Noise News for Week of February 27, 2000

Oldsmobile Aurora Has Features That Make for Quiet Ride

PUBLICATION: Automotive Manufacturing and Production
DATE: March 1, 2000
SECTION: Vol. 112, No. 3; Pg. 64-66
DATELINE: Detroit, Michigan

Automotive Manufacturing and Production printed a review of the new 2001 Oldsmobile Aurora. Part of the review discusses features that make the Aurora's ride more quiet.

According to the review, to give the Aurora a quieter ride, the designers use rubber isolating elements that are fitted throughout the chassis. In addition, body cavities are filled with expandable baffles that muffle noise considerably. The dashboard is heavily insulated as well. There is a case foam carpet to reduce road noise from below, as well as more than twenty noise blockers that are built into the pillar and rocker panels and installed on the floor pan.

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Silencer Muffler Developed for Truck Engine "Jake" Brakes

PUBLICATION: Fleet Equipment
DATE: March 1, 2000
SECTION: Vol. 26, No. 3; Pg. 46-50; Issn: 07472544
DATELINE: Detroit, Michigan

Fleet Equipments reports on the benefits of engine brakes for the trucking industry. The Jacobs Vehicle Systems "Jake" brake is the most commonly used in the industry. Much of the article discusses the safety and technology behind "Jake" brakes. Part of the article is devoted to talking about the noise these brakes produce.

According to the article, the noise from engine brakes can increase vehicle noise by one hundred percent. The sharpness and harshness of the noise makes it particularly disagreeable. Exposure to the noise is also annoying to the drivers inside the truck cabs. Many towns have reacted by passing ordinances that ban the use of "Jake" brakes.

The article reports that the industry has reacted by creating the Donaldson Silent Partner. It is a device that is the result of a collaboration between Donaldson Company and Jacobs Vehicle Systems. It is a silencer that reduces acceleration noise and eliminates the sharp, harsh sound of engine brakes. It can be added on to existing mufflers. It does not increase exhaust back pressure or reduce a truck's fuel economy.

The article reports that a truck with a Silent Partner produces half as much engine exhaust noise as a truck equipped with a conventional muffler. Acceleration noise has been dropped by twenty-five percent. The harsh noise of the engine brakes is converted to a "warm, mellow exhaust tone." Fuel economy remains good. The Silent Partner has a warranted life of eight years or 1,000,000 miles.

The article lists the advantages of using the Silent Partner: "Engine brakes can be used more often, improving control and safety. Brake, tire and exhaust life is extended, reducing maintenance and downtime. A better in-cab environment improves driver productivity and satisfaction, which leads to less driver turnover and lower labor costs. Fewer noise -related complaints (and citations) will help improve the image of the trucking industry. A quieter truck is seen as a higher quality truck, which can translate into higher trade-in or selling prices."

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Benefits of Active Noise Reduction Headsets in the Workplace

PUBLICATION: Occupational Health and Safety
DATE: March 1, 2000
SECTION: Vol. 69, No. 3; Pg. 48; Issn: 03624064; Coden: Ohsadq
BYLINE: Irene Lebovics
DATELINE: Linthicum, Maryland

Occupational Health and Safety reports that workers who are routinely subjected to long-term, low-frequency background noise such as vehicles, machinery, engines, large compressors, and air conditioning units are suffering many adverse health effects, particularly hearing loss.

According to the article, active noise reduction (ANR) technology effectively reduces low-frequency noise, thereby protecting workers' hearing and improving their ability to communicate in their work environment.

The article explains that commonly-used ear plugs and ear muffs are passive noise reduction devices. These devices work best against mid- and high-frequency noises, but are not effective protection against low-frequency noise ANR technology, on the other hand, produces destructive interference to cancel one source of noise with another. An ANR headset contains a microphone in each earpiece that listens to incoming low-frequency noise and sends the information to a controller for analysis. The device then creates an inverse ("antinoise") acoustic output signal that cancels out the noise and eliminates it.

The article reports that low-frequency background noise also reduces the intelligibility of speech through a phenomenon called "upward spread of masking." As the noise increases, it becomes increasingly difficult to detect the high-frequency sounds that allow one to understand speech. When this happens, communications tend to be over-amplified, causing hearing damage and safety hazards that arise from not being able to understand what someone is saying. ANR is the only technology that reduces low-frequency noise enough so that speech can still be heard clearly.

The article recommends that ANR headsets be used in workplaces where communication between employees is critical. This greatly increases safety in the workplace.

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Benefits of Uniform Attenuation Hearing Protection in the Workplace

PUBLICATION: Occupational Health and Safety
DATE: March 1, 2000
SECTION: Vol. 69, No. 3; Pg. 50-54; Issn: 03624064; Coden: Ohsadq
BYLINE: Per Hiselius
DATELINE: Billesholm, Sweden

Occupational Health and Safety reports on the technical and scientific aspects of workplace noise and how it affects human hearing and communication.

According to the article, a better way to measure noise than just a decibel reading is to use 1/3 octave-band analyzers, which measure the level of noise present in each of many frequency bands. This allows a better determination of what types of hearing protection are most helpful for different noise sources.

The article reports that uniform attenuation hearing protectors are devices which are the most technologically superior at protecting hearing in the workplace. The devices are offered by a number of companies such as Bilsom, which manufacturers small, lightweight hearing protectors that increase the wearer's ability to understand speech.

The article states that scientists conduct tests such as the Modified Rhyme Test to evaluate different types of hearing protectors. Subjects are asked to identify sounds and words heard. Modified Rhyme Tests have shown so far that uniform attenuation hearing protectors provide the best speech intelligibility against low-frequency background noise, even with wearers who already suffer from some degree of hearing impairment.

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Next week: March 12, 2000



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