People who live along a heavily traveled road may plant a thick row of bushes, trees or hedges in an attempt to create a sound barrier and reduce the noise of traffic. Locate a home along a well-traveled road that has a thick hedge or foliage between the house and the road. Stand on the road side of the hedge and point your meter toward the road. Sample the peak and average sound levels over a 15-minute period. Stand on the house side of the hedge, point the meter toward the street and again record peak and average sound levels over a 15-minute period. Compare your results and determine whether the hedge is helpful in reducing traffic noise.
Sound waves disperse in all directions from their source. Therefore, the farther you are from the sound, the lower the volume level. Locate a source of constant sound, such as an idling car engine, a swimming pool pump motor or a circular saw. Measure the volume at the source and at a distance of 1 foot, 2 feet, 3 feet, 4 feet and farther until the sound is barely measurable. Determine if there is a mathematical relationship between distance and the volume. (Hint: When sound emanates from a source, it moves out in all directions, forming concentric 3-dimensional circles, or spheres.) The radii of spheres increases as the distance increases from the source, and the sound energy is spread out. The volume decreases inversely proportional to the square of the distance from the source. So, the sound will be 4 times louder at 1 foot from the origin than at 2 feet. And it will be 9 times louder at 3 feet than at 1 foot.
Sound is created by vibrations that occur in the frequency range of human hearing, about 20 hertz (cycles per second) to 20,000 hertz. The wooden body of a violin and an acoustic guitar amplify (make louder) the vibrations of the instrument's strings. Strike a tuning fork and hold it as close as possible to the microphone on a sound level meter without touching it. Record its volume (measured in decibels on the VU meter). Strike the tuning fork again and hold its base against the body of an acoustic guitar. Hold the microphone on the meter as close as you can to the guitar's body and record the volume. The sound will be louder, amplified by the wood.
When you listen to your stereo, various factors alter the sound before it reaches your ears. The stereo amplifier's electronics, speakers, speaker placement and room characteristics -- such as flooring, windows, window treatments and type of furniture -- will cause some frequencies to be accented while others to be diminished. Connect an audio oscillator capable of producing a sine wave to the auxiliary input of your stereo. Position a sound level meter at the location where you usually listen to your stereo, such as your couch. Measure the volume at different frequencies: 20 Hz (hertz), 80, 100, 500, 1,000, 2,000, 4,000, 6,000, 10,000, 12,000 and 15,000. Once you know what frequency bands need to be increased and which decreased, you can purchase an equalizer for your stereo at an audio store to make adjustments so that you have a "flat" or balanced response. (Note: If you do not have access to an audio oscillator, CDs are available that produce tones for just such testing.)