定价： 475元 / 折扣价： 404 元 加购物车

定价： 819元 / 折扣价： 697 元 加购物车

定价： 605元 / 折扣价： 515 元

定价： 156元 / 折扣价： 133 元 加购物车

定价： 156元 / 折扣价： 133 元 加购物车

定价： 481元 / 折扣价： 409 元 加购物车

定价： 260元 / 折扣价： 221 元 加购物车

定价： 0元 / 折扣价： 0 元 加购物车

定价： 156元 / 折扣价： 133 元 加购物车

定价： 156元 / 折扣价： 133 元 加购物车

定价： 0元 / 折扣价： 0 元 加购物车

定价： 0元 / 折扣价： 0 元 加购物车

5.1 Several ASTM test methods to evaluate the sound-insulating properties of building elements require the measurement of room sound absorption as part of the procedure. The room sound absorption in these standards appears in an equation in the form 10 log (x/A), where x is a quantity with the same units as A, m2. Room sound absorption is calculated from the decay rate using Eq 1.5.2 The requirements of this standard have been chosen so the uncertainty associated with the measurement of room sound absorption will be acceptably small so long as the logarithm of the absorption is being used in calculations.5.3 Other test methods should specify explicitly that they make use of this test method.5.4 Where measurement requirements in the parent standard differ from those given here, the requirements in the parent standard shall be satisfied.5.5 This test method shall not be used when room sound absorption or decay rate is to be used directly to satisfy some criterion, for example in a room that must not be overly reverberant so speech will be intelligible.NOTE 1: The uncertainty of the room sound absorption obtained will usually be too high and additional measurements are necessary.5.6 Any companion standard may specify the use of the procedures in this method for determining whether the decay rates in a room are slow enough to satisfy the requirements of the companion standard. The measured decay rates shall still be used only to calculate the logarithm of the room absorption.1.1 This test method covers the measurement of sound decay rate in rooms and the calculation of the sound absorption of the room and its contents. The sound absorption so calculated may be used in calculations in sound insulation test methods.1.2 The method shall be used only in conjunction with other test methods where the logarithm of the sound absorption is used in formulas. It is not sufficiently precise for use in situations where room sound absorption is to be used without taking logarithms.1.3 For laboratory measurements of the sound absorption of materials and objects, Test Method C423 should be used.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 515元 / 折扣价： 438 元 加购物车

This specification covers cast sound-signalling bells, together with bulkhead mounting plates for the smaller bells, for use on ships, boats, and other marine craft, for compliance with the rules in the convention on the International Regulations for Preventing Collisions at Sea. Bell bodies, clappers, and other cast fittings and parts shall be copper alloy. Fittings such as bolts, nuts, washers, pins, and supporting lugs shall be of copper alloy compatible with the bell castings. Bells shall have full, clear, round, and farreaching tones. The sound pressure level shall not be less than 110 dB at a distance of 1 m from it. Acoustic tests shall be conducted only for the 200 mm heavy and larger bells to check the requirements prescribed.1.1 This specification covers cast sound-signalling bells, together with bulkhead mounting plates for the smaller bells, for use on ships, boats, and other marine craft, for compliance with the rules in the convention on the International Regulations for Preventing Collisions at Sea (commonly called Colregs).2 See Appendix X1.1.2 Bells and bulkhead mounting plate shall be sized as indicated in Section 4 (see Appendix X2).1.3 For consistency with International Regulations, all measurements are in SI units.1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车

This specification covers gongs for use on ships of certain length, as required by International Regulations. The gong cylinder, brackets, clapper rod, "U" bracket, washers, and clapper support pin shall be made of stainless steel. The clapper mass shall be made of cast alloy steel. In addition, the support bolt, nut, flat washer, and cotter pins shall be made of stainless steel compatible with the other materials. The general arrangement of the assembled gong, as well as details of the gong cylinder, brackets, clapper, and miscellaneous fittings are presented. The sound characteristics of these gongs shall be determined by an acoustic test. These gongs shall be free from cracks, burrs, sharp cutting edges, and other defects affecting their life, appearance, and serviceability.1.1 This specification covers gongs for use on ships 100 m or more in length, as required by International Regulations (see Appendix X1).1.2 For consistency with International Regulations, all measurements are in SI units.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

定价： 590元 / 折扣价： 502 元 加购物车