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Enhancement of computer program SPECTRAN to provide optional synthesis of 1/12 octave-band and critical-band spectra from 1/3 octave-band spectra

Description: This paper describes greatly enhanced version of the computer program SPECTRAN, which was initially presented in Paper No. 96-RA104.01, at the A&WMA 89th Annual Meeting in June 1996. The program has had three basic upgrades since that time. The first is provision of an option to use either batch-mode input from previously prepared data files or a {open_quotes}user-friendly{close_quotes} interactive input routine. The latter is primarily for first-time users and those having only one, or very few, spectra to process. The second improvement is the synthesis of 1/12 octave-band spectra from 1/3 octave-band spectra, with {open_quotes}tone correction,{close_quotes} in a manner similar to that used in the original version of the program. The third fundamental improvement is addition of a unique new capability to synthesize classic {open_quotes}critical-band{close_quotes} spectra from 1/3 octave-band input spectra. Critical-band spectra are also termed {open_quotes}equivalent-rectangular-bandwidth (ERB){close_quotes} and {open_quotes}equal-contribution-to-speech (ECS){close_quotes} spectra.
Date: July 1, 1997
Creator: Chang, Young-Soo & Liebich, R.E.
Partner: UNT Libraries Government Documents Department

Comparative review of available computer programs for modeling meteorological and terrain effects on long-range propagation of audible noise

Description: Assessment of the environmental impacts of audible noise produced by human activities -- such as construction and operation of industrial facilities, vehicular traffic, and aircraft operations -- requires the use of sound-propagation computer programs capable of predicting the sound-pressure spectra that will be produced by these noise sources at distances as great as 10 km. Under acoustically unfavorable meteorological conditions, such as ground-based temperature inversions and noise-sensitive receptors being located downwind from intrusive sound sources, audible noise levels can be increased, even on the order of 20 dB. This paper presents a brief overview of computer programs currently available (``operational``) for predicting the effects of such meteorological conditions on audible noise levels in a format that allows gross comparison of the relative capabilities of the programs from the standpoint of engineering application to environmental impact assessment.
Date: June 1, 1994
Creator: Liebich, R. E. & Chun, Kyong C.
Partner: UNT Libraries Government Documents Department

Estimation of environmental noise impacts within architectural spaces.

Description: Public Law 91-596, ''Occupational Safety and Health Act of 1970,'' Dec. 29, 1970, stimulated interest in modeling the impacts of interior noise on employees, as well as the intelligibility of interior public-address and other speech intra-communication systems. The classical literature on this topic has primarily featured a statistical uniform diffuse-field model. This was pioneered by Leo L. Beranek in the 1950s, based on energy-density formulations at the former Bell Telephone (AT and T) Laboratories in the years from 1930 to 1950. This paper compares the classical prediction approach to the most recent statistical methods. Such models were developed in the late 1970s and included innovations such as consideration of irregularly shaped (e.g., L-shaped) interior room spaces and coupled spaces.
Date: May 3, 2002
Creator: Chang, Y. S.; Liebich, R. E. & Chun, K. C.
Partner: UNT Libraries Government Documents Department

Development of computer program ENMASK for prediction of residual environmental masking-noise spectra, from any three independent environmental parameters

Description: Residual environmental sound can mask intrusive4 (unwanted) sound. It is a factor that can affect noise impacts and must be considered both in noise-impact studies and in noise-mitigation designs. Models for quantitative prediction of sensation level (audibility) and psychological effects of intrusive noise require an input with 1/3 octave-band spectral resolution of environmental masking noise. However, the majority of published residual environmental masking-noise data are given with either octave-band frequency resolution or only single A-weighted decibel values. A model has been developed that enables estimation of 1/3 octave-band residual environmental masking-noise spectra and relates certain environmental parameters to A-weighted sound level. This model provides a correlation among three environmental conditions: measured residual A-weighted sound-pressure level, proximity to a major roadway, and population density. Cited field-study data were used to compute the most probable 1/3 octave-band sound-pressure spectrum corresponding to any selected one of these three inputs. In turn, such spectra can be used as an input to models for prediction of noise impacts. This paper discusses specific algorithms included in the newly developed computer program ENMASK. In addition, the relative audibility of the environmental masking-noise spectra at different A-weighted sound levels is discussed, which is determined by using the methodology of program ENAUDIBL.
Date: March 31, 2000
Creator: Chang, Y.-S.; Liebich, R. E. & Chun, K. C.
Partner: UNT Libraries Government Documents Department

Development of computer program ENAUDIBL for computation of the sensation levels of multiple, complex, intrusive sounds in the presence of residual environmental masking noise

Description: The relative audibility of multiple sounds occurs in separate, independent channels (frequency bands) termed critical bands or equivalent rectangular (filter-response) bandwidths (ERBs) of frequency. The true nature of human hearing is a function of a complex combination of subjective factors, both auditory and nonauditory. Assessment of the probability of individual annoyance, community-complaint reaction levels, speech intelligibility, and the most cost-effective mitigation actions requires sensation-level data; these data are one of the most important auditory factors. However, sensation levels cannot be calculated by using single-number, A-weighted sound level values. This paper describes specific steps to compute sensation levels. A unique, newly developed procedure is used, which simplifies and improves the accuracy of such computations by the use of maximum sensation levels that occur, for each intrusive-sound spectrum, within each ERB. The newly developed program ENAUDIBL makes use of ERB sensation-level values generated with some computational subroutines developed for the formerly documented program SPECTRAN.
Date: March 31, 2000
Creator: Liebich, R. E.; Chang, Y.-S. & Chun, K. C.
Partner: UNT Libraries Government Documents Department