ANASE ‘Attitudes to Noise from Aviation Sources in England’ reportFebruary 10, 2008 at 3:01 am | Posted in Decibels, Frequency, Heathrow, Heathrow expansion, Levels, Noise, Quality of life, Randomness | Leave a comment
Would you be willing to pay to reduce aircraft noise that you objected to in the first place?! See below. The Executive Summary of the ANASE ‘Attitudes to Noise from Aviation Sources in England‘ report commissioned by the Department for Transport concluded (and I am not expecting you to read this, as it is an example of the degree to which the wrong things are being studied, so just skim to my remark at the end):
Re-assessing Attitudes to Aircraft Noise in England
1.4.1 Analysis of the ANASE survey data has shown that as the sound level indicator LAeq increases, the annoyance levels of respondents also increase, and that a large proportion of measured variation in annoyance can be accounted for by LAeq. However for a given LAeq, there is a range of reported annoyance indicating that annoyance is not determined solely by the amount of aircraft sound as measured by LAeq.
1.4.2 Our analysis showed that respondent’s household income and SEG were the most important influences on the level of annoyance. Once these factors are accounted for there are no further significant location effects (ie those affected by aircraft at Heathrow, for a given LAeq and income, are no more annoyed than those living close to other airports covered in the study).
1.4.3 For both this study (ANASE survey work carried out in 2005), and the ANIS survey (undertaken in 1982), LAeq is effective at explaining much of the variation in respondents’ reported annoyance. However, this comparison has also shown that for the same amount of aircraft noise, measured in LAeq, people are more annoyed in 2005 than they were in 1982. For an LAeq of 57 (identified in the DORA report as the onset of significant annoyance), the modelled value of annoyance for ANIS is 39 (slightly higher than “a little annoyed” on the ANIS scale), whereas for ANASE it is 53 (somewhat higher than “moderately annoyed” on the ANASE scale).
1.4.4 If LAeq is an appropriate proxy measure of annoyance, one possible explanation of the increase in reported annoyance for a given LAeq, between 1982 and 2005, may be a combination of changes in income/standard of living (which were significant cross-sectional factors in ANASE) and changes in attitudes within society. This view is supported by social trend data. While both income and taste effects are likely to be important, it is not possible to identify their relative strength from our research: they are, of course, closely correlated.
1.4.5 An alternative hypothesis is that LAeq is not the appropriate measure, and that annoyance in both studies would correlate better with another sound level indicator (as discussed below).
1.4.6 The SP results have shown people to be much more sensitive to aircraft noise at night (particularly around midnight and the early hours thereafter). In contrast, people are least sensitive to aircraft noise in the morning and early afternoon. Ideally, therefore, a metric that reflects attitudes to aircraft noise should reflect these time of day sensitivities better than the existing LAeq – which does not weight by time of day.
Re-assessing their Correlation with LAeq
1.4.7 Models were estimated which predicted mean annoyance values using LAeq. These showed that the best fitting model, with around three-quarters of the variation explained, is a linear relationship between annoyance and LAeq. However a logistic model, which produces an almost identical fit to the basic linear model, has the added advantage that it is bounded to the mean annoyance scores.
1.4.8 The modelling work also showed that respondents were less sensitive to changes in sound level below 42 LAeq and above 59 LAeq, adding support to a logistic form. There was no threshold, or discontinuity, in the relationship between mean annoyance and LAeq.
1.4.9 The ANIS and ANASE surveys allowed us to compare the correlation of reported annoyance with LAeq at two points in time. Over the period between the two surveys, there has been a substantial change in the make-up of aircraft, with many more aircraft in 2005 but with a lower (average) sound level than in 1982.
1.4.10 We found that the relationship between annoyance and sound level was strong for ANIS, but there was little relationship between annoyance and aircraft numbers. The converse was the case for ANASE. Therefore, the changes in reported annoyance for a given LAeq between 1982 and 2005 may reflect the changes in the composition of number and sound level that people are exposed to, suggesting a different formulation to that implied by LAeq.
1.4.11 An NNI-type measure gives a larger weight to the number of aircraft relative to the sound level than LAeq, and comparisons of the ANIS and ANASE mean annoyance against the NNI-type metric showed that the two datasets were much more closely aligned with the NNI-type measure than LAeq.
1.4.12 However, the relationship between reported annoyance, sound level and the number of aircraft has not been stable over time. The weight on aircraft numbers (relative to sound level) has risen from 6 in ANIS to over 20 in ANASE, so the contribution of aircraft numbers to annoyance has increased quite markedly. Because of its instability over time, use of the LAeq measure to predict future levels of annoyance may be misleading. Although the NNI- type index is also not stable over time, with the later ANASE result giving greater weight to aircraft numbers, the ANASE result is relatively insensitive to a weight greater than 20, so an NNI type measure may provide a better tool for predicting annoyance from aircraft noise.
1.4.13 Overall, we consider that while LAeq continues to be a good proxy for measuring community annoyance at a point in time, the relationship between LAeq and annoyance is not stable over time. An NNI – type measure appears to offer a stronger basis than LAeq for estimating future levels of annoyance in response to changing numbers and types of aircraft.
Time of Day and Willingness to Pay to Reduce Aircraft Noise
1.4.14 The results of the SP survey have shown strong internal consistency and statistical validity, with a clear indication that aircraft SEL, aircraft type, time of day and personal characteristics (in particular household income) influence annoyance and willingness to pay to reduce it.
1.4.15 As a proxy for predicting changes in community annoyance in relation to a change from the current noise environment, our SP research supports the view that the role of number of events needs to be higher than that implied in the LAeq index.
1.4.16 The SP results have shown people to be more sensitive to aircraft noise at night (particularly around midnight and the early hours thereafter). In contrast, people are least sensitive to aircraft noise in the morning and early afternoon. These time-of-day sensitivities seem intuitively plausible and are also comparable with other research.
1.4.17 Unfortunately, despite the internal consistency, the implied valuations from the SP are much higher then may be considered plausible, when translated into a “per dB” value.
1.4.18 Valuations were also obtained from the CVM analysis. The implied willingness to pay to remove all aircraft noise was £3.80 – £11.50 per annum per dB reduction in LAeq for respondents, depending upon household income level. However, although this value is in the same ball-park as recent valuations based upon Hedonic Pricing, we have some reservations about the data, both because of the large proportion of respondents professing zero willingness to pay, and the apparent influence of the initial starting point in the “bidding” process.
1.4.19 Overall, therefore, we do not think that the valuations from either method are safe, and it will probably be necessary to rely on sources based on Hedonic Pricing. Nonetheless, the relative valuations – particularly those relating to time of day variation – can be used.
1.4.20 The ANASE study has produced a range of interesting results from the survey data collected, and could form the basis for future research to address a number of issues raised. Some of the issues can be investigated with more detailed analysis of the current data, whilst others will require supplementary data collection.
The Government is ignoring these findings.
Furthermore, the report compares sound levels averaged over a period, and we used to have Concorde going over once every four hours. It was very loud but (to me) impressive. We would stop, look up and admire that marvel of engineering, and then carry on. Now, Concorde has gone, so any comparisons of average noise levels with previous years are rather misleading if they do not first draw attention to this significant change in makeup of noise sources.
As far as I can see, this report does not take into account the frequency of noise disturbances—only the dB levels averaged over an unspecified period of time. With Concorde, you could at least let young kids nap sometime during the four-hour quieter period. Not so now.
Chinese water torture is not related to the volume of water dripped: it is the frequency and randomness that would drive one insane!