A-D7

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EUROPEAN COMMISSION

DG RESEARCH

SIXTH FRAMEWORK PROGRAMME

PRIORITY 6

SUSTAINABLE DEVELOPMENT, GLOBAL CHANGE & ECOSYSTEMS

INTEGRATED PROJECT – CONTRACT N. 516288

Sub-project A 'Annoyance'

Deliverable A.D7: month 36

Transfer of evaluation of noise attenuation measures developed within the IP

Deliverable no. e.g. A.D5

Dissemination level e.g. Partners and Public

Work Package A1.3: Guidelines for noise reduction by traffic management.

Author(s) Barbara Griefahn

Co-author(s) Truls Gjestland, Anna Preis

Status (F: final, D: draft) e.g. D5_31.08.2007

File Name e.g. SILENCE_A.D5_2_IFADO.doc

Project Start Date and Duration 31 August 2007, 30 months

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A2: Annoyance of residents and evaluation of develop-ments within SILENCE

Workpackage A2 aimed at

− the determination of annoyance in urban areas,

− the evaluation of attenuation measures developed within the SILENCE IP.

A2.2: Evaluation of abatement measures developed within 'SI-LENCE'.

This task focused on the evaluation of attenuation measures developed by SILENCEpartners by comparing original and resulting noises with psychoacoustic listeningtests.

1 Evaluation of developments within SILENCE IP

Evaluation of the simulation tool VAMPPASS

During the joint SPA / SPB meeting (25th

of June, 2007) where the pass-by noisesimulation software developed in SPB has been demonstrated to SPA partners thefollowing was decided:

• Three types of sound samples: A – recorded sound samples of the pass-bys of an AGC train in Diesel and in electric mode at 30 and 80km/h, B – simulated soundsamples of the same pass-bys, C – simulated sound samples of optimized con-figurations according to the potential of source reductions given by the manufac-tures, SNCF will provide IfADo and UAM with the simulated sound samples of

family B and C.• As mentioned in BD7 the noise reduction achieved with the optimized sources is

not very high in terms of sound level (dB A). It may be possible that this indicator isnot relevant.

• A subjective study can be carried out to assess the difference in subjective judg-ments of the sounds especially in annoyance.

• Two tests will be performedTest 1 - to judge the difference between the sound samples andTest 2 – to show the annoyance scale of all the sound samples using the ICBENscale.

The noise reduction achieved with the optimized sources expressed in sound level(dBA) is presented in Fig. 1 (Table 22 from BD7). The L AeqT values presented in thistable were the same as in two subjective experiments performed in UAM.

1.1 TEST 1

The aim of Test 1 was to find out if the modified sound samples are different from thestandard case.

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Fig. 1. Simulated sound samples of family B and C with the L AeqT

used in two subjective studies performed at UAM

1.1.1 Objective analysis

An objective analysis of 20 stimuli used in the psychoacoustic experiments was per-formed using Artemis software. For each stimulus (for adjusted values of L AeqT fromFig.1.) loudness, roughness, sharpness and tonality were calculated and presentedin Table 1.

1.1.2 Subjects

19 listeners participated in the experiment. They were 19 to 27 years old. All listenersqualified as having normal hearing (defined as the audiometric threshold of 20 dB

HL, or better, for the frequency range from 250 to 8000 Hz, according to ANSI stan-dard ) and were paid for their participation.

1.1.3 Procedure

All stimuli were presented at the sound levels indicated in the first column of Table 1.The stimuli were organized in pairs. In each pair there was a standard stimulus likeD30kphstd, D80kphstd, E30kphstd, E80kphstd for two different types of trains (D andE) and two different velocity (30kph and 80 kph). All possible pairs were presentedrandomly to the subjects. Each pair was presented 12 times to the listeners. The subjects' task was to answer the following question: You will listen to two sounds pre-

sented in a pair, please indicate - on the paper - which sound in a pair is moreannoying.

