A proposed experiment to evaluate environmental dependence of the measurement of noise from medium and heavy duty trucks

Holmer, Curtis I.; Kilmer, R

doi:10.6028/nbs.ir.76-1138

Cited by 2 publications

(5 citation statements)

References 7 publications

(12 reference statements)

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“…[1] * In applying such a regulation, it is necessary to be assured of a high degree of precision in the measurement procedure. Two areas of variability have been pointed out [2] which may affect the precision of test procedures of this type.…”

Section: Rationalementioning

confidence: 99%

“…Here a is the angle of incidlSce of the plane wave, measured from the horizontal, and 3 = pc/z (1)(2)(3) is the specific acoustic admittance ratio of the surface (pc is the specific impedance of air).…”

Section: Definitions and Assumptionsmentioning

confidence: 99%

“…The reflection coefficient has been written as i<f> r e (2)(3) From C^, the specific acoustic admittance ratio 8 is computed using 6 = 1-C 1+C (2)(3)(4) obtained from Eq. (1-2) for the case of normal incidence.…”

Section: Description Of Techniquementioning

confidence: 99%

“…If the source has a very strong pure tone, the measured level could be altered by many decibels as a result of the phase shift on reflection. For realistic spectra, errors of a few (2)(3) decibels are quite possible. Quantitative correction of such errors is not practical, since they would be highly sensitive to tone frequency and source-receiver geometry, and the slightest wind or temperature effects would alter the correction.…”

Section: Real Admittancementioning

confidence: 99%

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Techniques for the measurement of acoustic impedance of asphalt

Mansbach¹,

Holmer²

1978

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Five techniques were used for the measurement of the very high specific acoustic impedance of an asphalt surface.These techniques are: Impedance Tube, Pure-Tone Traverse, Pulse-Echo, Broad-Band Cross-Correlation, and Direct Accelerometer Measurement. These technqiues, as used in the present investigation, are described and evaluated in some detail, and the results of the measurements are presented.Of the five techniques, the broad-band crosscorrelation proved to be the most effective, and is readily capable of even further improvement.The value of the specific acoustic admittance ratio, pc/z, (averaged over frequencies) of the sealed asphalt surface obtained with this technique is .007.The effects of atmospheric wind and temperature gradients on ray propagation, and spherical wavefront corrections to planewave reflection, are derived theoretically.These refinements are necessary to realize the full potential of the broad-band measurement technique.Effects of the finite test surface impedance on source emission measurements are discussed.Variations in measured sound levels of the order of 1-2 dB due to differing impedances at different test site surfaces are considered likely, given the limited data on asphalt impedance presently available.1 ACKNOWLEDGMENTS

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Section: Rationalementioning

confidence: 99%

Section: Definitions and Assumptionsmentioning

confidence: 99%

Section: Description Of Techniquementioning

confidence: 99%

Section: Real Admittancementioning

confidence: 99%

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Techniques for the measurement of acoustic impedance of asphalt

Mansbach¹,

Holmer²

1978

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“…Although it may not be feasible to determine "correction factors" for environmental effects, it is fully expected that the data obtained from this experiment will reveal the magnitude of variations in the measurement and provide a broad enough information base. for study of the underlying physical mechanisms [31].…”

Section: Adequacy Versus Needsmentioning

confidence: 99%

The National Measurement System for acoustics

Pallett¹,

Cadoff²

1977

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This report was initially prepared during 1974 in response to a request from the Institute for Basic Standards office, and was intended to be, primarily, an internal, working document. Thus, the NBS role in the national measurement system for acoustics has probably been emphasized to a greater degree than what, in reality, actually exists. Also, because the field of acoustics is a dynamic, rapidly changing area, certain information contained in this report may rapidly become outdated.

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A proposed experiment to evaluate environmental dependence of the measurement of noise from medium and heavy duty trucks

Cited by 2 publications

References 7 publications

Techniques for the measurement of acoustic impedance of asphalt

Techniques for the measurement of acoustic impedance of asphalt

The National Measurement System for acoustics

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