How Pollution Affects Sound Clarity Underwater

Overview

Water pollution can affect several aspects of aquatic environments, underwater location systems, and further scientific study. The purpose of my experiment was to determine whether different types of pollutants affect the clarity and intensity of sound in water. My hypothesis stated that if more solid pollutants, such as plastics and mixed materials, were added to water, then sound would become attenuated because the particles and density of the pollutants would disrupt the movement of sound waves. To test this, three plastic tanks of equal size were filled with 18 quarts of water. One tank served as a control with no pollutants just plain water. A second tank contained plastic pollutants (straws, bottles, plastic bags, and plastic utensils), and a third tank contained mixed pollutants (salt, cornstarch, mulch, leaves, and soap). Sound was produced by striking the side of each tank with a metal spoon while a hydrophone placed at the opposite end recorded the sound using TwistedWave software. Five trials were conducted for each tank. My control tank produced the clearest sound, averaging −12 dB, while my plastic tank averaged −21 dB and the mixed pollutant tank averaged −19 dB. These results show that pollutants reduce sound clarity and intensity underwater. My hypothesis was supported because increased pollutants interfered with sound transmission, causing them to be either scattered, absorbed, or reflected. A limitation of this study was the small tank size, and using a metal spoon as my sound producer. Future research could test sound propagation in larger bodies of water and use an underwater speaker to standardize sound production.

Competition history

• CSEF 2026 Physics & Astronomy (Junior Division) · Entry J-17-01

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