Volume 77, Issue S1, April 1985
Index of content:
- PROGRAM OF THE 109TH MEETING OF THE ACOUSTICAL SOCIETY OF AMERICA
- Session A. Noise and Coordinating Committee on Environmental Acoustics (CCEA): (1) Where Do We Stand on Standards on Noise? (2) Airport and Traffic Noise
- Invited Papers
77(1985); http://dx.doi.org/10.1121/1.2022215View Description Hide Description
This paper describes the principal organizations responsible for the development of noise standards, discusses processes through which they are generated, and identifies the principal types of standards that exist. The majority of standards are developed voluntarily by the private sector, both in the USA and abroad. The American National Standards Institute (ANSI) coordinates American federated national standards system which in acoustics includes professional societies such as ASA, SAE, and ASTM and industry organizations such as NEMA, CAGI, and OPEI. ANSI also is the U.S. member of the organizations responsible for developing voluntary international standards. Participation in the development of ANSI and international standards in acoustics is open to all who have a direct and material interest. Voluntary standards cover all aspects of acoustics, including measurement, instrumentation, propagation, noise control devices, and human response criteria. In the USA, government standards or regulations are promulgated by all levels of government, federal, state, and local. Participation in their development is determined by the rules appropriate to the promulgation entity. Other countries also promulgate regulations in which opportunities for comment by individual interested persons are usually announced in the USA. Government standards and regulations cover many major sources of noise such as transportation vehicles, and various environments such as noise in the community and in the workplace.
77(1985); http://dx.doi.org/10.1121/1.2022216View Description Hide Description
All four of the American National Standards Committees for which the Acoustical Society holds the secretariat are active in developing standards directly applicable to the workplace. S1 (Physical Acoustics) is involved with standards for equipment used to specify noise conditions including sound level meters and personal dosimeters. S2 (Shock and Vibration) has a joint interest with S3 (Bioacoustics) in standard procedures for describing human exposure to mechanical vibrations and shock. S3 has a major concern in standards relating to measurement of hearing loss and establishing the risk posed by occupational noise to hearing. S12 (Noise) is in the process of producing standard methods for measurement of noise in the workplace, evaluating hearing protectors, and evaluating the effectiveness of industrial hearing conservation programs. The status of these standards activities as well as others which directly or indirectly have an impact on problems of occupational noise is the subject for this presentation.
77(1985); http://dx.doi.org/10.1121/1.2022217View Description Hide Description
Standards for assessing the compatibility of various land uses with an acoustical environment have been a developmental goal of national and international standards producers for over 20 years. Acoustical Society publication of S3.23‐1980 was the first major accomplishment in these efforts. Related international standards are now emerging. A standard for use with high intensity impulsive noises is under development in S12. The evolution of these standards and their uses by regulatory agencies are discussed in this paper.
77(1985); http://dx.doi.org/10.1121/1.2022270View Description Hide Description
Meaningful noise measurements require more than the precise measurement of the sound level at some point in space at a particular instant of time. The additional considerations which apply to measurements of the noise emission of individual stationary sources fall into two categories: (1) Installation and operation of the source so that its noise emission is relevant to the purpose of the test. (2) Acquisition and processing of sufficient data to extract the information desired. The first category is the responsibility of industry‐specific sound test codes. Such test codes need not go into any detail concerning the acoustical measurements since these are covered by a coordinated set of ANSI Standards for which the Acoustical Society of America is responsible. The present paper provides an overview of the relevant ANSI Standards (and their ISO counterparts) in order to help the writers of a sound test code determine which part of the set is most appropriate for the particular type of source to be tested. The proper selection of a descriptor and other provisions of ANSI Standard S12.1‐1983 will also be discussed.
77(1985); http://dx.doi.org/10.1121/1.2022271View Description Hide Description
The ISO 3740 series of basic standards for the determination of the sound power levels of stationary noise sources was issued by the International Organization for Standardization during the 1970s. American National Standards based on the ISO 3740 series have now been completed. These measurement standards have been adopted by several industries, including the manufacturers of computers and business equipment whose test code is continuously updated to reflect improvements in instrumentation and measurement methodology. Two important problems currently being addressed are the quantitative assessment of prominent discrete tones and the characterization of impulsive noise. The new standards being developed by the computer and business equipment industry are discussed with reference to current national and international requirements.
