A New Approach to Assess Low Frequency Noise in the Working Environment.

Abstract

To assess high-level low frequency noise in the working environment, adverse extra-aural effects caused by the noise should be taken into account. The human body vibration induced by low frequency noise, 'noise-induced vibration', was measured on the body surface and the equalacceleration level contours of the vibration were tentatively estimated. With these contours, we can predict the magnitude of noise-induced vibration at every measuring position on the body surface. This is helpful in relating the total dosage of low frequency noise with the physical symptoms caused by the noise. But some important points in the contours remain to be investigated and improved. When these points are dealt with, the equal-acceleration level contours will be useful for assessing high-level low frequency noise in the working environment from the standpoint of predicting the adverse extra-aural effects.

A Consideration of an Evaluation Index for High-Level Low-Frequency Noise by Taking into Account the Effect of Human Body Vibration

“…For practical use, it is preferable that a frequency-weighting characteristic corresponding to an evaluation index is available. In a previous study using lowfrequency pure tones as noise stimuli, the equal-acceleration level contour was considered to be a contour connecting the sound pressure levels at which equal VALs of noise-induced vibrations were induced, and roughly estimated the contour in the 25-to 50-Hz range [22]. Using the notation of the present study, the equalacceleration level contours estimated at the chest can be expressed approximately as SPL = -50 x log 10 (f) + VAL + 90, where f is the frequency [Hz] and SPL is the non-weighted sound pressure level [dB(SPL)] of a low-frequency noise stimulus.…”

“…Frequency-weighting characteristics corresponding to the HLLF indices Using the equal-acceleration level contours estimated at the chest[22], the HLLF1 index could be rewritten asHLLF1 = 0.045 x [SPL + C A (f)] + 0.062 x [SPL + 50 x log 10 (f) -90 + C k (f)] -5.0 = 0.107 x [SPL + 0.42 x C A (f) + 0.58 x C k (f) + 29 x log 10 (f)]-10.6 where C A (f) and C k (f) represent the correction functions for the A-and W kweighting characteristics as C A (f) and C k (f), respectively. By regarding the correction terms for the SPL in brackets as a frequency-weighting function, we temporarily defined the tentative HLLF1-weighting characteristic as C HLLF1 (f) = 0.42 x C A (f) + 0.58 x C k (f) + 29 x log 10 (f).…”

Multilevel multi-integration algorithm for acoustics

“…Infrasound can also be produced by devices used in daily life such as woofers, vehicle structures, and fans. Research has indicated that prolonged exposure to infrasound forms a serious health risk [65]. On the other side of the spectrum, ultrasound encompasses all sound with a frequency larger than the upper limit of the human hearing (20 KHz).…”