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Table 1: Sound samples

Sound sampleSoundlevel Loudness Roughness Sharpness Tonality

dBA sone asper acum tu

D30kphstd_mono ( 0.00-11.87 s) 68,7 27,1 2,32 2,21 0,258D30_noisy_mono ( 0.00-11.87 s) 69,8 28,5 2,43 2,18 0,26

D30kph_exh_opt_mono ( 0.00-11.87 s) 68,6 27,3 2,28 2,16 0,273

D30kph_cool_opt_mono ( 0.00-11.87 s) 67,5 25,9 2,27 2,14 0,247

D30kph_damperv_mono ( 0.00-11.87 s) 68,4 27,6 2,23 2,22 0,298

D30kph_quietrn_mono ( 0.00-11.87 s) 68 26,2 2,2 2,16 0,277

D30kph_quiet_mono ( 0.00-11.87 s) 67 25,4 2,21 2,12 0,244

D80kphstd_mono ( 0.00- 4.55 s) 76,2 41 3,05 2,81 0,22

D80kph_noisy_mono ( 0.00- 4.55 s) 77,1 42,5 3,1 2,83 0,219

D80kph_exh_opt_mono ( 0.00- 4.55 s) 76,4 41,6 3,04 2,82 0,208

D80kph_cool_opt_mono ( 0.00- 4.55 s) 74,9 38,4 2,96 2,78 0,208

D80kph_damperv_mono ( 0.00- 4.55 s) 75,2 39,8 2,88 2,84 0,223D80kph_quietrn_mono ( 0.00- 4.55 s) 74,7 37,9 2,77 2,66 0,243

D80kph_quiet_mono ( 0.00- 4.55 s) 72,9 35,1 2,7 2,64 0,233

E30kphstd_mono ( 0.00-11.87 s) 61,8 14,4 1,97 2,23 0,042

E30kph_damperv_mono ( 0.00-11.87 s) 58,1 12,8 1,75 2,33 0,0396

E30kph_quietrn_mono ( 0.00-11.87 s) 57,3 11,2 1,62 2,07 0,0537

E80kphstd_mono ( 0.00- 4.55 s) 72,2 27 2,75 2,91 0,0426

E80kph_damperv_mono ( 0.00- 4.55 s) 68,8 24,3 2,51 2,98 0,0566

E80kph_quietrn_mono ( 0.00- 4.55 s) 67,4 21,1 2,32 2,64 0,0554

1.1.4 Results of the psychoacoustic experiment – Test 1

For the diesel mode, and 30kph the six sound samples were compared with thestandard case.

The results of this comparison are presented in Fig. 2. In pair 1 the test stimulus wasthe noisy case, in pair 2 – exhaust, in pair 3 – cooling, in pair 4 – rail dampers, in par 5 – rail and wheel dampers and in pair 6 – global.

The results of paired comparisons for diesel mode, 80kph, are presented in the simi-lar way as for the diesel mode, 30kph - in Fig. 3. In Figs. 2, 3, and 6 on y-axis there is% of responses “more annoying sound in a pair”.

The differences between the 1/3 octave band spectra of standard case and “cooling”and “global“ modifications, for diesel mode 30kph, are shown in Fig. 4. The localmaximum around 300 Hz which exists in standard case disappeared in the 3 and 4sound samples.

For diesel mode 80kph, a flat spectrum envelope for sound samples 4 and 5 in a fre-quency range 300-1000Hz is responsible for reduction of noise annoyance of thesesound samples compared to the standard sound sample. It is shown in Fig 5.

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0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

1 2 3 4 5 6

standard

test

Fig. 2. Diesel mode (30kph ) – results of pairs comparison for six stimuli. Test stimulusin each pair was: 1 – noisy case, 2 – exhaust, 3 – cooling, 4 – rail dampers,

5 – rail and wheel dampers, 6 – global.

0,0

10,0

20,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

1 2 3 4 5 6

standard

test

Fig. 3. Diesel mode (80kph ) – results of pairs comparison for six stimuli. Test stimulusin each pair was: 1 – noisy case, 2 – exhaust, 3 – cooling, 4 – rail dampers, 5 – rail and

wheel dampers, 6 – global.

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(a) (b)

(c)

Fig. 4. Diesel mode 30kph - 1/3 octave band spectra of sound samples:cooling (a), global (b), standard case (c).

(a) (b)

(c)

Fig. 5. Diesel mode 80kph - 1/3 octave band spectra of sound samples: rail dampers (a),rail and wheel dampers(b), standard case (c).

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For the electric mode, for both velocities 30kph and 80khp, two sound samples werecompared with the standard case. In pair 1 a test stimulus was rail dampers and inpair 2 – rail and wheel dampers. In Fig. 6. results for both velocities are presentedtogether.

