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With the advent and proliferation of computer technology, many design companies are creating and using computer modeling to determine noise control requirements for extensive installations such as petrochemical plants, cogeneration facilities, compressor stations, etc. However, in order to be effective these programs require correct input data on source characteristics such as source strength, frequency characteristics, directional characteristics, and temporal variations. This paper discusses the relative merits of the current methodologies used to obtain this data including manufactured supplied data, laboratory measurement methodologies, and field measurement methodologies. Current testing standard are also reviewed.

The mechanical response characteristics of the hand due to vibration directed into the hand by a vibrating handle was modeled as a three-degree-of-freedom, mass-spring-damper system for vibration in each of three mutually orthogonal directions. The coupling that existed between the three mass elements and the relative values of the different components of the mechanical model correlated very well with the actual coupling and the physical relations that exist between the different layers of tissues in the fingers and hand. The model indicated that the mechanical response of the hand due to hand-induced vibration was a function of the direction of the vibration relative to the hand and a function of the manner in which the vibrating handle was clasped. The model implied that vibration directed into the hand at frequencies below 100 Hz was transmitted through the different layers of tissues in the hand into the skeletal system and then up the arm. Vibration energy at frequencies above 100 Hz tended to be isolated to the tissued directly in contact with the vibrating handle.

In response to surging demand for increased electrical power, utilities and independent power producers are evaluating and installing large numbers of gas turbine driven generators. Often these are sited close to existing developments and have to meet stringent environmental guidelines. The primary noise source of gas turbine generators is generated by the power turbine and radiated from the exhaust stack. Most often this is controlled by use of a muffler and/or heat steam recovery boiler (HRSG). Due to the increasingly restrictive noise requirements and the desire for accountability, there is greater need to specify and evaluate the installed performance of gas turbine exhaust mufflers. The most appropriate performance specification, for the evaluation of mufflers, is ‘‘insertion loss’’ despite the difficulties that currently exist with its measurement and determination.