Longer lasting sounds, for example continuous fan noise, can also affect pigs. Behaviour of piglets and sows during suckling in relation to sound levels were investigated by Algers and Jensen (1985). Sows were exposed to a relatively silent background noise of 59 dB or exposed to fan noise at a level of 85 dB. In the noise-exposed environment, the piglets failed to respond to the gruntings of the sow, which led to a disrupted pattern. Significantly decreased massaging of the udder and hence reduced milk production were recorded. Authors concluded that the noise-exposed piglets gained less milk than the ones in the silent environment. In the study of Algers (1984) with sudden noise exposure 10-day-old pigs an immediate attention and orientation reaction for about 10 s was noted. The 6-week-old pigs were immediately activated and started to orientate themselves towards the sound source. An intensive searching behaviour by all pigs started and continued for the whole 10 min period. Attention and waving of the ears were recorded initially in all sows (Algers, 1984). When suckling piglets were subjected to continuous loud noise, they were to a lesser extent attracted to the front teats and more frequently used the teats at the rear part of the udder (Algers and Jensen, 1991).