Sunday 19 July 2009

Second noise survey

In a second noise survey a similar methodology was used to that of the first (record location and noise level separately then correlate manually); however, the dBMeter Pro iPhone App by The Java Works was used in preference to NoiseMeter. This was both because dBMeter Pro offered better functionality (including the ability to measure noise on a decibel scale and export measurements as CSVs via email) and because an update to the NoiseMeter App rendered it unsuitable for noise measurements of the type required by this project - a lesson in the dangers of reliance on third party applications without any service level guarantee.

With aircraft taking off in an westerly direction from the northern runway the levels of noise pollution experienced were universally high, indeed, at a number of locations the maximum sound level of the passing aircraft reached the maximum that can be measured using dBMeter Pro inconjuction with the iPhone - found to be 103.3 dB(lin).

At each location a number of measurements were made and an average calculated. The accuracy of the average value is dependent on the samples used in its calculation forming a representative, random, sample of all aircraft noise events experienced at that location. Multiple readings were used; however, it is likely that the sample size was not sufficient to avoid the average being biased by a greater proportion of large, noisy, aircraft during the period of observation at a given location or small, quieter, aircraft during the period of observation at another. Because of this the average values given in the survey results must be interpreted with care; however, the ability of the phone to measure noise events is a great encouragement.

1 comment:

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