Anechoic recordings of balloon bursts were systematically acquired for various conditions of balloon diameters, puncture location, and inflation pressure. The recordings were analyzed to derive the average frequency spectrum over the effective duration of the acoustic impulse. Although the data show the well-known limitations for the impulse responses (in terms of repeatability and directional behavior) when viewed at high resolution, the results are quite consistent when averaged over one-third octave bands and reveal that the diameter factor (the ratio between the diameter of the inflated balloon to that of its stated maximum), rather than the overall diameter of the balloon, is a good indicator of the sound pressure level, especially above 200 Hz. The study proposes some simple empirical formulas to predict the quantitative sound pressure level and the qualitative spectral response (using the spectral centroid & skewness) from balloon bursts, based on the inflation factor as a variable. The study also offers suggestions to maximize the value of the balloon-burst methodology in building acoustics measurements by describing an effective way to measure reverberation time while simultaneously acquiring useful directional information associated with the reflected sound.
A comprehensive noise study to define the soundscape of the city of Lincoln, NE, has been undertaken by the students enrolled in the Acoustics Program at Columbia College, Chicago. The study includes (1) a global review of best practices in the field of environmental noise control using a perspective emphasizing close attention to effective and proven solutions that can be implemented via policies and effective legislation, (2) the creation of a large-scale outdoor noise propagation computer model that incorporates all primary traffic arterial and readily identifiable noise sources, (3) a comprehensive large-scale testing of noise levels using specially modified noise dosimeters allowing for determination of Leq, and Ldn over 24-h intervals, and (4) a large scale attitudinal survey of the population using a web-based survey engine that allows for the geographical location of the respondents. The results of the survey are used to refine the density of the test locations and the scale resolution of the software model, as well as to provide city and county officials with a targeted course of action pertaining to regulations and noise abatement policies. The project is expected to last 3 years with up to 1200 test locations being analyzed.
A study was conducted to investigate the relationship between preferences in automobile exhaust noise and the demographic factors of a listening jury. Noise samples of four different vehicles were recorded at idle as well as at 3000 RPM, and 1/3 octave sound spectra were acquired simultaneously. The recordings were presented to the jury using headphones and a preference survey was administered. Zwicker loudness was computed for all samples. Demographic factors such as gender, age, current and future vehicle ownership, were correlated to listening preferences, and unforeseen results were found, especially in regards to sport utility vehicles (SUV).
An education in acoustics and noise control is traditionally provided by engineering and/or graduate schools; however, since its inception in 1998 the Acoustics Program of Columbia College Chicago has graduated 99 students with a liberal arts background; 71 were hired by consulting firms in acoustics & noise control and by manufacturers, 65 are still employed in the field, 8 went on to graduate school, and 1 was recently voted into the “40 under 40” list of outstanding professionals by Consulting Specifying Engineer Magazine. Our program currently offers 14 undergraduate courses in acoustics and it draws upon the college’s resources for calculus, physics, technical writing, management, accounting, architecture, and programming courses. We are in the second year of a scholarship program with the Institute of Acoustics at Tongji University, and we recently hosted the Highway Traffic Noise seminar from the National Highway Institute. Besides well-equipped test laboratories and a very wide array of computer modeling tools, a vinyl album cutting lathe was recently added to the program’s inventory and starting in 2010, our students will be required to demonstrate that they have the skills to prepare for, schedule, and execute a very complex task that leaves no room for errors.
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