The Acoustic Environment of the Domestic Pig

Measures have been introduced to reduce the health risk and nuisance of agricultural noise to humans. However, humans are not the only animals that can be affected by sound. The sounds to which farm animals are exposed are not controlled and furthermore are relatively unknown. This study was carried out to determine the sound experienced by pigs throughout their production. Recordings of noise were made at six farms, on five transporters and at four abattoirs. From these recordings, information extracted included averages and ranges of sound pressure levels, ranges of frequencies and peak frequencies and sources of the noise components. The average sound pressure level measured in mechanically ventilated pig buildings was 73 dB: naturally ventilated buildings were on average 10 dB quieter, but did tend to have a greater variation in intensity as indicated by the range betweenL10andL90values (the sound level exceeded for 10 and 90% of the measurement period, respectively). The frequency content of the sound present on farms ranged from 20 to 6300 Hz. Peaks in frequency, probably caused by fans, were identified in the mechanically ventilated buildings but not in the naturally ventilated buildings. A diurnal variation in overall sound pressure level was found in naturally ventilated buildings but not in mechanically ventilated ones. The average sound pressure level measured during transport was 91 dB (Lin). Only a small variation between different types of transporter was found. Peaks in frequency were identified, but their source was not investigated. No sound was measured at frequencies above 16 kHz. The sound pressure level in abattoir lairages was between 76 and 86 dB (Lin), though the pre-stun pens were louder, 89 to 97 dB (Lin). Pig vocalizations and moving machinery were significant sources of sound in all the areas surveyed. The sound levels and types of sound that occur during transport and at the abattoir are likely to be aversive to pigs and therefore should be regulated to improve pig welfare.