No abstract

A survey of complaints about infrasound and low frequency noise has been carried out. 198 persons reported about their troubles in a questionnaire. Their verbal reports often describe a "deep and humming or rumbling sound, like coming from a distant idling engine of a truck or pump". Nearly all respondents report of a sensory perception of a sound. In general they report that they perceive the sound with their ears, but many mention also a perception of vibrations, either in their body or of external objects. The sound disturbs and irritates during most activities, and many consider its mere presence as a torment to them. Many of the respondents report on secondary effects, such as insomnia, headache and palpitation, which they associate with the sound mainly because it occurs at the same place. In a majority of the cases, only a single or few persons can hear the sound, but there are also examples, where it is claimed to be audible to everybody. Typically, measurements have shown that existing limits (and hearing thresholds) are not exceeded. The investigation leaves the key question: Are the troubles induced by an external sound or not, and if they are, which frequencies and levels are involved? The feasibility of a study of this is supported by the results.

No abstract

A survey of complaints about infrasound and low frequency noise has been carried out. 198 persons reported their troubles in a questionnaire. Their verbal reports often described the sound as deep and humming or rumbling, as if coming from the distant idling engine of a truck or pump. Nearly all respondent's reported a sensory perception of a sound. In general they reported that they perceived the sound with their ears, but many mention also the perception of vibration, either in their body or in external objects. The sound disturbs and irritates during most activities, and many consider its mere presence as a torment to them. Many of the respondents reported secondary effects, such as insomnia, headache and palpitation, which they associtated with the sound mainly because it occured at the same place as the sound. In a majority of the cases, only one or a few persons can hear the sound, but there are also examples, where it is claimed to be audible to everybody. Typically, measurements have shown that existing limits (and hearing thresholds) are not exceeded. The investigation leaves the key question: Are the troubles induced by an external sound or not, and if they are, which frequencies and levels are involved? The feasibility of a study of this is supported by the results.

Binaural equal-loudness level contours and the threshold of hearing have been measured on 25 otological normal-hearing subjects. In the frequency range from 50 Hz to 1 kHz the measurements were made in the free field for frontal sound incidence. From 20 to 100 Hz the experiments were made in a pressure field chamber with an inner volume for the test subjects of approximately 1 m3. The experiment is made with pure tones at each of the third octave frequencies in the frequency range. Loudness levels between 20 and 100 phon are measured. The data are going to be used for the standardization work in the Working Group ISO/TC43/WG1 for a revision of the international standard ISO 226.