Sound science: Understanding and implementing generator set noise control

MANKATO, Minn.--(BUSINESS WIRE)--With the expanding use of diesel generator sets for emergency standby power, peak shaving and demand response, there has come an increased focus on controlling the noise these generators create. Whether generator sets are located in enclosures outside a facility, inside or on the roof, design engineers are making more efforts to control generator set noise and vibration in order to reduce the effects on neighbors and building occupants alike. And whether generator sets run continuously in prime-power applications, intermittently in demand response applications, or occasionally in emergency standby situations or testing, their operating sound levels may require remediation.

While local codes and zoning laws often require nominal noise reduction strategies, it is end users who are currently driving the demand for quieter generator set installations within available budgets. The cost to make modest reductions in noise is generally quite low, and generator set manufacturers have made the job easier by making engines that run quieter and with less vibration. In addition, a large aftermarket exists in advanced noise control solutions. However, the cost of noise control is not linear. The first 10 decibels (dBA) of reduction may be relatively inexpensive, but the last 10 dBA may be prohibitively expensive. That is why the current strategy in generator set noise control is to control as much noise as possible without losing control of the budget. This paper will examine the science behind generator set noise control and discuss a variety of solutions that will help consultants and design engineers achieve optimum noise control solutions.

What is noise?

Vibrating objects induce pressure waves that travel through the air and reach our ears as sound. Noise, by definition, is merely unwanted sound. When the amplitude of the pressure waves becomes too high, the amount of sound becomes uncomfortable. In addition to being annoying, excessive sound can cause permanent hearing damage. This is why the Occupational Safety and Health Administration (OSHA) established safety standards for workers exposed to loud noises. Local ordinances and zoning laws also establish rules regarding the amplitude of unwanted sound, but the standards are geared toward reducing public annoyance rather than promoting safety.

The human ear has such a wide dynamic range that the logarithmic decibel scale (dB) was devised to express sound levels in a convenient way. The ratio between the softest sound the ear can hear and the loudest sound it can experience without damage is approximately a million to one or 1:1x10⁶. By using a base-10 logarithmic scale, the whole range of human hearing can be described by a more convenient number that ranges from 0 dB (threshold of normal hearing) to 140 dB (the threshold of pain).

The full word document and high-resolution graphics are available for downloading from: www.cccinc.com/pr/mtuonsite/noise

About MTU Onsite Energy

MTU Onsite Energy is a leading producer of diesel-powered generator sets from 30 to 3,250 kW and natural gas-powered generator sets from 30 to 400 kW for standby, prime power and cogeneration applications. The company also provides automatic transfer switches, paralleling switchgear, controls and accessories for complete power system solutions. MTU Onsite Energy is a subsidiary of Tognum America Inc., part of the Germany-based Tognum Group.

www.mtuonsiteenergy.com

About Tognum America

Tognum America (formerly MTU Detroit Diesel) is a Tognum Group company and is responsible for the manufacture, sales and support of MTU and MTU Onsite Energy branded products in North and Latin America.

With its two business units, Engines and Onsite Energy, the Tognum Group is one of the world’s leading suppliers of engines and propulsion systems for off-highway applications and of distributed power generation systems. These products are based on diesel engines with up to 9,100 kilowatts (kW) power output, gas engines up to 2,150 kW and gas turbines up to 45,000 kW.

The product portfolio of the Engines business unit comprises MTU engines and propulsion systems for ships, for heavy land, rail and defense vehicles and for the oil and gas industry. The Onsite Energy business unit supplies distributed power generation systems carrying the MTU Onsite Energy brand. These comprise diesel engines for emergency power, prime power and continuous power, as well as cogeneration power plants based on gas engines and gas turbines that generate both power and heat. Tognum’s product portfolio also features fuel-injection systems built by L’Orange.

In 2011, Tognum generated revenue of around €2.97 billion and employs more than 10,000 people. Tognum has a global manufacturing, distribution and service structure with 24 fully consolidated companies, more than 140 sales partners and over 500 authorized dealerships at approximately 1,200 locations. Since September 2011, Engine Holding GmbH, a joint venture between Daimler AG and Rolls-Royce Group plc, has a majority holding in Tognum.