Hearing aids work well when there is little or no background noise and the person speaking is close to the microphone of the hearing aid (no more than a metre away). In the classroom situation, the deaf child is rarely this close to the teacher and classroom conditions are frequently noisy and reverberant. Background noise is amplified by the hearing aid as well as the teacher's voice. If the hearing aid is turned up to hear the teacher when she moves away, the background noise will also be amplified more by the hearing aid. The further away the teacher moves, the lower the level of her voice reaching the child's ear and the more intrusive the background noise. Alternative forms of amplification have been produced in an attempt to overcome these problems.