pattern. This is a result of the cancellation of sound of opposite polarity produced by the front and back sides of the paddle in the plane of the paddle. An estimate of the depth of the null at an angle of 90º to the axis of play can be found by comparing the mean SEL at Point 2 to Point 1 and Point 3 to Point 4. Table 4.2 shows the sound exposure levels for the Foam Quiet ball and Dura 40. The differences in SEL are calculated with a mean for each ball based on the measurements from each half of the playing area. A small correction, Δ L, has been applied to adjust for the difference in distances between the on axis and off axis test points to the acoustic center of the distributed sound source. This is -0.07 dB for Points 1 and 2 and 0.07 dB for Points 3 and 4. Given the consistency of the SEL numbers at Points 1 and 4, it appears the 43.0 dBA SEL for the Foam Quiet ball at Point 3 may be unusually low and the 55.2 dBA SEL for the Dura 40 ball at Point 2 may be unusually high. That would place the actual difference between on axis and off axis SEL at about 5.0 dB for both balls. This is consistent with previous measurements at around four dB and would be expected since the paddle is the primary sound radiator.
Point 1 SEL (dBA)
Point 2 SEL (dBA)
Point 3 SEL (dBA)
Point 4 SEL (dBA)
Point 2 – Point 1 + ΔL (dBA)
Point 3 – Point 4 + ΔL (dBA)
Mean Difference (dBA)
Ball Foam Quiet 40.4 45.8 43.0 40.5 Dura 40 47.4 55.2 51.3 46.2
5.4 7.7
2.6 5.2
3.7 6.3
Table 4.2. Sound Exposure Level Directivity
4.4 Paddle Impact Frequency In order to construct an acoustical model of the site, the sound power of the sources must be known. To find the sound power from the sound exposure levels measured, a hit rate must be established. Table 3.15 summarizes the hit rate for ball and paddle impacts for each of the sound exposure case. The most reliable SEL's will be from the measurements made in the direction of play. Given the background noise level and directivity of the pickleball courts, some paddle impacts may have been missed due to being too close to the background noise level. For this reason only the data from Points 2 and 3 have been averaged. The average hit rate per court used in the acoustical model to calculate the sound powers for the paddle impacts will be 11.6 hits/minute.
28 of 58 Spendiarian & Willis Acoustics & Noise Control LLC
12/15/2019
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