0,0

10,020,0

30,0

40,0

50,0

60,0

70,0

80,0

90,0

100,0

1 2 3 4

standard

test

Fig. 6. Electric mode – results of pairs comparison for 2 stimuli and 2 velocities. Test stimulus

in pairs 1 and 3 was rail dampers and in pairs 2 and 4 rail and wheel dampers. The resultsfor pairs 1 and 2 are obtained for the 30kph, and 3 and 4 for 80kph.

1.2 Test 2The aim of the Test 2 was to evaluate all sound samples with annoyance scales.

1.2.1 Procedure

Each of the 20 resulting different stimuli was presented 20 times. The stimuli werepresented in random order. The whole experiment was carried out in 5 minutes longsessions – 4 sessions per day. Listeners judged the annoyance of each stimulus us-ing a 11 point scale (0-10). The scale used in this study is recommended for noisesurveys by ICBEN.

The subjects were given the following instruction: what number from zero to tenbest shows how much you are bothered, disturbed, or annoyed by noise? If you are not at all annoyed choose zero, if you are extremely annoyed chooseten, if you are somewhere in between choose a number between zero and ten.

1.2.2 Results of the psychoacoustic experiment – Test 2

In Figs. 7 and 8 the results of annoyance ratings of all sound samples are presentedon the ICBEN scale.

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5,0

5,5

6,0

6,5

7,0

7,5

8,0

8,5

9,0

n o i s y

s t d

d a m p e

r v

e x t o

p t

c o o l

o p t

q u i t e

r n q u i e t

I C B E N s c a

l e

30kph

80kph

Fig. 7. Annoyance ratings on ICBEN scale of the diesel mode for two velocities.

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

std damperv quitern

I C B E N s

c a l e

30kph80kph

Fig. 8. Annoyance ratings on ICBEN scale of the electric mode for two velocities.

Data of the 20 measurements for each velocity and each modification were averagedfor each subject. The results for Diesel and electric train were analyzed separately.The 2-factorial (2 (velocity) * 7 (modification) – for Diesel train and 2 (velocity) * 3(modification) for the electric train) within-subject analyses of variance with repeatedmeasurements were conducted for each type of train.

In a first step, data were checked for normality by means of the ratio of skewnessand kurtosis to the corresponding standard errors. Data indicated that there were nosubstantial deviations from normality. Since the assumption of sphericity was not met

for the factors ‘velocity’ and ‘modification’, - for Diesel train and factor ‘velocity’ for electric train adjustment of the degrees of freedom was made according to Green-house-Geisser.

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The ‘velocity’ was a significant factor for both types of trains (Diesel: F(6,18) = 32.34;p<0.05 and Electric: F(1,18) = 98.6;p<0.05). Modification was also a significant factor for both types of trains (Diesel: F(6,108) = 30.0; p<0.05 and Electric: F(1,36) =23.55;p<0.05). The paired comparisons showed significant differences between allmodifications for the electric train. For the Diesel train no significant differences were

found between pairs: cool_opt and quietrn (p = 0.23), damperv and exh_opt (p =0.61), damperv and std (p = 0.55), exh_opt and std (p = 0.83). This means, that sig-nals: std, exh_opt and damperv were judged as equally annoying.

0,0

1,0

2,0

3,0

4,0

5,0

6,0

7,0

8,0

9,0

10,0

noisy std damperv ext opt cool opt quitern quiet

Sound sample

I C B E N s

c a l e

Diesel 30kphDiesel 80kphElectric 30kphElectric 80k h

Fig. 9. Annoyance ratings for all investigated sound samples.

The results of two subjective tests together with the noise reduction presented in BD7provided by SNCF is shown in Table 2.

