In 2000, a group of fifth graders in Centerville, Ohio took on a research question:
“Are there times or activities in our school when the noise level becomes dangerous to people’s hearing?” They discovered a number of places where sound levels were not safe and their article was published in Hearing Rehabilitation Quarterly.
I love the idea behind this. It’s an activity to learn how sound works, how to measure sound, and take those results and possibly make changes at your school. The great thing about this activity is anyone could recreate it and get their own results. It would work for a science class or a science fair project.
The experiment
- Learn about how sound works, how sound is measured (in decibels), and what level decibels can damage hearing.
- Identify what noises in school seem too loud
- Divide the main question into smaller tests to perform such as, “Which grade is the loudest (makes the most noise) at lunch? Did the noise reach a danger level?”
- Buy and learn to use an SPL meter (sound pressure level – to measure decibels)
- Set up the sound meter in different locations and take readings
Some areas they chose to test were the cafeteria, hallway, school bell (in the bathroom and hallway), gym class, and construction. Some other ideas to test might be music classes (band or orchestra – especially drums), rallies or special events at the school.
What SPL meter do I need?
SPL meters vary greatly in price but for this type of experiment all you need is a simple meter with a digital readout that reads dBA (the most common measurement “weighting” for decibels). The BAFX basic meter fits that and it’s under $20. More expensive models will get you better accuracy and more features but none of this is necessary at the non-professional level.
There’s a lot of SPL meter apps for mobile devices but research has shown some apps are highly inaccurate. The four apps they found to be most accurate during testing were SoundMeter, SPLnFFT, SPL Pro and NoiSee. The last company also created the NIOSH app (which is free).
When using an SPL meter app, the results are highly accurate (with 1 dB of a measurement mic) with an external calibrated microphone. Two mics that were tested and found to be very accurate were:
MicW i436 Calibrated Measurement Type 2 External Mini Microphone for iPad, iPhone, and iPod Touch (over $100)
How to use an SPL meter
Using a meter is very easy: Point the mic to the sound source. When you’re trying to test if a sound is too loud for a person, the best place to put the microphone is where someone’s ear would be. For example, if an SPL meter is placed two inches from a school bell (mounted high on a wall), it’s probably going to give a reading that’s above the safe level (and might even cause some temporary ear ringing). But, that’s not where anyone’s ears are going to be normally. If you take a reading from 4 feet above the ground, the reading might be a lot lower.
How to modify the experiment
- Toys. Can you find toys that are too loud? (Similar to Sight and Hearing’s yearly toy testing)
- Television and music systems. How loud is unsafe? Is it softer or quieter than you normally listen?
If you do this experiment, let us know the results!
I’d love to hear what you discover and what changes you try to make. Here’s the report from the students at Ida Weller Elementary School and their original experiment:
Stop the Noise: An Investigation of Sound Levels in Elementary School
Resources
Sound Is Fun: What sounds are too loud for children?
DKFindout: Sound
National Geographic Kids YouTube Playlist: The Science of Sound
How Does Sound Travel? Lesson for Kids
How Decibel Sound Level Meters Work