Standardization of equal -loudness level characteristics

在一个大的消声室中进行了听力实验，以获得等响水平轮廓。实验中测量了20、40和70 phon纯音的等响度等值线和自由场纯音听阈。通过实验得到以下结果。(1)在低于1 kHz的频率范围内，所有级别的等响水平等值线显示出与现行国际标准ISO 226的差异超过10 dB。这就意味着现行的标准需要全面修订. (2)所测得的听阈数据提交给国际标准化组织TC43。已决定出版新的国际标准ISO 226第1部分以及其他数据和来自德国和丹麦的其他数据。我们对这一标准化做出了巨大的贡献，因为只有我们的团队才能提供覆盖整个可听频率范围的数据。(3)我们发现，在1 kHz和2 kHz之间存在一个约2 dB的小峰值，用于等响轮廓和听力阈值。将该峰值与各个头部传递函数（从声源到收听者的外耳的声学路径的传递函数）进行比较，我们发现该峰值可以通过头部传递函数中的相应下降来解释。这说明头部传递函数是决定个体等响曲线和听阈的重要因素。

Hearing experiments to derive equal-loudness level contours were carried out in a large anechoic room. In the experiments, the equal-loudness level contours of pure tones at 20 phon, 40 phon and 70 phon as well as the threshold of hearing of pure tones in a free field were measured. We get the following results with the experiments.(1) The equal-loudness level contours at all the levels examined show discrepancy from the present international standard, ISO 226, by more than 10 dB in lower frequency range than 1 kHz. This means that the -present standard should be totally revised.(2) All the data of the threshold of hearing obtained were presented to TC43 of TSO (International Standardization Organization). It is decided that a new international standard ISO 226 Part 1 is to be published with other data and other data from Germany and Denmark. We contribute this standardization remarkably because only our group could present such data that covered all over the audible frequency range.(3) We found that a small peak of around 2 dB exists between 1 kHz and 2 kHz for both the equal-loudness contours and the threshold of hearing. Comparing this peak with individual head transfer functions (transfer function of a acoustic path from a sound source to the listener's external ear), we found that the peak can be explained by a corresponding dip in the head transfer functions. This shows that the head transfer functions is an important factor to determine individual equal-loudness contours and threshold of hearing.