R-weighting provides better estimation for rat hearing sensitivity

Abstract

SummarySince sounds may induce physiological and behavioural changes in animals, it is necessary to assess and define the acoustic environment in laboratory animal facilities. Sound studies usually express sound levels as unweighted linear sound pressure levels. However, because a linear scale does not take account of hearing sensitivity-which may differ widely both between and within species at various frequencies-the results may be spurious. In this study a novel sound pressure level weighting for rats, R-weighting, was calculated according to a rat's hearing sensitivity. The sound level of a white noise signal was assessed using R-weighting, with H-weighting tailored for humans, A-weighting and linear sound pressure level combined with the response curves of two different loudspeakers. The sound signal resulted in different sound levels depending on the weighting and the type of loudspeaker. With a tweeter speaker reproducing sounds at high frequencies audible to a rat, R-and A-weightings gave similar results, but the H-weighted sound levels were lower. With a middle-range loudspeaker, unable to reproduce high frequencies, R-weighted sound showed the lowest sound levels. In conclusion, without a correct weighting system and proper equipment, the final sound level of an exposure stimulus can differ by several decibels from that intended. To achieve reliable and comparable results, standardization of sound experiments and assessment of the environment in animal facilities is a necessity. Hence, the use of appropriate species-specific sound pressure level weighting is essential. R-weighting for rats in sound studies is recommended.Keywords Auditory sensitivitYi hearing; physiologyi rati sound level; weightings All animals in animal facilities are exposed to environmental sounds. Various sounds have been shown to elicit physiological and behavioural changes in animals, which mean that the acoustic environment should also be controlled. The effects of sounds on hearing, different organs, growth, blood and the circulatory system have been reviewed by several groups (Pfaff 1974, Algers et a1. 1978, Peterson 1980, Gamble 1982. Moreover,

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