- Contributed Papers
77(1985); http://dx.doi.org/10.1121/1.2022272View Description Hide Description
The Federal Aviation Administration's FAR Part 150 Airport Noise Compatibility Planning Program is an effective program that is on‐line and working. It establishes standard noise methodologies and units (L A, dBA, and Ldn ), establishes the Integrated Noise Model as the standard airport noise‐modeling methodology, identifies land uses normally compatible with various levels of airport noise, and provides for voluntary development and submission of Noise Exposure Maps and Noise Compatibility Programs by airport operators. An 8% set‐aside of airport grant funds is provided for development and implementation of the programs, including soundproofing as well as purchases of properties. After a slow initial start‐up cycle, 19 Noise Exposure Maps or Noise Compatibility Programs have now been submitted, and 11 maps and 5 programs have received approval. Federal grants have been issued to 19 airports to develop noise compatibility programs or to implement approved programs. Some 22 programs are expected to be submitted during fiscal year 1985. The FAA will hold a national planning conference in October 1985 to assess the program's future needs and directions.
77(1985); http://dx.doi.org/10.1121/1.2022273View Description Hide Description
A 1981 Air Force Draft Environmental ImpactAnalysis (DEIA) on converting Rickenbacker Air National Guard Base (RANGB, formerly Lockbourne Air Force Base) to a civilian air terminal operated by a new county port authority (RPA) indicated that the DNL increase would be insignificant. In 1982, residents of the central Ohio village of Groveport (1.7 miles from the landing threshold of RANGB Runway 22) showed in federal court that military air activity was not as noisy as modeled in the DEIA, ceased after 11:00 pm and did not resume until 8:00 or 9.00 am the next day. Noise monitoring near Dayton's Municipal Airport where Emery Air Freight operates found five hourly Leq's which ranged from 63 to 73 dBA and peaks from 74 to 94 dBA. For the same times, Groveport hourly Leq's were about 45 dBA with 50‐ to 65‐dBA peaks. The proposed civilian air cargo carrier projected 26 round trips per night by heavy aircraft such as the DC‐8 and the Boeing 727. Their night noises would be disruptive to sleep since not all houses had adequate noise insulation and aircraft noise abatement procedures could not be adequate. The court ruled that the Air Force EIA DNL values be made more accurate and RPA should promulgate a noise mitigation plan for Groveport's approval. Beyond feasible aircraft noise abatement procedures, the plan is that within the 90 SEL contour of the noisiest tenant aircraft and where night overflight noises in sleeping quarters exceed 55 dBA, residences shall be insulated or purchased by the RPA. Outside the 90 SEL contour, only houses where the interior noise peak exceeds 55 dBA an arbitrated number of times per night are included. Civilian air cargo operations have not started.
77(1985); http://dx.doi.org/10.1121/1.2022274View Description Hide Description
The future traffic noise generation from Trans‐European Motorways still under construction throughout Europe was analyzed in a study aimed to introduce standard noise controlsystems into the TEM Recommendations. Different prediction techniques developed by national institutions of nine countries were employed in computations of noise levels at 15 m from curbsides for varying traffic parameters. Comparisons between results relative to the procedures demonstrated that the USA method (FHWA) yielded about 5 dBA higher levels than European models especially in mountainous terrains and at higher percentages of heavy vehicles. Applying a statistical regression analysis, a simplified mathematical model for TEMnoise predictions was developed with a satisfactory correlation coefficient. A new combined parameter, T (u,s,n,h,g), corresponding to interrelated TEM traffic variables (volume, speed, number of lanes, heavy vehicle percentage, and road gradient), affecting noise generation, was analytically defined and represented in the model. Reviewing the existing traffic noise criteria in the world and TEM countries, the prediction model was then improved to establish TEMnoise standards taking into account environmental factors and was implemented for the required performances of the noise abatement measures applicable in every type of TEM. [Supported by Directorate of Turkish Highways within the TEM project coordinated by United Nations, Transport Division.]
77(1985); http://dx.doi.org/10.1121/1.2022318View Description Hide Description
It is well known that normal sleep, as measured by the EEG is not a uniform state but varies from shallow to deep sleep in a cyclical manner. The duration of the cycle is roughly 1.5 h. It has been suggested that disruption of these cycles can have unfavorable effects on a subject's performance during the following day [M. Herbert and R. T. Wilkinson, Proc. Mt. Congress on Noise as a Public Health Problem (1973)]. Twelve subjects slept in 60 dB of free‐flowing traffic noise on 12 alternate nights while the level during the other 12 nights was the ambient level of about 32 dB. If every waking or shift to a shallow sleep level is considered to be the beginning of a new cycle, then the average number of cycles per night during the noise night is about 6% greater than during the quiet nights. If only an extended period of shallow sleep is judged to be the beginning of a new cycle, then noise has no effect on the number of cycles per night.
