Decibel facts for kids

A decibel (or dB) is a special unit used to measure how strong a sound or signal is. It helps us compare how loud one sound is compared to another. Think of it like a scale for loudness!

The decibel unit is based on something called a "bel." One bel means a sound is 10 times stronger. A decibel is simply one-tenth of a bel. So, if a sound gets 3 dB louder, it means its power has roughly doubled. Decibels are super useful in things like telecommunication, which is how we send messages over long distances. They also help measure electric audio signals, like in your headphones. For example, "dBm" is a decibel unit that compares a signal's power to one milliwatt.

The quietest sound most people can hear is often called 0 dB. This is known as the Absolute threshold of hearing. But what someone can hear can be different for everyone.

How Decibels Started

The "bel" unit, which decibels come from, was named after Alexander Graham Bell. He's famous for inventing the telephone! The "bel" was a bit too big for everyday use. So, people started using the "decibel" instead, which is one-tenth of a bel. Before bels and decibels, there was a similar unit called the Transmission Unit (TU).

Sound Levels and Protecting Your Ears

Decibels are often used to describe how loud a sound is. This is usually compared to the quietest sound a human can hear. The decibel is not an official SI unit, but it's used all over the world.

Here's a table showing how loud different sounds can be:

It's really important to protect your ears from loud sounds. Too much noise can damage your hearing forever. This next table shows how long you can safely be around certain noise levels without ear protection:

Images for kids

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  Examples of sound levels in decibels from various sound sources and activities, taken from the "How loud is too loud" screen of the NIOSH Sound Level Meter app

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  A diagram showing how dBu (a measure of voltage) relates to dBm (a measure of power)

See also

In Spanish: Decibelio para niños