Table 2. Results of subjective tests and noise reduction in dB A

Pair of sounds

Diesel 30kph Diesel 80kph Electric 30kph Electric 80kph

dBA

SNCF

%

T. 1

Icben

T. 2

dBA

SNCF

%

T. 1

Icben

T. 2

dBA

SNCF

%

T. 1

Icben

T. 2

dBA

SNCF

%

T. 1

Icben

T. 2

stdnois

68.769.8

46.453.6

6.97.1

76.277.1

31.868.2

8.58.6

stdexh

68.768.6

49.051.0

6.96.9

76.276.4

50.050.0

8.58.5

stdcool

68.767.5

69.330.7

6.96.9

76.274.9

77.122.9

8.58.1

stddamperv

68.768.4

46.453.6

6.97.0

76.275.2

63.037.0

8.58.4

61.958.2

69.031.0

3.83.5

72.268.9

77.122.9

5.95.6

stdquietrn

68.768.0

50.549.5

6.96.8

76.274.7

75.025.0

8.57.9

61.957.3

80.219.8

3.83.2

72.267.4

93.07.0

5.95.1

std

quiet

68.7

67.0

69.3

30.7

6.9

6.7

76.2

72.9

81.3

18.7

8.5

7.4

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1.3 Conclusions

From Test 1:

• For Diesel mode 30kph at least 1.2 dBA reduction in sound level is needed tobe noticed as “less annoying sound” in a pair comparison test.

• For Diesel mode 80kph 1.0 dBA reduction in sound level is needed to be no-ticed as “less annoying sound” in a pair comparison test

• In Table 1 the sound samples perceived as different are marked by color “yel-low”. It can be seen that only loudness correlates with the results of subjectiveassessment in pair comparison test. The changes in sound spectra presentedin Fig. 4 for 30kph and in Fig. 5 for 80kph are responsible for the differencesperceived by subjects.

• For Electric mode and both velocities the reduction in sound level was bigenough to produce the sensation of “less annoying sound in a pair”.

From Test 2:

• For Electric mode and both velocities there is significant difference in allsound samples. It means that differences in ICBEN scale as small as 0.3 areperceived by the subjects.

• For Diesel mode for both velocities sound samples are perceived as been dif-ferent on ICBEN scale if the difference was equal or bigger than 0.3 .

• There was no difference in annoyance between the std, exh and damperv sound samples.

The results form both test are similar with one exception. According to Test 1 sound

sample damperv is different form sound sample std, while in Test 2 there is no

significant difference in annoyance between these two sound sample. It suggests that

more then 1 dBA reduction in sound level is needed to noticed a difference in

annoyance between two sound samples.

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2 Squeal tram noise annoyance

The aim of this study is a subjective verification of the ISO 1996-2 standard. The cor-

rection K1 (expressed in dB) for noise with tonal components, which was proposed

by this standard, was calculated for squeal tram noise. The annoyance caused by

passing trams was also assessed in a psychoacoustic experiment (using a two alter-native forced choice - 2AFC method with an adaptive procedure). Subjects listened

to binaurally recorded tram noise and compared how annoying it is, both before and

after the acoustical treatment of squealing segments of the railway track curves (con-

siderable reduction of squeal was achieved by mounting special lubricating devices).

Equally annoying pairs of tram noises before and after treatment were then used to

estimate the level of correction for the squeal. The correction obtained from the psy-

choacoustic experiment was then compared with the correction calculated based on

the ISO 1996-2 standard. In addition, the dependence of the objective acoustical pa-

rameters of the squeal tram noise on perceived annoyance was investigated.

2.1 Introduction

The main source of tram noise is the interaction between wheel and rail. Regarding

the noise generation mechanism three different types of tram noise can be specified:

rolling noise, impact noise and squeal noise [1, 2]. The first type of noise is always

present during tram motion. The second type of noise is concerned with track discon-

tinuity and other physical damages to the track surface. The third type of tram noise

is concerned with the generation of very high-level tonal components on rail-track

curves with a relatively small radius.

In the present study annoyance caused by the last type of noise is investigated. The

main reason for this tonal noise is so-called wheel “crawling”. The tram wheels are

usually mounted on two–axle boogies. On the rail-track curves one pair of wheels

usually is not tangential to the track, and wheel crawling occurs. On the rail-track

curve, speed of the outer wheel should be higher than the speed of inner wheel.

Tram driving wheels are typically fixed on a common axle, so the rolling speed of

each wheel is the same and wheel crawling occurs. The second reason for the

squealing is the friction between the vertical surfaces of the wheel and the vertical

surface of rail which can occur on tail-track curves.

Squealing can be eliminated by the appropriate construction of wheel suspension.

