INCE-USA needs your help to select Nancy Timmerman Members’ Choice Project of the Year Award. This award was created to acknowledge notable project(s) completed in the field of noise control or architectural acoustics by an Associate or Full Member of INCE-USA.
The winning project will receive recognition of their achievement and visibility on INCE-USA materials, such as conference materials, website, and social media.
Voting for the award is now open to members through June 30. Please join us in selecting a winner.
A recently-completed building was fitted with a decorative roof screen fabricated from perforated sheet metal panels having “U”-shaped upturned flanges. When wind impinges on the panels, complex tone clusters are generated, leading to complaints from the occupants. After some preliminary (but inconclusive) field investigations, it was decided to test samples of the perforated panel in a large commercial wind tunnel where the speed and angle of the airstream could be controlled. Tones generated in the tunnel were found to occur in groups or clusters — these are most pronounced when the airstream’s angle of incidence is close to grazing. As the tunnel’s airspeed was adjusted between 8 and 12 meters per second, the principal tonal frequencies ranged between 800 and 1500 hertz. Gradually increasing airspeed caused the frequency of the tones to “jump” from one cluster to the next higher cluster. The physical principles of the tone-generating mechanism are not fully understood; however, it appears that structural resonances in the panel flanges are excited by air flowing over the perforate. Some form of a positive structural-aero-acoustic feedback loop is involved since a) the frequencies within each tone cluster are quite stable and, b) damping the panel flanges extinguishes the tones. After the building was retrofitted in 2020 with flange covers and inserts, field reports of tonal noise ceased altogether.
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Seattle City Light (SCL) constructed, owns, and operates three hydropower dams along the Skagit River, in Northern Cascades National Park (NCNP). Three reservoirs created by the dams are surrounded by Ross Lake National Recreation Area (RLNRA); NCNP surrounds the Recreation Area, and includes designated wilderness area, old-growth timber, and habitat for Northern Spotted Owl and other species of concerns. In support of the Skagit Hydropower Relicensing Project, relicensing application to FERC, SCL and HDR performed an extensive acoustical study. The study included 7-day unattended noise measurements at six locations in the study area, during peak summer recreation season, and springtime off-peak season. Those measurements included continuous acoustical and meteorological measurements, and continuous digital audio recordings. Measurement results and digital audio recordings were processed using National Park Service soundscape study methods, and included the determination of the percent of time anthropogenic noises were audible and also the calculation of the natural ambient sound level (Lnat). The final study report identified: CFI8X input data, powerhouse dimensions and spectral sound power levels for building exteriors, for transformers, switchyards, and corona noise; the average minimum heights of the transmission lines by segment; the mobile terrestrial noise source inventory; maximum pass by SPL for vehicles by pavement type and speed, ADT from 2017 – 2022; sound power levels and flow rates for dam spills; maximum spectral sound power levels for sirens and telephones; noise emissions from a bell on a locomotive occasionally rung by tourists; emergency generator noise emissions; the inventory of SCL-owned boats; the variable noise source inventory results; spectral sound power level for lawnmowing equipment; ambient noise measurement results summary; audio review summary, and; model validation results. Cadna-A noise modeling results were expressed using noise contours overlaid upon a terrain map of the study area
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