THE ACOUSTIC ENVIRONMENT OF THE DOMESTIC PIG

Measures have been introduced to reduce the health risk and nuisance o f agricultural noise to humans. However, humans are not the only anima ls that can be affected by sound. The sounds to which farm animals are exposed are not controlled and furthermore are relatively unknown. Th is study was carried out to determine the sound experienced by pigs th roughout their production. Recordings of noise were made at six farms, on five transporters and at four abattoirs. From these recordings, in formation extracted included averages and ranges of sound pressure lev els, ranges of frequencies and peak frequencies and sources of the noi se components. The average sound pressure level measured in mechanical ly ventilated pig buildings was 73 dB: naturally ventilated buildings were on average 10 dB quieter, but did tend to have a greater variatio n in intensity as indicated by the range between L-10 and L-90 values (the sound level exceeded for 10 and 90% of the measurement period, re spectively). The frequency content of the sound present on farms range d from 20 to 6300 Hz. Peaks in frequency, probably caused by fans, wer e identified in the mechanically ventilated buildings but not in the n aturally ventilated buildings. A diurnal variation in overall sound pr essure level was found in naturally ventilated buildings but not in me chanically ventilated ones. The average sound pressure level measured during transport was 91 dB (Lin). Only a small variation between diffe rent types of transporter was found. Peaks in frequency were identifie d, but their source was not investigated. No sound was measured at fre quencies above 16 kHz. The sound pressure level in abattoir lairages w as between 76 and 86 dB (Lin), though the pre-stun pens were louder, 8 9 to 97 dB (Lin). Pig vocalizations and moving machinery were signific ant sources of sound in all the areas surveyed. The sound levels and t ypes of sound that occur during transport and at the abattoir are like ly to be aversive to pigs and therefore should be regulated to improve pig welfare. (C) 1998 Silsoe Research Institute.