How do "referees" whistles make such a loud noise ?

Question

Hi Folks,

I have one in front of me on the desk. The standard chrome plated thing made by "lion", No.1041 for what it is worth.

I use it to scare stupid people who 'phone me trying to sell shares, or telling me I have won something.

I tried it on a freind, who reported it was just the right volume & frequency to be most alarming down a 'pnone line.

I recommend this tactic, but despite analysis, I can't work out how the rapidly revolving pea in the drum bit, passing the hole at a fair rate, produces such an an ear-ringing sound.

Any whistle experts ?

Bob

Answer 1

by blowing in to them  

Answer 2

The frequency is caused by the rotating "pea" in the drum but the volume is caused by the vibrations of an assortment of parts.

First the drum itself is thin metal which resonates at the frequency of the rotating pea - this thin metal acts as an amplifier of the vibrations. There is also air hitting the edge of the slot - this edge is thin metal which readily resonates and the vibrations are passed onto the thin metal drum. The air inside the drum also acts as a source of sound which then is projected out of the slot. Some of the vibrations also pass into the whistlers skull which also acts as a source of sound.

Answer 3

the ball actually stops the sound. the sound is created as the air flows through the whistle unobstructed. when the change of pressure causes the ball to be sucked onto the path of least ristance it blocks the airway, thus muting the sound. this happens over and over several times per second as thee pressures are equalized. it is not the loud noise produced that is really annoying, it is the constant up and down of the voume and pitch that is annoing.