Berger E H, Killion M C
E-A-R Division, Cabot Corporation, Indianapolis, Indiana 46268-0898.
J Acoust Soc Am. 1989 Oct;86(4):1392-403. doi: 10.1121/1.398699.
The noise-excluding properties of a standard supra-aural audiometric earphone, a widely used circumaural-supra-aural combination, and an insert earphone sealed to the ear with a vinyl foam eartip were measured in a diffuse-field room complying with ANSI S12.6-1984. Data on attenuation were obtained monaurally with the nontest ear plugged and muffed. Results for the supra-aural earphones generally agreed well with previously reported measurements. A broadband masking noise was used to directly test the ANSI S3.1-1977 permissible background noise levels for measuring to audiometric zero using standard audiometric earphones. This "ANSI noise" raised the average thresholds of 15 normal-hearing test subjects by 3 to 5 dB at the octave frequencies from 500 to 4000 Hz. With a noise conforming to the less stringent OSHA-1983 regulation, average thresholds were elevated 9 to 17 dB. An "ENT office noise" with an overall sound level of 54 dBA raised average thresholds even further, by as much as 29 dB at 500 Hz. Use of the circumaural system in the office noise limited the threshold elevation to 11, 5, 2, and 0 dB at the four octave frequencies tested. With the fully ("deeply") inserted foam eartips, the threshold elevation in the simulated office noise was 2 dB or less at all test frequencies. Actual threshold elevations agreed closely with predictions based on a critical ratio calculation utilizing measured sound field noise levels and measured earphone attenuation values.
在符合ANSI S12.6 - 1984标准的扩散场房间中，测量了标准耳挂式听力计耳机、广泛使用的耳罩 - 耳挂组合以及使用乙烯基泡沫耳塞密封到耳朵的插入式耳机的隔音性能。在非测试耳堵塞并 muffed 的情况下，单耳获得衰减数据。耳挂式耳机的结果与先前报告的测量结果总体上非常吻合。使用宽带掩蔽噪声直接测试了ANSI S3.1 - 1977中使用标准听力计耳机测量听力零级时允许的背景噪声水平。这种“ANSI噪声”在500至4000 Hz的倍频程频率下，使15名正常听力测试对象的平均阈值提高了3至5 dB。对于符合不太严格的OSHA - 1983规定的噪声，平均阈值提高了9至17 dB。总体声级为54 dBA的“耳鼻喉科办公室噪声”甚至进一步提高了平均阈值，在500 Hz时高达29 dB。在办公室噪声中使用耳罩式系统，在测试的四个倍频程频率下，阈值升高限制在11、5、2和0 dB。使用完全（“深度”）插入的泡沫耳塞，在所有测试频率下，模拟办公室噪声中的阈值升高为2 dB或更低。实际阈值升高与基于利用测量的声场噪声水平和测量的耳机衰减值进行的临界比计算的预测非常接近。
