Any ship, particularly "workboats" (i.e. tugboats, research vessels, ferries) can be very noisy
places, ask anyone who works on one. Smaller vessels (60 to 300 feet) will have very high
horsepower machinery (diesel engines, pumps, large hydraulic systems) just feet away from sleeping
cabins, offices and control rooms. With noise control being such a critical factor for the marine
industry, NCE has become one of the leaders in the field of Marine Acoustics. We have provided
technical assistance on hundreds of vessels; designed by naval architects, built by shipyards or
operated by government and private organizations. NCE's staff has authored more than 50 papers on
shipboard noise, including the "Design Guide for Shipboard Airborne Noise Control", an industry
standard published by the Society of Naval Architects and Marine Engineers in 1983 and its
Supplement sponsored by the U.S. Coast Guard published in 2000.
Services offered to Naval Architects, Shipyards and Marine Operators are:
SHIPBOARD NOISE & VIBRATION ANALYSIS
NCE uses our own Designer-NOISE and other software
products/tools (many of which were developed
in-house), for the prediction of shipboard noise and vibration. Accurate noise predictions can be
performed based on a ship's general arrangement, typical structural details and machinery
arrangements and details.
STRUCTURAL ANALYSIS/FEA
NCE uses Finite Element Analysis (FEA) software to model structures such as masts, machinery
foundations, portions of the hull or full ship/superstructures. The FEA models are used to predict
structural natural frequencies to determine the existence of resonant conditions and also to
determine forced responses to known vibration inputs. NCE can also perform stress analyses. FEA
codes used by NCE are: NEiNastran, COSMOS/M and Maestro (from Proteus Engineering our partner in
Designer-NOISE).
UNDERWATER NOISE ANALYSIS
Underwater noise for non-military applications has gained significant importance in the last ten
years, particularly for vessels operating in environmentally sensitive areas. NCE has extensive
experience in predicting and controlling shipboard underwater noise levels. We use Designer-NOISE
to predict underwater noise levels by extracting hull vibration levels from the model and
converting those values to far-field radiated noise. NCE has extensive experience in the design,
construction and testing of quiet underwater vessels - both military and commercial. (See Noise
Control Treatment Design below).
SONAR SELF NOISE ANALYSIS
Sonar-self noise is the sound of a vessel's machinery that is picked up from the vessel's hull
mounted hydrophones. High self-noise interferes with optimally running sonar systems and NCE can
predict the levels of self-noise to be compared with a sonar vendor's specifications. In addition,
noise control treatments exist to mitigate such problems.
NOISE CONTROL TREATMENT DESIGN
NCE selects optimal noise treatments based on a comprehensive sound and vibration analysis
described above. These treatments include: vibration isolators (see section below), acoustical
insulation, damping, floating floors and silencers. Once treatments have been selected, NCE
provides material specifications, areas of coverage, installation guidelines, potential vendors and
noise reduction estimates. In this manner, adverse impacts on cost, weight, space and operation of
the vessel can be minimized.
MACHINERY VIBRATION ISOLATION
Machinery structureborne vibration is one of the biggest sources of noise in ships. One of NCE's
noise reduction approaches is to mount the offending equipment on vibration isolators. NCE selects
vibration isolators, reviews proper equipment mounting points, isolator characteristics, and
performs six-degree-of-freedom natural frequency calculations. During sea trials we measure the
vibration isolator's transmission loss (TL) or attenuation. NCE has collected data like this into
a database for various types of vibration isolators and equipment.
SHIPBOARD MEASUREMENT & DIAGNOSTIC SURVEYS
NCE is highly experienced in the measurement of shipboard vibration and noise. NCE has conducted
numerous noise and vibration tests on-site. Our extensive test experience includes airborne noise,
vibration testing, underwater radiated noise and sonar self noise. NCE's test equipment includes
numerous handheld instruments and a sixteen-channel data acquisition system which can be used for
ship-wide vibration surveys. NCE can also conduct diagnostic noise and vibration tests to
determine root-causes of noise and vibration problems. This includes determination of controlling
noise sources and noise transmission paths.
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