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Introduction A continued and growing concern for the community environment has prompted the Johnson Kart Manufacturing Company of Milwaukee, Wisconsin to undertake an evaluation of noise levels resulting from operation of a commercial go-kart track. This report summarizes results of that evaluation. Sound, Noise, and Decibels Sound is a disturbance in air that travels as a wave having a frequency of between 20 and 20,000 hertz and having an amplitude great enough to be heard. Noise is merely a sound that is, subjectively, unwanted because of intensity, frequency, or location. Just as grass becomes a weed when growing in a garden, even music becomes "noise" if it disturbs one's sleep. Sound is sensed by a microphone which converts the pressure fluctuations of the sound wave to an electrical signal. This signal is conditioned by the circuitry of a sound level meter and the intensity is indicated in units of decibels (dB). The term decibel is defined to be equal to 10 times the logarithm to the base 10 of the ratio of two power quantities. Power can be in watts, horsepower, or, in the case of sound, pressure squared. The advantage of a decibel scale is that smaller numbers can be used in calculations. A disadvantage with this definition, as it relates to sound measurement and analysis, is that sound power cannot be measured directly. The"decibels" indicated on a sound level meter relate to the sound pressure level and not power level. It was noted that, in addition to intensity, sound is further charac- terized by frequency of the sound wave. Since response of the human ear is not the same for all frequencies, various weighting systems have been devised to correlate the sound level meter readings to human response to sound. The "A" weighted scale is presently accepted as resulting in the closest correlation. Table 1 shows the amount of attenuation or amplification of sound pressure level over the audible frequency range for the A weighted scale. Table 2 shows average noise levels for some sources typically encountered in a community enviro- nment. An interesting point of Table 2 is the human response to loudness. Technically, doubling the sound pressure level causes a 3dB increase in reading or a 6dB increase in sound power level. However as shown in Table 2, the human ear doesn't perceive a sound as being twice as loud until the difference in sound pressure level approaches 10dB. Test Program Test procedures followed were in general accord with accepted industry standards as defined by the Society of Automotive Engineers in SAE J 331 and SAE J 986. The sound level meter was a Bruel & Kjoerr Type 2209 equipped with a condensor microphone (Bruel & Kjoerr Type 4165). Instrument calibration was accomplished on site at the time of test using a General Radio Model 1562-Acalibrator. Accuracy of calibration is traceable to the National Bureau of Standards. Instruments conform to requirements of SAE J 184 and American National Standards Institute Specifications ANSI S1.4 - 1971 and ANSI S1.11 - 1966. The test sit chosen was the kart track of Johnson Park, Milwaukee, Wiscon- sin. Track layout and microphone positions are shown in figure 1. Nine