& A Enterprises, Inc. Noise and Vibration Control
Salem, MA 01970
01 + 978-741-1551
services relevant to noise and vibration control fall into several
catagories ranging from simple review and comment on an existing
design to a full array of design, analysis and precision measurment
services. Because the needs of a client will vary with their
experience base, so does the level of service offered by J&A
recognise that a dedicated noise control engineering staff is
beyond the resources of most companies. The engineers at
J&A Enterprises are accustomed to working in functional teams
on a project-by-project basis. As we routinely participate
in diverse projects, we can bring a new perspective and innovative
solutions to even the most intractable noise and vibration issues.
noise and vibration specifications requires the application of
good engineering practice. A design review can identify
potential problem areas in the earliest stages of a project.
The sooner in the design/build process a problem is identified,
the less costly the solution.
Enterprises offers a wide range of engineering services including
first task in any project is the definition of specifications
to be satisfied. We have found that noise and vibration
issues often receive inadequate attention during the early phase
of a project. Quantifiable specifications for noise and
vibration now can prevent misunderstandings later.
Enterprises is committed to leveraging technology to meet the
needs of our clients. We maintain workstations for computer
aided engineering and design. We routinely work in a
wide variety of formats ranging from two dimensional layouts
to full featured solid models. Chances are, we can work
seamlessly within your preferred CAD format.
56M European built mega yacht was recently delivered with
annoying generator noise levels, and an unacceptable "rumble"
noise in the lower deck aft cabins. Two different noise consultants
completed sea trials and made ineffective recommendations
before J&A was called. J&A correctly diagnosed the
problem as a very unusual structureborne noise related to
vibrations of the shaft system and thrust bearing. The vibrations
stemmed from the coincidence of a torsional resonance, causing
unsteady propeller thrust forces to drive the resonance of
an axial vibration mode involving the shaft, thrust bearing,
and the bearing's foundations. The J&A theory was validated
with a finite element analysis of the propeller shaft and
ship's structure, and further confirmed with a brief sea trial
to validate the measurements. J&A proposed a solution
to the rumble noise by simply shifting the location of a flexible
shaft coupling and also stiffening the thrust bearing foundation
using steel box-beams and PLEXUS adhesive. When that work
was being done, the shipyard also installed a J&A designed
improvement to the generator isolation mounts. Both projects
were successful. The generator can no longer be heard while
the yacht is at anchor, and the rumble noise in the cabins
was attenuated to an acceptable level.
Enterprises can analyze your design using proprietary and commercial
software tools. The variety of methods employed at J&A
ensures that an appropriate level of technology is brought to
bear on every project. Our analysis techniques range from
the relatively simple practices recommended by the Society of
Naval Architects and Marine Engineers to state-of-the-art dynamic
finite element analysis using the latest version of MSC/NASTRAN.
Enterprises can accurately measure noise and vibration characteristics
using a variety of equipment. We can measure overall noise
levels, or provide more detailed information such as noise and
vibration levels in 1/3 octave and narrow frequency bands.
Other measurements employed by J&A to investigate the physical
behavior of systems include frequency response, transfer function
estimation, system identification and decay rate estimation
(including room reverberation time).