Whistle Online: Referee Whistle Sound and Signals

Because a whistle is held. For a referee the length of the blast is the message: a short one and a long one mean different things. A recording has a single length, and a looped one is audible at the seam. Synthesis gives any length and sounds in the same millisecond; once the page has loaded it needs no network for that.

Quieter. A pealess referee whistle puts out around 115 dB, and no phone speaker will match that. The band does match, though: the signal is concentrated in 2–5 kHz, where the ear hears best and a phone speaker gives its most. In a small hall, on a court and at a pool that is enough; at a stadium, plug a laptop into a speaker and signal with a clicker.

It depends on the sport, which is why the labels here follow your choice. In football one short blast stops play and two long ones end the half. In volleyball a short blast authorises the serve. In a PE lesson two short usually mean stop and three mean line up. Pick the sport and the labels line up with it.

On a computer, yes: blasts are queued on the sound card clock, and while the tab is in the background the queue is filled more than a minute ahead, so timers slowed down by the browser do not break the tempo. On a phone, keep the screen on: while the program runs the page keeps it from going dark, and a locked phone may put the browser to sleep together with its sound. A held blast is released on purpose when the tab goes to the background, otherwise a phone in a pocket would whistle through the whole lesson.

Turn on the Clicker switch in the Clicker and keys section. A wireless clicker and most Bluetooth buttons send Page Down and Page Up to the computer or phone: the first gives a short blast, the second a long one. While the switch is off, those keys scroll the page as usual.

At arm length, no. But do not hold the phone to your ear and do not give the signal through headphones: it is deliberately dense in the band the ear is most sensitive to, and close up at full volume it is unpleasant. The slider on the page works on top of the system one, so turn it down here.