Knocking off the noise

1|,\NE of the major new areas of lfgovernment intrusion into the transportation of lumber and building materials is control of noise.

On April 15, 1975, new federal noise laws regulating the allowable amount of inteior noise (designed primarily to protect the driver's hearing) went into effect.It established an in-cab noise limit of 90 decibels and is effective on all trucks, regardless of age.

On October 15. 1975, the Environmental Protection Agency decreed new regulations concerning exterior noise. Basically, the EPA's nosie limit is 86 db(A) at 50' in zones posted at 35 mph or less. Above 35 mph, the limit is 90 db(A) at 50'.

Initially, enforcement of the new regulations were handled by the federal government, mostly through the Department of Transportation. Lately, more states are becoming involved and in at least one Western state, California, the state highway patrol has taken over enforcement activities. To increase compliance in the months since passage of the new controls, the feds have also stepped up enforcement. Scofflaws, please note.

Despite its unfamiliar terminolory, the terms decibels, dB, and the like are, basically, a measuring stick for the amount of sound heard or produced. The sounds we hear are atmospheric pressure variations. The greater the pressure, the louder the sound we hear. Sound pressure is measured in decibels (dB) which is a ratio or a

Story at a Glance

Both interior and exterior sound control for trucks becomes a greater concern for owners as enforcement of the new regulations gets tougher.

measured pressure. Generally, a decrease of 6dB will reduce the loudness by half.

One result of the new regulations has been to produce a new miniindustry to supply the materials needed to make older trucks meet the imposed limits.

Despite early fears that it would be too expensive to. retrofit some units, it appears mosi all can be brought into legal line within cost levels most truck owners can live with. One firm. Truck Acoustics, Canoga Park, Ca., developed a combination sound deadening and appearance package which reduces the in-cab dB(A) rating to well below the federal standards. Their initial instal' lations (on Freightliners) reduced the racket from 93 to 86 db(A), an 80% sound energy drop.

Mufflers have proven a problem area as many a l0 year old tractor, for example, has been modified so many times that it would be difficult, if not impossible, for manufacturers to produce a retro fit line of mufflers to fit every vehicle that ever rolled off their line.

Solving exterior noise excesses has proven a difficult and often a more expensive project than initially envisioned. Here again, noise consultants have set up shop to try and serve this new market created by government edict.

If after determining that one of your vehicles exceeds the limit, experts say the next step is to identify the sources of the problem and concentrate on those that are easiest and cheapest to repair.

Among the various vehicle systems that contribute to overall noise produced by operation are the exhaust system, air in-take, cooling system, tires and engine. Noise reduction is a science and quieting your truck(s) may prove more difficult to do yourself than you had imagined. As one of the representatives of the supersonic Concorde airliner, one of the noisier pieces of machinery around, recently remarked, "our bird would make noise moving through the air even if it had no engines." That tired old truck in your yard is no different.

The cost and difficulties of complying with the new laws can be slight or horrendous, but the rules are here to stay and sound control has become a permanent part of the cost of doing business.

Simpson redwood lumber is the naturally perfect building material. So don't be surprised wnen your customers keep asking for more in 1976. Architects and builders have discovered redwood's natural beauty and design latitude. And do-it-yourselfers have found that redwood's durability makes it the perfect building material for decks, fences, planter boxes and other yard and garden needs.

Simpson redwood lumber is available in a wide range of patterns, grades and sizes, tooso you can answer a variety of your customers' needs -whether it's an order for redwood 2x4's to build a fence or Ruf-Sawn V-joint Tongue and Groove redwood for siding a new townhouse complex.

lumber from Simpson Building Suppty Company. Give us a calltoday.

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SIMPSON BUILDING SUPPLY COMPANY

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