Generic vibration criteria for nanotechnology experiments

Electron beam-based instruments are sensitive to the environment in which they operate. Adverse environments may limit their achievable resolution. Many equipment manufacturers provide specifications for the acceptable level of various environmental conditions, such as vibration, EMI, and acoustic noise. However, the quality of the specifications vary significantly, from well-defined to conjectural. Additionally, during the design of a facility, the specific instruments that will be used may not yet be known. Thus, it is useful to have "generic" criteria, intended to represent entire classes of instruments, to use in the design of facilities. Generic vibration criteria exist to aid in the design of laboratories, though there have been no such instrument-based generic criteria available for acoustic noise. The generic noise criteria that are currently used in lab design (NC, NR, dBA, etc.) were established to address the effect of noise on human beings. Using noise specifications for a significant number of instruments with varying resolving powers, correlation of resolution with environmental noise is demonstrated. Based on the data reviewed, generic noise criterion curves have been developed and presented for use in the design of facilities that contain noise-sensitive equipment. These are applicable when other well-defined and specific criteria are not available.

It is known that moderate levels of very low-frequency noise (less than 20 Hz) can induce vibration in elements of common residual housing structures. Measurements of low-frequency noise caused by nearby large industrial facilities were made at several different types of houses. These data are compared to criteria for the perceptibility of noise-induced vibration. The subjective perception by residents of house vibration, and the independent observations of others, correlate well with the noise criteria. In addition, measurements of house vibration were made at some test locations and are compared to both noise and vibration criteria.

Noise control in the offshore industry introduces novel problems to the oil industry. The major differences between offshore and onshore noise control are discussed, and the concepts of noise control in terms of direct sound from the equipment, the reverberant noise introduced when the equipment is enclosed in a module, and problems of structure-borne noise are developed and illustrated with examples. INTRODUCTION In recent years the oil industry has been concerned with the problems of hazardous noise levels on process plants and the effects of the noisy plant on its neighbors. This has resulted in considerable advance in design for noise control in the industry, and plants are now in operation in which noise levels are acceptable both on and in the neighborhood of the plant. However, the installation of fixed production platforms to develop the oil and gas fields in the North Sea has introduced novel noise control problems to the oil industry. It has become apparent that the personnel manning these platforms are not prepared to accept the high noise levels associated with this type of operation, and appear to be more concerned with this than the personnel engaged on mobile drilling installations. Following on from work in the onshore industry, Acoustic Technology has undertaken and is currently carrying out several design studies in the noise and vibration aspects of offshore platforms, and the concepts involved are outlined in this paper. DIFFERENCE BETWEEN ONSHORE INSTALATION AND OFFSHORE The major differences between onshore petrochemical plants and offshore platforms that affect noise levels are summarized below.(Available in full paper) These differences mean that a totally different approach to offshore noise control is required, and this approach must encompass path air- and structure-borne noise. While structure borne noise is ultimately perceived as an airborne signal, and consequently may not be subjectively distinguished from air-borne noise, its quantification is more easily dealt with separately - notwithstanding, of course, the fact that ultimately the sources will add together and must not jointly exceed the preset criterion for air-borne noise. SPECIFICATION OF NOISE CRITERIA In Europe there are no universal statutory limits for workers exposed to high noise levels. However, in Britain the Dept. of Employment has issued a Code of Practice recommending a maximum noise level to which workers should be exposed. This level is 90 dBA, or roughly Noise Rating curve 85 (NR 85), for a 40-hour week exposure. Furthermore, it is likely that this level will be incorporated into the Factories Act, and therefore it will become a statutory undertaking for employers to "take all reasonable means" to ensure that the noise levels are not exceeded. It is also likely that a similar regulation will apply to fixed production platforms in the near future. This level, of course, relates only to a maximum permissible noise level in order to reduce the risk of hearing damage. It does not purport to exclude it, or indeed create an acceptable environment for any specific task.

Beech 1900D flight test to characterize propeller noise on the fuselage exterior

The design of vibration-sensitive advanced technology facilities generally involves considerable attention to structural and mechanical aspects. In most cases, the vibration control measures contribute significantly to a facility's cost. The selection of a vibration criterion for use in design is an important step in the design process. Many process equipment manufacturers have provided tool-specific criteria, and the literature contains several forms of "generic" criteria. Unfortunately, there is no standardization in either tool-specific or generic criteria, and considerable confusion can arise, often due to the forms of data representation used. This paper first reviews some of the relevant fundamentals of signal processing, then uses experimental data to develop a tool-specific vibration criterion for an optical microscope. Two dissimilar approaches to generic criteria are discussed, and their signal-processing requirements are examined. They are compared with a manufacturer's published vibration criteria for a projection aligner. Recommendations are given for future development of tool-specific criteria.

