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Laboratory Evaluation of Annoyance of Low Frequency Noise SummaryThe present report documents a project that was carried out in cooperation between The Department of Acoustic Technology, Technical University of Denmark and the Danish Environmental Protection Agency in year 2000. The purpose of the project was to investigate the subjective annoyance due to a number of low frequency noise examples. The main part of the project consisted of a series of listening tests, where a group of test persons listened to different examples of low frequency noise and gave their evaluation of the loudness of the noises and the annoyance of the noises. The main group of test persons (reference group) was eighteen young persons with normal hearing. The test persons evaluated eight different noise examples, where one example was road traffic noise and the other examples were realistic samples of environmental low frequency noise. The noise examples included both stationary noise with and without tones, intermittent noise (from a passing ferry), music, and impulsive low frequency noise from a punch press. The noises were presented in an IEC listening room at three different LAeq levels between 20 and 35 dB, and each presentation was repeated once in a random order. The subjective assessments made by the test persons were compared to objective results from a number of recent methods for assessment of low frequency noise. A total of seven different assessment methods were used. It was found that the Danish assessment method, published in Information No. 9/1997 from the Danish Environmental Protection Agency, "Low frequency noise, infrasound and vibration in the environment" gave the best relation to the subjective assessments made by the test persons. There was no obvious indication in the present results of how to further improve the Danish method. Apparently one important property of this method is that it includes a 5 dB penalty in case of impulsive noise. In addition to the main investigation with 18 young normal hearing test persons, listening tests were also made with a small group of four test persons, the special group. The special group consisted of four persons that had reported annoyance due to low frequency noise in their homes. It was found that the special group assessed the noise examples in a different way than the reference group. Generally the annoyance was much higher, especially the annoyance at night. It was also found that the two groups evaluated the noise samples differently. It was not the same types of noise that the two groups found most and least annoying. Due to the limited number of persons in the special group, no explanations of these differences can be indicated within the frame of the present investigation.
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