Page 35: of Maritime Reporter Magazine (March 1973)

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Noise Control On Diesel Tugs

Subject Of Meeting Held

By SNAME Pacific NW Section

The Pacific Northwest Section of The So- ciety of Naval Architects and Marine Engi- neers met at The Wharf, Fisherman's Ter- minal, in Seattle, Wash., on January 11, 1973.

During the technical session, following cock- tails and dinner, the members and guests heard a paper on "Noise Control on Diesel Tugs."

Diesel powered tugboats tend to be noisy. Not only are diesel engines inherently noisy, but tugs pack a great deal of power into a relative- ly small hull. Furthermore, the trend is toward more power and higher speed, and therefore, noisier engines. The problem is even more acute since the awareness of the harmful features of noise :has increased. The Government (Walsh

Healy Act) is specifying maximum noise lev- els, and crews are objecting to excessively noisy conditions. Owners, builders, and naval architects are becoming aware of the problem and are looking for solutions.

The paper "Noise Control on Diesel Tugs," jointly presented by Thomas R. Dyer of Mar- co, Seattle, and Bertel Lundgaard of Diehl and

Lundgaard, Bainbridge Island, contributes substantially toward the goal of quieter tug- boats.

The basic sound measuring unit is, of course, the decibel. Two terms requiring definition are sound absorption, and noise barriers. Noise 'barriers are used to prevent noise from travel- ing from the noisy to the quiet space. The ef- fectiveness of a noise barrier is a function of its mass.

On the other hand, absorptive materials are soft in order to allow the sound to pass through them rather than being deflected. Absorptive materials are therefore ineffective sound stop- pers.

The authors define one more term—frequen- cy. High frequency attenuation is much easier to achieve than low frequency attenuation. This is fortunate since high frequency noise is the most annoying as well as being the most severe threat to health.

Taking part in the meeting, left to right: Thomas R. Dyer of Marco, Seattle, and Bertel Lundgaard of Diehl and

Lundgaard, Bainbridge Island, co-authors, and George D.

Salisbury, chairman of the Pacific Northwest Section.

The construction at Marine Construction and

Design Co. of two sister tugs, the Edith Love- joy and the Anne Carlander (Puget Sound

Freight Lines) afforded the authors a unique opportunity to compare two differing noise control specifications on two otherwise identical vessels.

Fabreeca and rubber were used to isolate the main engine and certain other equipment from the hull proper. Various types of insulation, in- cluding Cafco Heat-Shield and an acoustic in- sulation consisting of two layers of foam separ- ated by a lead septum, were used in the engine room, as well as in the crew spaces.

The audience was shocked upright when Mr.

Lundgaard and Mr. Dyer, equipped with a noise measuring device and an ancient fog- horn, originally carried by either the Foss No. 9 or the Virginia V, demonstrated and identi- fied various noise levels.

Discussors were Paul Graebke of Puget

Sound Freight Lines; Robert Allan of Robert

Allan Ltd., Vancouver, British Columbia; S.R.

Windsor; Robert Kienholtz; and Howard

Lovejoy of Puget Sound Freight Lines.

March 1, 1973 43