Measuring loudness

The idea

Loudness of sound is commonly measured in decibels (dB); even a small increase in the dB level means a large increase in sound intensity.

Soft, normal, very loud

Rustling leaves are very soft. A normal talk is louder. A bursting firecracker is very loud. Scientists put numbers on these using a scale.

In which unit do you think loudness is commonly measured?

• Decibels (dB)
• Hertz (Hz)
• Metres (m)

Use the scale

Choose a sound and see where it lies on the decibel scale.

The decibel

Loudness is commonly measured in decibels, written dB. Rustling leaves are around a few dB, normal conversation is about 60 dB, and firecrackers can exceed 100 dB. A small rise in dB is a large rise in intensity.

Loudness of sound is commonly measured in decibels (dB). Even a small increase in the dB level means a large increase in sound intensity.

Notes

Loudness is commonly measured in decibels (dB). A small increase in dB means a large increase in intensity.

Check yourself

In which unit is loudness of sound commonly measured?

About how many decibels is a normal conversation?

Answer: 60 dB

Normal conversation is about 60 dB.

The sound level rises by a small amount in dB. What does this mean for the sound intensity?

Which of these sounds can exceed 100 dB?

• Hertz (Hz). The hertz is the unit of frequency. Loudness is commonly measured in decibels.
• Decibels (dB) — correct. Yes!
• Metres (m). The metre is the unit of wavelength. Loudness is commonly measured in decibels.
• A small increase in intensity. Even a small increase in the dB level means a large increase in sound intensity.
• No change in intensity. Even a small increase in the dB level means a large increase in sound intensity.
• A large increase in intensity — correct. Yes!
• Firecrackers — correct. Yes!
• Rustling leaves. Rustling leaves are very soft, around a few dB.
• Normal conversation. Normal conversation is about 60 dB.