On December 30, 1975, the United States government issued a regulation which set limits on the amount of noise emitted from portable air compressors. This regulation also specified the noise test procedure to determine the maximum sound pressure level of compressors. On April 5, 1978, the Commission of the European Communities (CEC) submitted a proposed directive to the Council of the European Communities, that also would set limits on the noise emitted by portable air compressors within the European Economic Community (EEC). The proposed directive also specified the test procedure to determine the sound power emitted from a compressor. It became evident that both U.S. and European manufacturers may need to perform two separate noise tests on their compressors if they intend to meet both existing U.S. and the proposed EEC noise standards. At the request of industry, U.S. government representatives entered into discussions with representatives of the CEC in November 1975. These discussions led to an agreement between the CEC and the U.S. EPA to jointly conduct comparative noise tests of various size compressors to assess the potential for alignment of the existing U.S. and the proposed CEC test procedures. The test results presented in this report are the end product of those bilateral discussions and technical cooperation between the CEC and the EPA.