ANSI ASA S1.25-1991 American National Standard Specification for Personal Noise Dosimeters.pdf
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1、5HDIILUPHGE$16,-XO5HDIILUPHGE$16,0DUFK5HDIILUPHGE$16,0DUFK5HDIILUPHGE$16,0DUFKAMERICAN NATIONAL STANDARDS ON ACOUSTICS The Acoustical Society of America provides the Secretariat for Accredited Standards Committees S 1 on Acoustics, 52 on Mechanical Shock and Vibration, 53 on Bio acoustics, and S 12
2、on Noise. These committees have wide representation from the technical community (manufacturers, consumers, and general-interest representa tives). The standards are published by the Acoustical Society of America through the American Institute of Physics as American National Standards after approval
3、 by their respective standards committees and the American National Standards Institute. These standards are developed and published as a public service to provide stan dards useful to the public, industry, and consumers, and to Federal, State, and local governments. This standard was approved by th
4、e American National Standards Institute as ANSI S1.25-1991 on 24 October 1991. An American National Standard implies a consensus of those substantially concerned with its scope and provisions. An American National Standard is intended as a guide to aid the manufacturer, the umwmer, and the general p
5、ublic. The existence of an American National Standard does not in any respect preclude anyone, whether he has approved the standard or not, from manufacturing, market ing, purchasing, or using products, processes, or procedures not conforming to the standard. Ameri can National Standards are subject
6、 to periodic review and users are cautioned to obtain the latest editions. Cwtion Nottf:e: An American National Standard may be revised or withdrawn at any lime. The proce dure of the American National Standards Institute require that action be taken to reaffirm, revise, or withdraw this standard no
7、 later than five years from the dare of publication. The American National Standards Institute, Inc. (ANSI) is the national coordinator of voluntary standards development and the clearing house in the U.S. for information on national and international standards. The Acoustical Society of America (AS
8、A) is an organization of scientists and engineers formed in 1929 to increase and diffuse the knowledge of acoustics and to promote its practical applications. Published by the Acoustical Society of America through the American Institute of Physics 1992 by Acoustical Society of America. This standard
9、 may not be reproduced in whole or in part in any form for sale, promotion, or any commercial purpose, or any purpose not falling within the fair-use provisions of the Copyright Act of 1976, without prior written permission of the publisher. For permission, address the Standards Secretariat of the A
10、coustical Society of America. FOREWORD comfort. At the time this standard was submitted to Accredited Standards Committee S 1, Acoustics, for final approval, the membership was as follows: G. S. K. VVong, Cha R. L. McKinley, Vice-Chairman A. Brenig, Secretary Acoustical Society of America T. F. W. E
11、mbleton, G. S. K. Wong !A/t) Air-Conditioning and Refrigeration Institute S. Wang, ). Clukey !Ait) American Industrial Hygiene Association C. D. Bohl AT the criterion level is 90 dB, the threshold level is 80 dB and the exchange rate is 5 dB. The options for class designation are: Frequency Weightin
12、g Time Constant Criterion Level Threshold Level Exchange Rate A orC F (FAST); S (SLOW) 90, 85, 84, 80, V (Variable) 90, 80, V (Variable) 5, 4, 3 NOTE: For dosimeters with variable criterion and threshold lev els, the selected levels shall be specified in order to obtain a valid reading. 4. GENERAL C
13、HARACTERISTICS 4.1 General A noise dosimeter is generally a combination of a microphone, an amplifier with specified frequency weighting, a squaring device, an exponential averaging device with a specified time constant, a holding upper limit indicator, an exponent circuit with a specified ex-ANSI 5
14、1.25-1992 3 AMPLIFIER AND SQUARING MICROPHONE : FREQUENCY DEVICE WEIGHTING EXPONENTIAL EXPONENT THRESHOLD AVERAGING DEVICE CIRCUIT CIRCUIT HOLDING UPPER ILIMIT INDICATOR INTEGRATOR ! 1 INDICATOR j FIG. 1. Block diagram of functional elements of a noise dosimeter. ponent, a threshold circuit, a devic
15、e that integrates with respect to time, and an indicator. The actual in strument need not be separable into such individual functional elements since the primary basis of accept ability of the instrument is the overall performance. For convenience of description of the required charac teristics of t
16、he device, however, the instrument is treat ed as if it were a cascade of separable individual ele ments. (See Fig. 1.) 4.2 Relative Frequency Response The frequency characteristics of the overall instru ment are specified in Table 1. The relative response level is given at discrete preferred freque
17、ncies, but the response must be that corresponding to a smooth curve at the specified frequencies. The tolerances are identical to those for a Type 2 sound-level meter (ANSI S 1.4-1983). The specified tolerances are abso lute tolerances at the criterion level and at the refer ence ambient conditions
18、 specified in Sec. 7.1. Above 10 kHz, the roJl-off rate must not be Jess than 6 dB/oc tave. 4.3 Exponential Averaging The time constant of the exponential averaging de vice connected to the output of the squaring device is nominaJly 1 s, corresponding to the SLOW response of a standard sound level m
19、eter, or 0.125 s, correspond ing to the FAST response. NOTE: For dosimeters based on the 3 dB exchange rate, the ex ponential averaging device is optional. 4.4 Threshold The threshold circuit shall be placed after the expo nential averaging device in order that the integrator will properly integrate
20、 over sensed sound levels that exceed the threshold. 4.5 Integration The integrator integrates a power function of the mean square signal over time. This function is deter mined by the exponent circuit (see the block dia gram). The exponent depends on the exchange rate, being 0.6 for the 5 dB rate,
21、0. 75 for the 4 dB rate, and 1.0 for the 3 dB rate. The integrated output over time of the exponential circuit as modified by the threshold circuit is proportional to the percentage criterion expo sure. 4.6 Indicator The indicator may be built into or separate from the dosimeter. The number displaye
22、d shall be a percen tage. The resolution of the display shall be sufficient to express this percentage rounded to the nearest integer. 4 AMERICAN NATIONAL STANDARD TABLE l. Random incidence relative response level as a function of frequency for A- and C-weighting. (Type 2 Tolerances. ANSI Sl.4-1983)
23、. Nominal Exact A- C-Frequency Frequency Weighting Weighting Hz in Hz dB dB 20 25 31.5 40 50 63 80 100 125 160 200 250 315 400 500 630 800 1000 1250 1600 2000 2500 3150 4000 5000 6300 8000 10000 19.95 25.12 31.62 39.81 50.12 63.10 79.43 100.0 125.9 158.5 199.5 251.2 316.2 398.1 501.2 631.0 794.3 100
24、0 1259 1585 1995 2512 3162 3981 5012 6310 7943 10000 -50.5 -44.7 -39.4 -34.6 -30.2 -26.2 -22.5 -19.1 -16.1 - 13.4 - 10.9 -8.6 -6.6 -4.8 -32 - 1.9 -0.8 0 + 0.6 + 1.0 +1.2 +1.3 + 1.2 + 1.0 + 0.5 -0.1 -1.1 -2.5 -6.2 -4.4 -3.0 -2.0 -1.3 -0.8 -0.5 -0.3 -0.2 -0.1 0 0 0 0 0 0 0 0 0 -0.1 -0.2 -0.3 -0.5 -0.8
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