The NASA Langley Research Center has completed a comprehensive research program that resulted in the development of a generalized model for estimating passenger discomfort response to combined noise and vibration. This model accounts for multiple frequency and multiple axes of vibration as well as the interactive effects of combined noise and vibration. The model has the unique capability of transforming individual components of a noise/vibration environment into subjective comfort units and then combining these comfort units to produce a total index of passenger discomfort and useful subindices that typify passenger comfort within the environment. This paper presents an overview of the model development including the methodology employed, major elements of the model, model applications, and a brief description of a commercially available portable ride comfort meter based directly upon the model algorithms. Also discussed are potential criteria formats that account for the interactive effects of noise and vibration on human discomfort response.

The vibration criterion (VC) curves, commonly used in the design of facilities which house vibration-sensitive instruments and tools, were developed by the author and his colleagues, in the early 80's, published by SPIE in 1991 and by IEST in 1993. Each of the criterion curves A through E is associated with a 'line width' or 'detail size' which was an attempt by the authors to describe the capabilities of the tools with which each curve might be associated. In the years since the curves were developed there have been substantial developments in tool design and isolation. In this paper the curves are reviewed in the context of present-day tools and processes. Changes are proposed where these might be justified.

It is sometimes necessary to improve the footfall performance of an existing concrete floor in a manufacturing facility, as is the case when the vibration criterion changes because of new technology. The paper examines two case studies in which the floors were modified simply by placement of an additional concrete slab atop the existing slab. This approach has some drawbacks, most notably the additional weight, which must be accommodated by the available framing and foundation capacity. Measured data are presented which illustrate the changes in structural properties and footfall performance.

This paper proposes a measurement system to assess the effectiveness of sound-insulating multilayers against structure-borne excitation, meant to complement the well-known and established systems used in the automotive field for airborne excitation. The system consists of a shaker, a frame connected to it and a plate clamped along its edges to the frame. When the frame is put into vibration by the shaker, the plate radiates noise into a small anechoic cabin where microphones are positioned. This layout intends to mimic the noise radiation from an automotive body panel. The development of such a system, in spite of its simplicity, presents non-trivial aspects, such as the design of a frame sufficiently rigid not to have modes in the frequency range of interest and the definition of a metric to evaluate the effectiveness of an acoustic multilayer in a robust way based only on SPL measurements. The paper describes how these challenges were overcome, using topological optimization to design a frame made with magnesium suitable for tests up to about 1kHz and FE simulations to define a robust assessment metric by placing the receiving microphones at a fixed distance from the plate and at positions corresponding to integration Gauss points. Besides the design, the paper describes also how the system was prototyped and eventually validated.

Dual-chamber pneumatic spring vibration isolation tables are commonly used as the base of precision equipment to isolate vibrations from the floor. During the design of dual-chamber pneumatic spring vibration isolation table, transmissibility is often taken as the performance measure, which does not represent the precision requirements directly and could not be adapted to different floor vibration conditions. In this article, a new performance measure is developed to obtain an optimum isolation performance during the design of a dual-chamber pneumatic spring vibration isolation table. Based on the generic vibration criteria, the weighted root-mean-square velocity of platform vibration in one-third octave bands resulting from the floor excitations is used as the new measure. The platform vibration is predicted by establishing a model of dual-chamber pneumatic spring vibration isolation table, which consists of a platform and four dual-chamber pneumatic springs. The model disturbance inputs are actual random floor excitations (7.98 µm/s, vibration criteria-C level), which are obtained by vibration acquisition test in a typical laboratory. The genetic algorithm is applied to solve this nonlinear optimization problem. The maximum weighted root-mean-square velocity of platform with the optimum design isolation table decreases to 2.35 µm/s, which provides a vibration criteria-E level environment.

The article presents achievement analysis of diagnostic criteria for assessing the quality of emergency and specialized medical care, in which, 62 patients of a therapeutic profile were admitted to the hospital. The general criteria was approved by the order of the Ministry of Health of the Russian Federation No. 203n of 10.05.2017, in terms of the volume and timeliness of care. Research results of the compliance of the provided EMА with the criteria for assessing its quality are: in the group of general quality assessment criteria — 1 00% and volume assessment criteria — 9 9,0% and timeliness — 9 8,9%. EMА at the admission of patients with a therapeutic profile to the hospital indicates a high level of its achievement.

