BAC - Quiet Product Design

Noise Control Design for Industrial Equipment

In the design of complex pieces of machinery, noise control is often only one of many considerations. Therefore, noise control must compete for attention with other aspects of the design. However, awareness of noise control requirements can be promoted and maintained early on in the design process. In this way, many problems and pitfalls, such as costly retrofits, can be avoided, and confidence in the success of the design is assured.

Systems Design

As with many aspects of machinery design, noise control works best when integrated into the design process using a systems approach. A key factor in this approach is to include noise specification criteria in the overall functional requirements. With noise goals established early in the design process, each component part of the system can be evaluated for its performance with respect to noise.

Each machinery component which is a potential noise contributor must be studied in detail to understand and establish:

The magnitude of the noise problem.
Candidate noise control methods.
Predicted noise control effectiveness.
Design cost, life and maintainability.

In addition, each proposed solution for the component detail design must be evaluated for its effect on the performance of the system as a whole. Again, as with other design requirements, several iterations may be necessary until an acceptable solution, from the consideration of both detail and systems design criteria, is obtained.

Therefore, the initial assessment of the noise impact of the proposed test stand designs will be completed no later than the Preliminary Design Review. This will allow meaningful action to be taken toward meeting noise goals during the remainder of the design process, continuing on into the manufacturing planning, build and acceptance test phases of the program.

Functional Requirements

The functional requirements for the machinery with regard to noise will be given by a noise specification. This specification may be defined based on the benchmarks established with the manufacturer and its customer for operator environmental working conditions, which promote a high level of quality, performance and productivity.With established requirements, the noise control design procedure is straightforward. The designer need only determine the noise output of each potential contributor in order to calculate how much noise reduction will be needed to meet those requirements. Then the designer can select the area which may be most effectively treated, either the source itself, the transmission path, or a combination of both, and determine the noise control technique to be applied. The designer then moves on to the next potential source. The treatment of all noise sources must be designed such that their sum noise contribution is below specification limits, with an adequate margin of safety.

Potential Noise Sources

The primary sources of noise which are expected for the proposed test stands may be divided into several groups. One group may include various hydraulic components. These may be intense noise producing components, such as high flow orifices, valves and pipes. Another group of potential noise sources includes the pumps, drive motors, and other rotating components which may be associated with the equipment.

The design of these components could be optimized for lower noise emissions. Each component used in the machinery design must be evaluated, to determine the most effective noise control treatment method to be applied. Alternatively, the equipment enclosure itself may be used to reduce the noise which reaches the operator.

Noise Control Techniques

The techniques used to control machinery noise generally fall into the categories of vibration isolation, related flow velocity reduction or smoothing, and noise enclosures.Each presents its own design challenges.

Vibration isolation techniques focus on the mechanical vibrations which induce noise from the vibrating source component itself, or from another part of the structure connected to that component. The sources of vibration common to industrial equipment include unbalances in rotating machinery components and hydraulic fluid pulsations and turbulence caused by pumps and valve orifices. Reduction of equipment vibration not only decreases the noise produced, but usually improves the useful life and maintainability of that component, as well.

Enclosures are used to block the transmission path of airborne noise between the source and the operator. Proper design of an enclosure must address the mechanics of noise transmission in the selection and arrangement of materials, including the avoidance of any resonances within the operating range of the source equipment. Finally, good design also includes consideration of the manner in which the operator of the machinery must perform the required tasks, so that the enclosure does not impose a burden to the work process.