. First, 20 normal hearing consenting adult volunteers rated their audibility of the anaesthesia alarm using a 10-point numerical scale (0 = not audible to 10 = maximum audibility). Second, a sound level meter was used to measure the intensity of acoustic noise (A-weighted scale) under the above-mentioned conditions. Data, expressed as median [interquartile range], were analysed using the Wilcoxon test with P less than 0.05 considered as significant.