consistent silencer ratings for any manufacturer belonging to the association. The result was eight classes of ratings from Class 1 up to Class 8:

Industrial Grade – Exhaust noise reduction of 15 to 20 dBA

Residential Grade – Exhaust noise reduction 20 to 25 dBA

Critical Grade – Exhaust noise reduction of 25 to 32 dBA

Super Critical Grade – Exhaust noise reduction 30 to 38 dBA

Hospital Grade – Exhaust noise reduction of 35 to 42 dBA

Hospital Plus Grade – Exhaust noise reduction of 35 to 50 dBA

Extreme Grade – Exhaust noise reduction of 40 to 55 dBA

Super Extreme Grade – Exhaust noise reduction of 45 to 60 dBA

Manufacturers of generator silencers typically focus production on the grade and style combinations that customers demand the most.

All noise emitted by an engine does not specifically come from the exhaust system. In addition to the diesel generator exhaust silencer, there are many other ways to keep your generator quieter, such as moving the generator further away, using acoustic barriers like generator canopies and enclosures, installing acoustic wall panels, positioning anti-vibration mounts underneath the generator, using attenuators, etc.

Get a silent diesel generator today

If you are looking for a generator with exhaust silencer or other acoustic dampening devices, contact Dingbo Power today. We are a professional manufacture of diesel generator sets with almost 20 years experience in the industry. We offer a variety of silent type diesel gensets that can meet your needs. Feel free to contact us with any questions, concerns, or inquiries to learn more about the products & services we provide.