In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 12, No. 3_Supplement ( 1941-01-01), p. 463-463
Abstract:
Fifteen years ago saw the introduction of refinements in aircraft engine test equipment coincidental with growing production. It became necessary to build specially constructed houses for engine testing. As requirements of government and private specifications made continuous testing over periods of several days obligatory, incidental noise ranging up to one hundred forty decibels at the source became a growing nuisance in congested areas. Installation of sound absorbing materials presented real and unique problems because of the limitation inherent in the function of the building. Uninterrupted intake and exhaust airflows were necessary and passages had to be left open to the elements. Air velocities over one hundred miles an hour were involved. In addition, rigid fireproof requirements and maintainability were complicating factors. After early false starts with various absorbent media, porous and sound absorptive stone was found to be a practical material for the purpose. Arrangement of material has been approached in several ways, always with the requirement of uninterrupted airflow in mind. Honeycomb arrangement was first used, then ribbon walls of flat stone and later of beveled and perforated stone, as well as variations in the arrangement of the passages themselves, some being horizontal and some vertical. In the period of the last few years the aircraft engine manufacturers and the large users of engines such as the U. S. Army and Navy and the transport companies have become more conscious of the noise problem, partly due to complaints of nearby municipalities. The number of installations has grown and many noise readings have become available indicating the efficiency of various materials and arrangements of those materials. In many cases noise levels have been recorded in the test chamber itself, on top of the exhaust and intake passages, at various levels in these passages, as well as at varying distances from the test buildings and in varying weather conditions. Because of the variables such as engine horse power, propeller diameter, propeller tip speed and others, the results of comparative tests are indicatory rather than conclusive.
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
1941
detail.hit.zdb_id:
1461063-2
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