In 2000, a group of fifth graders at Ida Weller Elementary School (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 results were published in Hearing Rehabilitation Quarterly.
In 2019, 9-year-old Nora Keegan did a science fair project comparing the loudness of hand dryers in over 40 public restrooms. Nora found that many hand dryers were not a safe levels for kids, whose ears were closer to the dryer due to height and shorter arms than adults. Nora’s findings (along with and another science fair project she did a few years later) brought worldwide awareness to the issue. Her data was later published and she was offered a meeting meeting with Dyson to discuss her findings.
I love the idea of these as a formal science activity for students. It’s an opportunity to learn how sound waves travel, how to measure sound, and how loud is safe. It could be reproduced or tested anywhere. For example, which is loudest: the cafeteria, hallway, school bell, or gym class? Some other ideas are measuring music classes (especially drums), rallies, or special events at the school. Are the fifth graders always the loudest? Are they louder inside or outside?
If the results show a potential unsafe environment, it becomes a natural opportunity for the students to advocate for change – with the data to back it up.
Tools Required
An SPL meter is used to measure loudness (SPL stands for “Sound Pressure Level”). SPL meters can vary greatly in price but for this type of experiment, all you will need is a simple meter with a digital readout. Amazon has many options of meters under $30USD.
There are apps for mobile devices that are SPL meters but accuracy can very. A free app that is known for being accurate is NIOSH.
The main issue on a mobile device is the microphone. Results are more accurate when using an external calibrated microphone. Two mics that were tested and found to be very accurate were:
Dayton Audio iMM-6 Calibrated Measurement Microphone for iPhone, iPad Tablet and Android
- MicW i436 Calibrated Measurement Type 2 External Mini Microphone for iPad, iPhone, and iPod Touch (currently not available to buy new.)
Additionally, the Apple Watch has been tested to be very accurate compared to professional SPL meters (accurate within 1dB).
How to Use an SPL Meter
SPL meters are very easy: point the mic toward the sound source.
When you’re trying to test if a sound is too loud, imagine the microphone as the location where someone’s ear would be. If you are testing a school bell mounted high on a wall, you want to measure the sound level from the location where a student or teacher would be. Testing a bell up close (within inches) would be a good data point, but anything loud and up close requires caution (wearing ear plugs or other hearing protection).
Ideas to Modify the Experiment
- Toys: Can you find toys that are too loud? How much louder are they up close versus a small distance away? (Similar to Sight and Hearing’s yearly toy testing)
- Televisions, screens, and speakers. How loud do you normally listen? How loud is a fight scene versus a calm scene in a video?
Resources
- How Does Sound Travel? Lesson for Kids
- How Decibel Sound Level Meters Work (this is a more technical description but offers good suggestions.)