For already existing trams a solution employing specially designed lubricating de-

vices can be used. Such a solution was used in this study. Several meters before the

beginning of a rail track curve a special device with grease was mounted. This device

lubricates the tram wheels. The amount of grease is small, so as to avoid any prob-

lems with braking or accelerating. A typical example of FFT and the 1/3 octave spec-

trum of a squeal tram noise is presented in Fig. 1.

The squealing is extremely annoying. This annoyance is concerned with a large

number of mid and high-frequency, high-level tonal components. According to the

ISO 1996-2 standard [3], a correction K1 should be added to the measured LAeqT of this type of sound.

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a) b)

Figure 1. The spectrum of a typical tram squeal . a) narrowband (12 Hz frequencyresolution) FFT spectrum, b) 1/3 octave spectrum.

The rules for calculating the value of correction K1 are as follows. First, if the level of

one or more frequency bands of the 1/3 octave spectrum is 5 dB or higher than the

level of an adjacent frequency bands, then the value of correction K1 should be 5 to6 dB. Second, in case there is no 5 dB difference between adjacent frequency bands,

but squealing is still perceived, a narrowband analysis should be performed. If any

tonal component can be found, the correction value should be from 2 to 3 dB. In the

ISO 1996-2 standard the correction factor is independent of the magnitude of tonal

components present in the noise.

In this study, the correction factor proposed by this standard was validated subjec-

tively, by comparing tram noises with squealing and without squealing. This was

done by subjective annoyance equalization of noises with and without squealing. For

an equally annoying pair of tram noises, the difference in LAeqT between the two

noises was calculated. This difference was then compared with the correction pro-

posed by the ISO 1996-2 standard.

From a perceptual point of view, the tonal components that are present in a squeal-

ing noise evoke not only the sensation of tonality but also the sensation of sharp-

ness. It is expected that the value of correction K1 calculated for squealing should

correlated to these two factors, tonality and sharpness. In order to find the relation-

ship between “subjective” correction and physical characteristic of a squealing noise,

the sharpness and tonality were calculated for each stimulus.

2.2 Methods and Material

Stimuli and equipment. Binaurally recorded tram noises were used as stimuli in the

psychoacoustic experiment. The noises were recorded with a Neumann KU100

dummy head and a Sony TCD-D10 PRO II DAT recorder, with sampling frequency of

48 kHz and 16 bits resolution. The duration of each stimulus was 3 seconds. Passing

trams were recorded on a rail-track curve with a radius approximately of 15 meters.

Two types of trams were recorded: 105N (a Polish tram – 6 passages before and 6

after mounting lubricating devices) and TARTA (a Czech tram – 4 passages before

and 4 after). The reduced spectra of tram squeals are presented in Fig. 2. Each tram

squeal recording fulfills the 5 dB criteria for the K1 correction value proposed by ISO1996-2. Thus all noises are considered as squeals.

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a) b)

Figure 2. The reduced spectra of a recorded squeal tram noises: a) 105N trams, b) Tatra trams.

The stimuli were presented to the listener via Sennheiser HD600 headphones. Theexperiment was controlled by computer. The listener was sitting in a specially de-

signed soundproof chamber. The computer was placed outside the chamber duringthe experimental sessions. Only the computer screen and mouse were placed insideto enable the collection of the subject’s responses.

Procedure. Annoyance of tram noise with and without squeal components wasequalized by using a ‘two alternative forced choice procedure’ (2AFC) with a 2-down,1-up adaptive algorithm. Stimuli were presented in pairs. Each pair contained squealand non-squeal tram noise, presented in a random order. Subjects were asked tochoose which of the two tram noises in the pair is more annoying. In half of the trialssound pressure level of the stimulus without squeals was initially set at a level whichcaused significantly greater annoyance. In the second half of the trials the stimulus

without squeals was initially set at a level corresponding to significantly lower annoy-ance. In both sequences the level of the test stimulus (without squeals) was modifiedby the adaptive algorithm. As a result of this experiment, equally annoying pairs of noises, with and without squeals, were obtained.

Subjects. Seven listeners participated in the pychoacoustic experiment. The listen-ers were 20 to 25 years old. All were students of the Faculty of Physics, AdamMickiewicz University. All listeners qualified as having normal hearing (normal hear-ing was defined as the audiometric threshold of 20 dB HL or better for the frequencyrange from 250 to 8000 Hz [4]).

