Last week the Nasdaq Nordic exchange was put out of order after a fire alarm in a Swedish data centre caused a fire suppression system to trigger. The system made such a loud noise that it shut down servers for the Nasdaq. The whistling sound may have damaged "the alignment of disk drives’ read-write heads to the data tracks," according to Quartz. LONDON — Stock market trading in seven European countries was knocked out for several hours last week with an unusual cause of the disruption — a loud whistling noise. According to reports, trading on the Nasdaq Nordic platform was delayed for hours last Wednesday after a fire alarm was accidentally triggered at a data centre in Väsby, Sweden, a town near Stockholm.