The latest Dihour hand dryer has been developed specifically with its sound quality in mind

The latest Dihour hand dryer has been developed specifically with its sound quality in mind.  This product is a high speed hand dryer comprised of two high velocity sheets of air which wipe the water from the user’s hands leaving them dry in 12 seconds. It has been found that the subjective perception of the noise generated by the hand dryer does not fully correlate with the measured sound power level. As such, the parameters driving the subjective sound quality were investigated.  To assess the sound quality of the hand dryer, a paired comparison test was carried out using binaural recordings of various hand dryer models. The psychoacoustic metrics of loudness and tonality were identified as key parameters and a pleasantness model was derived based on these results.  The high tonality observed in early prototypes of the hand dryer contributed to a low sound quality as identified by the pleasantness model. To further understand the influence of these tonal components, detection and annoyance thresholds of tonal noise embedded within a representative broadband noise signal were identified using a staircase method.  This work focussed on the reduction of tonal noises related to the rotational speed of the compressor.