Annoyance of low frequency noise

Low-frequency noise is usually defined as noise with dominant components below about 200 Hz. It has previously been shown that the A-weighted noise level underestimates the adverse effects such as annoyance and performance due to low frequency noise. Previous studies also suggest some properties of noise that determine, to which extent the low-frequency part is particularly annoying. One such property is the relative balance between low and high frequencies, sometimes referred to as the slope of the spectrum. A perceptual characteristic, which has been found to be particularly annoying, is the sensation of "rumble", a sensation that at least partly can be explained by the presence of level fluctuation in the low frequency range. In order to obtain a measure that better predicts the adverse effects of low frequency noise, the project attempts to evaluate and describe annoying sound properties of low-frequency noise more accurately than is possible using present assessment methods. The project will use psychometric procedures developed in a general project on annoyance (see project “Annoyance from Noise”). A factor that is of particular importance for experiments with low frequency noise is the exposure technique in the laboratory. Since low frequencies at higher sound pressure levels may not only affect the hearing but also give sensations in other parts of the body, mainly the chest and abdomen, an ear-only exposure (headphones) may therefore give another sensation than a full-body exposure (loudspeaker). To investigate this, a noise with significant low-frequency contents was therefore included in a general study on exposure techniques (see project “Recording and playback techniques for assessment of noise in the laboratory”). Supported by STVF/FTP.