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Ionising radiation doesn’t just come from specially prepared samples to be used in equipment, ionising radiation is in nature as well. The core, mantle and crust of the earth contains quite a bit of radioactive material and a lot of building materials and other objects in our daily life are radioactive. Even outer space is filled with ionising radiation sent out there by ordinary things like our sun.
All that radiation combined is called the natural background radiation and it is in such low levels that it doesn’t pose a threat to your health. You could even say that this radiation is so normal, evolution and natural selection made sure that any lifeform that couldn’t cope with this amount of radiation never made it out of the primordial soup.
You cannot do much to reduce your exposure to natural background radiation, but great care is needed when handling radioactive materials. This is why radioactive materials have to be kept in special container labelled with the appropriate hazard symbol.
The source to the right even has a friendly instruction printed on the casing:
Drop and Run.
This container contains Cobalt-60 and that can still be found in modern hospitals to radiation tumours and sterilise equipment. After an incident in Thailand (the Sumat Prakan incident) at which the symbol wasn't recognised, a no warning sign was developed.
The unit used on the casing, the Curie, is not an official unit and is used less frequently nowadays,
Equipment
It is quite impossible to go ahead and count the amount of unstable atoms in a piece of radioactive material. First, how would you do that? They are tiny. Second, 1 gram of Carbon-12 is about 5,0·1022 atoms, you’d need more time than the current age of the universe.
With the right equipment, we can measure the amount of particles that are being sent out of the material. That piece of equipment is called a Geiger-Müller counter (or just Geiger counter) and by counting the amount of times it is hit by an ionising particle, you then can calculate the amount of “hits” per second. This is called the count rate.
The unit in which this counter measures is the Becquerel (Bq) and that is simply the amount of particles.
It seems exaterated, having a little sound each time a particle is received but is does serve a purpose. A lot of devices that detect a dangerous situation use light or sound to inform he user. With this, even a less then well-informed user will understand that he is in danger and hopefully, take the appropriate action (run away!).
The sound of a Geigercounter is well known, even if it’s just from TV but since radiation is so dangerous and invisible, it’s a good thing to know that sound.
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