Noise Level Requirements Research Articles

Acoustic ceiling systems inside buildings: What we were taught and should now know instead

This presentation is an executive summary of how modular, suspended, acoustic, ceiling systems perform inside buildings as presented at meetings of the Acoustical Society of America and noise control engineering conferences between 2015 and 2022. It bridges the gap between laboratory testing of ceiling panel metrics and how complete ceiling systems perform inside buildings when combined with other building elements such as lights, air diffusers, floor slabs, plenum barriers and mechanical devices in the plenum. Ceiling system performance will be discussed from the perspectives of complying with minimum sound absorption, minimum sound isolation and maximum background noise level requirements in building design standards and guidelines. Corroboration with foundational testing conducted by the National Research Council of Canada and ASHREA will be integrated. Standards with prediction methods that should be used instead of ceiling panel metrics will be reviewed. Citations to studies will be provided for more detailed information.

Numerical Method for Modeling the Turbofan Engine Tonal Fan BPF Noise Generation and Propagation Accounting the SAS Complex Acoustic Impedance

Noise reduction issues in the developed world receive an increasing attention, which is reflected in a great tightening of the noise level requirements. For the practical solution of this problem authors propose a new high-performance numerical modeling method of three-dimensional tonal noise acoustic field generated by the fan as a bladed machine. The method is based on solving a boundary value problem for Fourier transformed convective wave equation with complex variables in a Cartesian coordinate system in the arbitrary domain with impedance boundary conditions by finite volume method. The noise source is set in the form of sound power on the surface near the rotor that bounds the area of the vortex perturbations (pseudosound). Sound power is determined by acoustic-vortex method. There are shown examples of the method validation and application.

You’re Going Where?

You’re Going Where?

Leadership in Energy and Environmental Design for schools: Designing mechanical system noise control to be green, affordable, and meet requirements.

Leadership in Energy and Environmental Design (LEED) for schools has added classroom acoustics (based on ANSI S12.60) to the prerequisite for all K‐12 schools seeking the U.S. Green Building Council LEED certification and several points for achieving additional measures. The Background Noise Level requirements of LEED for schools (U.S. Green Building Council) have several different compliance paths to meet the requirements. This paper explores the pros and cons of each and shares experience on how to design the HVAC noise system to meet the requirements for typical green building designs.

Installation Effects on the Flow and Noise of Wing Mounted Jets

T IS known experimentally, since the late 1970s, that a jet installed under a wing of an aircraft radiates more noise than the same jet in a standalone condition. The excess noise is the propulsion-airframe integration noise or commonly referred to as installation noise. When a jet is placed near a wing, there is an increase in noise in the flyover directions because of the reflection of sound by the wing. Here, installation noise includes not merely the noise increase due to the reflection of sound by the wing. The major part of this noise is generated aerodynamicly by the nonlinear interaction between the flow around the wing flap and the jet. In this work,ourprimaryinterestistomodelandtopredictinstallationnoise of aerodynamic origin. Installation noise increases not only the total aircraftnoiseinthe flyoverplanebutalsointhesidelinedirections.It is especially important during landings and takeoffs when the flaps are down. Duringthe1980s,anumberofexperimentswerecarriedouttrying to quantify the characteristics and intensity of installation noise [1– 4]. Most of these experiments involved the measurements of the jet alone noise and the noise when the jet was placed near a model of an aircraft wing inside an anechoic chamber. The experimental measurements by Wang [2] were the most systematic. In his experiment,ascaledmodelofthewingofaDC-10aircraftwasused. Large noise increase was observed in the flyover plane in the lowfrequencypartofthespectrum.Theincreaseinhigh-frequencynoise was less. In directions at small exhaust angles, the installation noise intensity was quite low. In the sideline, the radiated noise characteristics, on the other hand, were quite different. Overall, the measured data indicated that installation noise had a unique spectral shape and a directional pattern of its own. Recently, there is a renewed interest in propulsion-airframe integration noise. Mead and Strange [5] investigated the under-thewing installation effects on jet noise with special emphasis on the sidelinedirections.Theirinterestinthesidelinewasmotivatedbythe experience that it was generally more difficult to meet legislative limit on sideline noise level requirements. They reported the measurement of high installation noise level in the low-frequency range. One drawback of the Mead and Strange experiment [5], as well as most of the previous works, is that the experiments were carried out in static conditions. Upon realizing that the effect of forward flight is extremely important in the interaction between the flow around the wing flapandthejet,aseriesofnewexperimentsoninstallationnoise was conducted by engineers of The Boeing Company (Shivashankara and Blackner [6], Blackner and Bhat [7], and Bhat and Blackner [8]). They employed an open wind tunnel at M � 0:28 tosimulatetheforwardmotionoftheaircraft.Byusingellipticmirror microphones and the newly developed phase-array microphones, they were able to obtain noise source location maps as well as farfield noise data.