- Session B. Physical Acoustics I: Solids
77(1985); http://dx.doi.org/10.1121/1.2022319View Description Hide Description
There has been a great deal of recent interest in using spectral analysis of backscatteredultrasonic signals to characterize material microstructure. As quantitative backscatter measurements can require signal averaging over several spatial orientations, a time consuming proposition, an alternative is needed. In this work the feasibility of using the spectral analysis of transmitted wideband signals was investigated. To precisely control grain size, samples were made by sintering glass beads of varying diameter. Porosity could be changed by altering the heat treatment of the samples. Results over the frequency range from 0.5–15 MHz are presented for specimens prepared with grain sizes ranging from 0.5–4 mm in diameter.
77(1985); http://dx.doi.org/10.1121/1.2022320View Description Hide Description
The ultrasonicelastic waves generated while an electric spark strikes a solid are investigated. Attention is given to the interaction with aluminum specimens and to cases where no apparent damage is observed. Several mechanisms are suggested as the source for the generated waves, and experiments investigating each of these mechanisms are described. It is found that the thermo‐elastic mechanism is of primary importance in the range of electric currents considered. As in the case of low energy laser‐generated ultrasound, the ablation mechanism becomes significant only at higher currents, when visible damage to the surface of the specimen is apparent. [Work supported in part by Materials Science Center at Cornell University.]
77(1985); http://dx.doi.org/10.1121/1.2022321View Description Hide Description
The quasicrystalline approximation (QCA) was first introduced by Lax to break the infinite heirarchy of equations that results in studies of the coherent field in discrete random media. It simply states that the conditional average of a field with the position of one scatterer held fixed is equal to the conditional average with two scatterers held fixed, i.e., 〈ψ〉 ij i = 〈ψ〉 i i . The QCA has met with great success for a range of concentrations from sparse to dense and for long and intermediate wavelengths. In this paper, the QCA is interpreted as a partial resummation of the multiple scattering series that includes only two body correlations and yields the same dispersion equation. Explicit improvements to the QCA are presented that still require only a knowledge of the two body correlation function.
77(1985); http://dx.doi.org/10.1121/1.2022322View Description Hide Description
The behavior of transversely isotropic elastic media is analyzed from both the kinematic (slowness surface) and dynamic (particle displacement) point of view. The relations for the slowness surfaces and wave front surfaces are derived in polar coordinates. Examination of the eigenvectors of the displacement equations of motion gives the relation for the polarization of the displacement vector associated with any plane wave. It is shown that the polarization of plane quasi‐P and quasi‐SVwaves depends strongly on the sign of a particular elastic modulus, call it A, whereas the shape of the slowness surface is independent of the sign of A. When A is positive, which is the usual case, the particle displacement vector rotates in the same sense as the slowness vector. When A is negative, which is the “anomalous” case, the sense of rotation of the particle displacement vector is opposite to that of the slowness vector. Thus there is a direction in the medium for which the displacement vector associated with the quasi‐P sheet of the slowness surface is perpendicular to the slowness vector and that associated with the quasi‐SV sheet is parallel to the slowness vector. For both sheets the angle between the slowness vector and the displacement assumes all angles between 0 and π/2. This case even includes media that are “nearly” kinematically isotropic, i.e., characterized by spherical wave fronts emanating from point sources.
77(1985); http://dx.doi.org/10.1121/1.2022370View Description Hide Description
Chalk squeal is a common phenomenon encountered in the classroom. The sound radiated from a chalk/blackboard system is possible because of two physical characteristics of the system. The first characteristic is that the frictional forces at the board and chalk interface are not constant when (stick‐slip phenomenon) steady, normal, and shear forces are exerted on the chalk. The second characteristic is that the resonances of the chalk are excited by the stick‐slip forces at the interface. A positive feedback system exists between the two characteristics and the vibrations are reinforced with the result that tonal squeal is generated. The resultant vibrations are called relaxational vibrations. Impedance measurement results are presented and compared to the radiated sound. The influence of the board characteristics are discussed. Methods of reducing chalk squeal are discussed. This work is important to the study of sound radiation from machinery operations, such as the honing of cylinders, which also exhibit relaxational oscillations. [Work supported by Department of Health and Human Services CDC/NIOSH Grant No. 1R43 OH01951‐01.]