With the increasing number of fire incidents, efforts are being made to quantitatively evaluate the egress safety of buildings. In particular, studies that reflect the behavioural characteristics of occupants when evaluating egress safety are being conducted. However, the research on the performance design and safety evaluation of facilities where individuals vulnerable to disasters (i.e. those who have difficulty evacuating in the event of a fire) reside remains insufficient. In this study, fire evacuating simulations were performed on welfare facilities for disabled individuals with mobility issues, and the egress safety was evaluated. The fire simulations were performed using the capacity of the smoke exhaust system as a variable. Meanwhile, the variations in temperature and toxic gases according to fire duration were analyzed to calculate the available safe egress time (ASET). The egress simulations were performed using the egress delay time and the number of egress guides as variables. Then, the required safe egress time (REST) was calculated. The results show that increasing smoke exhaust system delays the attainment of tenability limits, improving ASET. Egress simulations revealed an optimal number of egress guides. Based on these findings, general criteria have been developed to assess egress safety, considering the building floor area, smoke exhaust capacity, and occupant numbers. These criteria can be applied to ensure efficient and economical safety designs for typical welfare facilities for the disabled.

As human activity in the oceans has grown and scientific understanding of underwater noise has increased, it has been generally accepted that the growth of anthropogenic noise in the ocean has acute, chronic, and cumulative impacts on marine species, most notably marine mammals who depend on sound for foraging, breeding, predator avoidance, navigation, maintaining social bonds, and environmental awareness /1/. Since it was noted that continuous anthropogenic noise in the ocean was primarily generated by shipping /3/, ship radiated underwater noise has gained increased attention. Further, there are certain ship types which require low underwater noise for its function, such as research vessel, seismic vessel and fishing vessel. DNV GL has been working on noise and vibration criteria definition, noise and vibration control, and measurement for shipping industry. DNV GL SILENT criteria, which are the first set for ship's underwater noise, are presented in this paper. To reduce the underwater radiated noise from ship, a thorough process will be needed to cover front-end design, detailed design, construction and verification. The DNV GL Noise and Vibration Control Program, which is developed based on DNV GL's 50 years' experiences in the field, is presented in this paper.

Case studies of the leadership in energy and environmental design (LEED) analysis of an elementary school, a high school, and a college academic building were conducted. The case studies included field measurements of reverberation times within core learning spaces, noise insulation class ratings of walls between classrooms and other rooms as well as between classrooms and the exterior, and noise from building systems. The field measurements demonstrated that reverberation times generally met the criterion as designed. The walls between classrooms and walls between classrooms and other spaces generally required improvements to meet the LEED criteria. Noise from building systems generally met the 0 EQ point criterion. Few if any rooms met the +1 or +2 point requirement without special acoustical design including reduced air velocities, adding silencers in supply and return ductwork and moving terminal boxes and fan coil units out of the classroom spaces. Rooms adjacent to the mechanical rooms also generally exceeded the 45 dBA criterion for background noise due to both sound transmitted through the walls and through short duct runs. The study shows that standard school construction practices will have to be modified to meet the LEED for school criteria.

A case study will be presented regarding vibration and noise control design for an existing heart hospital. Facility expansion within a crowded site necessitates sandwiching a suite of new cardiac catheterization laboratories between mechanical equipment rooms above and the hospital’s main ambulance driveway below. The facility expansion also includes cardiac computed tomography, magnetic resonance imaging, and nuclear imaging, plus cardiovascular care, treatment, and administrative support spaces. Procedure and support spaces can be disturbed by mechanical equipment noise and vibration and noise from ambulance siren. Cardiac procedure instruments and imaging can be disturbed by low frequency noise and vibration from building mechanical systems, ambulance traffic, and building occupants. Design criteria for permissible building vibration and continuous background noise will be presented along with relevant sources and bases. Measurement evaluation results for design will be contrasted with criteria. Measures incorporated in design to mitigate vibration and noise on catheterization laboratories will be discussed. Measures considered in design include structural floor “detuning” concepts, stiffened supports for catheterization laboratory C‐arms, mechanical equipment vibration isolation mounts, and floating concrete floor systems for mechanical rooms. If available, postconstruction spectral analysis measurements of building noise and vibration will be presented.