Evaluation of bio‐optical algorithms to remotely sense marine primary production from space

In situ bio‐optical measurements from several oceanographic campaigns have been analyzed to derive a direct relationship between water column primary production Pt ocean color as expressed by the ratio of reflectances R1 at 440 nm and R3 at 550 nm and photosynthetically available radiation (PAR). The study is restricted to the Morel case I waters for which the following algorithm is proposed: log (Pt) = −4.286 ‐ 1.390 log (R1/R3) + 0.621 log (PAR), with Pt in g C m−2 d−1 and PAR in J m−2 d−1. Using this algorithm the rms accuracy of primary production estimate is 0.17 on a logarithmic scale, i.e., a factor of 1.5. Using spectral reflectance measurements in the entire visible spectral range, the central wavelength, spectral bandwidth, and radiometric noise level requirements are investigated for the channels to be used by an ocean color space mission dedicated to estimating global marine primary production and the associated carbon fluxes. Nearly all the useful information is provided by two channels centered at 440 nm and 550 nm, but the accuracy of primary production estimate appears weakly sensitive to spectral bandwidth, which, consequently, may be enlarged by several tens of nanometers. The sensitivity to radiometric noise, on the contrary, is strong, and a noise equivalent reflectance of 0.005 degraded the accuracy on the primary production estimate by a factor 2 (0.14–0.25 on a logarithmic scale). The results should be applicable to evaluating the primary production of oligotrophic and mesotrophic waters, which constitute most of the open ocean.

Vibration and Noise Reduction in a Multi-Balanced Compressor.

A rotary type compressor used for air conditioning has been developed to satisfy very low vibration and noise level requirements. This paper describes the design technique for reduction of vibration and noise. Since vibrations in the compressor are mainly rotor unbalance vibrations due to the eccentricity of the rotary piston and the rotor bending flexibility, three plane balancing method is introduced instead of conventional two plane balancing method. The introduced balancing method is very effective even if bearing conditions vary. Owning to the 3 plane balancing, the developed compressor vibrations are successfully suppressed by 40% compared to the current compressor type. Noise reduction is also discussed with respect to silencer configurations installed in a compressed gas charge room. A new silencer structure is carefully designed with consideration of acoustic vibration mode shape of the room. According to the increase of the insertion loss of the silencer, the noise extremely reduced by-11dB compared with current type of compressor.

The Valsan 727‐200RE—A FAR part 36, stage 3, re‐engining program

Boeing 727‐200 airplanes powered by three Pratt & Whitney JT8D low‐bypass ratio turbofan engines contribute much of the noise annoyance around most of the world's airports because of the high level of jet exhaust noise produced during departures and because of the high frequency of operations by the large number of 727‐200 airplanes that are in service. Valsan Partners is managing a program to remove the two fuselage‐mounted JT8D engines from 727‐200 airplanes and replace them with newer higher‐bypass‐ratio JT8D‐200 Series engines installed within new nacelles. A special internal‐mixer nozzle is installed within a new acoustically treated tailpipe on the existing JT8D center engine. Re‐engined 727‐200RE airplanes produce significantly less noise during departures and also during landings. Cruise fuel consumption is also improved. Noise certification tests demonstrated compliance with the stage 3 noise level requirements of FAR part 36 as well as the chapter 3 requirements of ICAO Annex 16. The re‐engining modification and test results will be described.

Community Noise Levels of the DC-10 Aircraft

The results of recent flyover noise tests show that the McDonnell Douglas DC-10 aircraft powered by General Electric CF6-6D engines is much quieter than the current jet transport aircraft powered by turbojet or low-bypassratio turbofan engines. Several major design features incorporated into the engine and the installation of the engine on the aircraft have accomplished this reduction in noise. The DC-10 will meet the noise level requirements established by the Federal Aviation Administration for new transport aircraft and will, in fact, generate noise levels which are well below the requirements for takeoff and sideline noise. It will also meet the noise level requirements established by the Port of New York Authority and other airport operators at specific noise monitoring stations for normal aircraft operations. The DC-10 represents a major step in the direction of reducing noise pollution in communities around airports.