Science · Physical Science
Measuring the Loudness of Sound
Reading comprehension passage and printable worksheet about how sound loudness is measured in decibels and what affects the intensity of sound — for grades 4–7.
Subject
Science
Grade Level
Grades 3–8
Resource Type
Lesson Plan
Format
Lesson + PDF
Reading Passage
Measuring the Loudness of Sound
Sound is a form of energy that travels as waves through the air and other materials. One of the most important properties of a sound wave is its loudness — how intense the sound is when it reaches our ears. Loudness depends on the amplitude of the sound wave, which is the height of the wave. A sound wave with a larger amplitude carries more energy and produces a louder sound.
Scientists measure the loudness of sound using a unit called the decibel (dB). The decibel scale is logarithmic, which means that each increase of 10 decibels represents a tenfold increase in sound intensity. A whisper is about 30 decibels. Normal conversation is around 60 decibels. A lawnmower operates at about 90 decibels. A rock concert can reach 110 decibels or higher.
The human ear can detect a wide range of sound intensities — from the faintest whisper to the roar of a jet engine. However, very loud sounds can damage the delicate hair cells inside the inner ear that detect sound waves. Sounds above 85 decibels can cause hearing damage with prolonged exposure. Sounds above 140 decibels — such as a gunshot or explosion — can cause immediate and permanent hearing loss.
The loudness of a sound decreases as you move farther from the source. This happens because the same amount of sound energy spreads over a larger area as the wave travels outward. Standing close to a speaker at a concert, the music may be painfully loud, but from far away, the same speaker sounds much quieter. This relationship between distance and loudness follows a mathematical pattern — doubling the distance reduces the sound intensity to about one quarter of its original value.
Sound engineers, audiologists, and hearing safety professionals all use decibel measurements in their work. Construction workers and factory workers who are regularly exposed to loud machinery are required to wear hearing protection when noise levels exceed safe limits. Noise-canceling headphones and earplugs work by reducing the amplitude of incoming sound waves before they reach the eardrum. Understanding how loudness is measured helps us protect our hearing and create safer environments.
Printable Worksheet
Printable PDF · 4 pages
Measuring the Loudness of Sound Reading Comprehension Worksheet
Printable worksheet includes the reading passage and comprehension questions about decibels, amplitude, sound intensity, and hearing safety. Includes answer key.
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