The new Dyson Airblade dB hand dryer is said to create two sheets of high velocity unheated air that travel through 0.4mm scallop-shaped apertures.
According to Dyson, the scallop design increases the distance travelled by the two sheets of air before they collide.
An overhanging lip on the front aperture alters the angle of the air exiting the machine, further reducing the sound made when the sheets collide.
September 1935: Class A4 locomotive enters service
And your last sentence continues to this day!