2.3 Results As a result of the psychoacoustic experiment, 10 pairs of equally annoying squeal

and non-squeal tram noises were obtained for 7 subjects. Pairs 1-6 were the 105N

tram noises, and pairs 7-10 were Tatra tram noises. Since the differences between

subjects were not statistically significant, the results were averaged over the sub-

jects. The main result of this experiment is the difference in the A-weighted equiva-

lent sound pressure level LAeqT. This difference was calculated for each pair of

noises and is presented in Fig. 3.

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Figure 3. Differences in A-weighted equivalent sound pressure level for equally annoyingpairs of noises averaged over 7 listeners.

The tram noises with squeals are perceived to be equally annoying as tram noises

without squeals, when their LAeqT are higher (in a range of 2.2 to 6.6 dB – depend-

ing on the pair compared ). The average difference is 3.3 dB for 105N, and 5.1 dB for

the Tatra tram.

b)a)

Figure 4. The FFT spectra (a) and sharpness (b) of equally annoying squeal andnon-squeal tram noises (pair no. 9).

The differences between equally annoying tram noises with and without squeals

were identified in an FFT spectrum and sharpness vs time pattern (see pair no. 9 as

an example in Fig 4). For each stimulus the average sharpness (according to Auers

model) and tonality were also calculated. These factors are presented in Fig. 5.

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a) b)

Figure 5. Results of objective analysis: sharpness (a) and tonality (b) as the functionof difference in LAeqT. Each data point corresponds to one signal pair.

Regarding the difference between the noises generated by trams 105N and Tatra(see Fig. 2) the sharpness and tonality were analyzed separately for each type of tram. These factors were analyzed as a function of the difference in LAeqT. A corre-lation was found between sharpness and ∆LAeqT. Sharpness as a function of ∆LAeqT is presented in Fig. 6 for two types of trams separately. No correlation wasfound between tonality and ∆LAeqT.

a) b)

Figure 6. Results of objective analysis: sharpness as a function of ∆LAeqT for 105N (a) and

Tatra (b) trams. The solid line represents linear fit to experimental data.

a) b)

2.4 Conclusions

A different value of ∆LAeqT was found for different signals. The subjective LAeqTcorrection factors for annoyance obtained in this study varied from 2.2 – 6.6 dB. Thesignals used in the study differed in their physical parameters. Particularly, the mag-nitudes of squeal – tonal components – were different among compared pairs. Therewere also significant differences in the noise of each type of tram (see Fig. 2). For the105N tram the maximal tonal component occurred for 500 Hz, whereas for the Tatra

the maximal component was about 1500 Hz. Such a result suggests that the tonalcorrection proposed by the ISO 1996-2:1999 standard should depend on the magni-tudes and frequencies of tonal components. Since the obtained differences in LAeqT

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are highly correlated with sharpness it seems that sharpness can be used as a scal-ing factor for correction proposed by the ISO 1996-2:1999 standard. Surprisingly, nocorrelation was found between tonality and differences in LAeqT. This finding re-quires further investigations.

2.5 REFERENCES

[1] M. A. Heckl and I. D. Abrahams, “Curve squeal of train wheels, part 1: Mathe-matical model for its generation,” Journal of Sound and Vibration (2000) 229(3),669-693.

[2] J.J. Kalker, F. Periard, “Wheel-rail noise: impact, random, corrugation and tonalnoise,” Wear 19 (1996), 184-187.

[3] ISO 1996-2 “Acoustic – Description and measurement of environmental noise –Part 2: Acquisition of data pertinent to land use,” (International Organization for Standarization, Geneve, Switzerland)

[4] ANSI S3.6-1996, "Specifications for Audiometers," (American National Stan-dards Institute, New York)

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3 Just noticeable differences in annoyance judgment,depending on the sound source’s velocity

