Getting to Grips with Aircraft Noise

Recommendations

Info

9 - A BIT OF THEORY 9.3.5.4. EQUAL ANNOYANCE CONTOURS – NOTION OF PERCEIVED NOISE LEVEL (PNL) In the same philosophy of the one of equivalent loudness curves in phons, K.D. Kryter invented equivalent annoyance or noisiness curves graduated in noys. For each onethird-of-octave band, the acoustic pressure level measured corresponds to a certain level of noisiness n. This notion was developed in order to assess the impact of noise from jet airplane flyovers, accounting this time for the results of an investigation of the reactions of a large number of people. The purpose is to define the so-called Perceived Noise Level (PNL). The following chart illustrates the noy scale: 70 (9.3.5.4-1) In order to get a value that would represent the subjective response of the human ear, the following empirical equation has been developed. It consists in adding the different noy values of the individual one-third-of-octave bands, resulting in what is called the overall noy value N. = nMAX + . 15 ∑ [ n n ] N 0 − (9.3.5.4-2) MAX Where: nmax is the number of noys in the 1/3-octave band having the greatest noy value and ΣΣΣΣn is the sum of the noy values in all bands. Then, the Perceived Noise Level (PNL) is calculated from the overall noy value in the same way the phon and the sone are linked: = 40 + log N , in PNdB (9.3.5.4-3) L PN 2 The PNL is equal to the pressure level that results into the same amount of noisiness for the 1/3 octave band centered on 1000 Hz. Flight Operations Support & Line Assistance Getting to grips with aircraft noise
9.4. NOISE SINGLE EVENT DESCRIPTION Flight Operations Support & Line Assistance Getting to grips with aircraft noise 9 - A BIT OF THEORY 9.4.1. FOREWORD Most of the indices that are used in the assessment of aircraft noise are based upon the A-weighting model. Nonetheless, we must acknowledge that the noise perception (and especially for aircraft) is very subjective and depends on the sensitivity to noise of each person. This is the reason of the existence of many descriptors, the need-to-knows being quoted hereafter. In this section, we will focus only on descriptors for a given event. Further in this book, indices relative to successive events (notion of noise exposure) will be discussed. 9.4.2. A- SOUND PRESSURE LEVEL – (ASPL TERMED LA) This unit is derived from the “standard” SPL (see Section 9 §9.3.5.3) using a filter corresponding to the A-weighting law, in order to consider the human ear perception. It is expressed in dB(A). 9.4.3. EQUIVALENT A-SOUND PRESSURE LEVEL (EASPL TERMED L AEQ,T) In order to take into account the event duration, it is interesting to compute the acoustical A-weighted energy received during the measurement time period T. Dividing the total energy by the time give a single value, that describes a time-varying noise. It is expressed in dB(A). 9.4.4. SOUND EXPOSURE LEVEL (SEL TERMED LAE) In the same way, the SEL is a normalized value of the EASPL, the time period considered being one second. This SEL value represents the “A-weighted” sound level, which, produced during one second, would result in the same EASPL. This allows to get rid of the influence of the measurement period and allows comparison of events of different durations. It is also expressed in dB(A). 9.4.5. SINGLE EVENT NOISE EXPOSURE LEVEL (SENEL) SENEL stands for Single Event Noise Exposure Level. It is derived from SEL in the way that only transient sounds exceeding a certain level are accounted for (typically 65 dB(A)) 71
Page 1 and 2:
Flight Operations Support & Line As
Page 3 and 4:
Page 5 and 6:
Page 7 and 8:
Page 9 and 10:
2.1.2. FAN NOISE Flight Operations
Page 11 and 12:
3.1. ICAO ANNEX 16 VOLUME 1 CHAPTER
Page 13 and 14:
Page 15 and 16:
Page 17 and 18:
3.2.3.5. RECAPITULATIVE TABLE M= Ma
Page 19 and 20:
Page 21 and 22: Flight Operations Support & Line As
Page 33 and 34: 6.1.2.2. SIMULATION OF PROCEDURES F
Page 35 and 36: EXAMPLE OF NLC OUTPUT (Point comput
Page 43 and 44: 7.2. ACTUAL TOW INFLUENCE Flight Op
Page 49 and 50: 8.3.2. MCDU PAGES Flight Operations
Page 55 and 56: 8.6.2. ADAS OUTPUTS Flight Operatio
Page 59 and 60: ⎛ dr ⎞ ⎜⎝ c + ⎟⎠ ' dr
Page 63 and 64: 9.3. PSYCHO-ACOUSTICS Flight Operat
Page 69 and 70: 9.3.5. AIRCRAFT NOISE DESCRIPTION F
Page 71: Flight Operations Support & Line As
Page 81 and 82: 9.5.9. SOME INDICES USED IN DIFFERE
Page 83 and 84: 10.3. ANALYSERS Flight Operations S
Page 87: Flight Operations Support & Line As
show all

Getting to Grips with Aircraft Noise

Create successful ePaper yourself

Delete template?

Save as template?