77(1985); http://dx.doi.org/10.1121/1.2022371View Description Hide Description
The interaction between ultrasonicLamb waves and the region of rigid contact between two elastic layers is discussed. This problem is a model of two sheets welded in this region. The transmission of Lamb waves through such regions is estimated. The conversion of Lamb modes plays a major role. The effect of the temperature change in the welded region is also discussed. The effect of phase transformation in metal, metal melting, and solidification on wave transmission are described. Permanent address: Materials Engineering Department, Ben‐Gurion University of the Negev, P.O. Box 653, Beer‐Sheva, 84105 Israel.
77(1985); http://dx.doi.org/10.1121/1.2022372View Description Hide Description
When an ultrasonic wave propagates in a solid with a low concentration of voids the attenuation coefficient is proportional to the scattering cross section of each void multiplied by the number of voids [Gubernatis and Domany, Rev. Prog. QNDE 2A, 833 (1983)]. Exact calculation was carried out for the scattering cross section of elastic waves as a function of ka from spherical voids in several solids. A turning point between low and high ka values of the scattering cross section provides a turning point at ka = 1. This turning point depends only on the ratio of transverse to longitudinal velocity in the solids—can be used to calculate both the pore radius and their concentration. Experimental method was developed to measure attenuation coefficient as function of frequency using ultrasonic spectroscopy system. The theoretical model was successfully tested experimentally for several aluminum cast materials containing porosity up to 6% and with average radius for 10–150μ. [This work was supported by the Center of NDE operated by Ames Laboratory for the Air Force Wright Aeronautical Materials Laboratory.]
77(1985); http://dx.doi.org/10.1121/1.2022373View Description Hide Description
We discuss a new ultrasonic method for evaluation of interfaceproperties. The method is based on utilization of the ultrasonicinterface waves, for bonded semispaces and of Lamb waves for bonded layers. Using theoretical analysis we select experimental conditions in a manner such that the interface wave induces only shear stresses on the interface. This makes it possible to estimate the effective shear modulus of the interface. The effect of boundary conditions between layers on Lamb wave propagation and conversion is also considered. The transformation coefficients for Lamb waves conversion on the bonded and nonbonded regions between layers are derived and discussed.
77(1985); http://dx.doi.org/10.1121/1.2022374View Description Hide Description
It has already been reported by the author at a previous meeting [J. Acoust. Soc. Am. Suppl. 73, S95 (1982)] that certain types of transition layers can improve the transmission of acoustic waves from one medium to another. In this paper, conditions under which the transmissions of an acoustic wave is enhanced by the transition layer are presented. The case of a finite thickness elastic layer has been studied and it has been determined that at certain key frequencies, an optimum transition layer thickness exists which greatly improves the interaction between the two media.
77(1985); http://dx.doi.org/10.1121/1.2022375View Description Hide Description
When a plate is stiffened with a periodic array of ribs, the normal modes of the system are extended and structural vibrations may travel long distances with little scattering. If the rib array is made random, then structural vibrations become localized within a distance inversely related to the degree of randomness. This effect, analogous to a phenomenon in solid state physics, is referred to as Anderson localization. At the present time we are using nearfield acoustic holography to study the possibility of controllingsound radiation from ribbed plates through the effects of Anderson localization. Results from a one‐dimensional system will be reported. [Work supported by ONR and NASA.]
77(1985); http://dx.doi.org/10.1121/1.2022376View Description Hide Description
The problem of acoustic diffraction by nonrigid scatterers in water was treated both theoretically and experimentally. A theoretical model of diffraction by a matrix of square or rectangular blocks was developed. The Helmholtz integral equation was solved by making Kirchhoff‐type approximations that relate surface pressure to transmission and reflection coefficients calculated from the Brekhovskikh layered media model. Experimental measurements of pressure amplitude and phase difference were made on the shadow side of matrices of metal blocks. The blocks were insonified by sound waves of frequencies 2500 and 3500 Hz. An array of three hydrophones on the shadow side of a matrix sensed diffracted pressure amplitude and phase as a function of distance between the matrix and the hydrophones. Comparison of model predictions and experimental data shows good agreement. The agreement for small hydrophone‐matrix separations becomes better with increasing ka where 2a is the outside dimension of the matrix. [Work supported by NAVSEA, Code 55N and DTNSRDC Code 1933.]