ABSTRACTBoth the sound power level and the time pattern of a noise generated by a movingpassenger car strongly depend on its velocity. Changes in these two factors affectannoyance ratings. The relationship between annoyance and the velocity of a pas-senger car was investigated using a binaurally simulated car pass-by. The soundsource model (a passenger car) used in the simulation was developed within theEuropean project “Harmonoise”. Air-absorption and ground effect were accounted for in a simulated car pass-by. The annoyance caused by a noise generated by a pas-senger car moving at velocities from 25 to 130 km/h was investigated in two psycho-acoustic experiments. In Experiment I participants judged noise annoyance using a11 point (0-10) scale. A linear relationship between annoyance rating and velocitywas found as a result of this experiment. The annoyance ratings were then comparedwith the calculated characteristics of the stimuli, such as: loudness, sharpness,LpAmax and LAE. A linear relationship has also been found between the calculatedloudness and velocity. In Experiment II, using the method of constant stimuli, minimaldifferences in velocity corresponding to the just noticeable differences (JND’s) in an-noyance were collected. The minimal velocity differences corresponding to JND inannoyance obtained for three different reference velocities (50, 90 and 110 km/h) arein the range of 11 – 15 km/h.

1 Introduction

The reduction of annoyance caused by traffic noise has become the main topic of many research projects. Effective traffic noise abatement should take into accountthe influence of different traffic flow parameters and source parameters on the per-ceptions of annoyance caused by traffic flow. This problem should be solved in twoseparate ways. Firstly – investigation should focus on how changes in the parame-ters (the velocity, power spectrum, distance from the road) of a single source’s pa-rameters affect annoyance. Then the relationship between traffic flow parameters(the number of vehicles in the time unit, the distribution of vehicles within the timeunit, the distribution of vehicles velocity, etc.) and annoyance judgements should bestudied.

In the present paper, the noise annoyance caused by a single vehicle (a passenger car) is investigated. In the case of a noise generated by a single car passage, thetotal sound power level, the shape of the power spectrum, as well as the time pat-tern, all change with its velocity. These dependencies are well described in the Har-monoise road traffic noise prediction and calculation model [1]. The question arises –how do these multiple changes affect the annoyance level of a noise generated by asingle car? Another important question is – what are the minimal changes in velocitythat produce just noticeable changes in annoyance? Answering these questionsshould be very helpful when planning appropriate noise abatement methods. Twopsychoacoustic experiments were preformed in the present study in order to answer these questions. In Experiment I the relationship between the velocity of a passenger

car and its annoyance rating was determined for the velocity range of 30-110 km/h.In Experiment II a minimal difference in velocity corresponding to just noticeable

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changes in the annoyance (velocity-annoyance JND’s) was determined for three ref-erence velocities: 50, 90 and 110 km/h.

2 Method

Stimuli and equipmentIn the present study, binaurally simulated passenger car pass-bys were used asstimuli. The car moved along a line in front of a participant’s head at the distance of 7.5m. In the simulation process, assuming compacted ground between the road andthe participant, a one-impedance ground-effect model proposed by Makarewicz [2]was applied. Air absorption was applied according to the ISO 9613-1:1993 [3] stan-dard, with the assumed air temperature at 20

OC and relative humidity at 70%. The

sound source model was implemented according to the Harmonoise model. A de-tailed description of the simulation method was presented by Kaczmarek (2007) [4,5].

The velocities of the simulated pass-bys were presented in 5 km/h steps and cover the range of 20 to 130 km/h. The 1/3 octave power spectra of the noises generatedby these passages are presented in Fig. 1.

65

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95

100

10 100 1000 10000

f [Hz]

L w [ d B ]

20 km/h

40 km/h

60 km/h

80 km/h

100 km/h

130 km/h

Figure 1. Sound power spectra calculated according to the Harmonoise model

for velocities from 20 to 130 km/h.

The stimuli were of 4 seconds duration. For each velocity the point of closest ap-

proach was in the middle of the observation interval (2s).

Objective analysis of all the stimuli was performed with a help of Artemis Analyzer software. The maximum A-weighted sound pressure level, (LpAmax), and the percen-tile values of loudness, (N10), and sharpness, (S10), were calculated for each valueof the investigated velocity. The results of these calculations are presented in Fig. 2a- 2c. Additionally, similar calculations were performed for the sound exposure level,(L AE), average loudness, (N), and average sharpness, (S) and presented in Fig. 2d-2f.

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a) d)

b) e)

LpAmax = 0.155v + 62.8 dB(A)

R2

= 0.993

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82

10 20 30 40 50 60 70 80 90 100 110 120 130 140

v [km/h]

L p A m a x

[ d B ( A ) ]

L AE = 0.109v + 66.7 dB(A)

R2

= 0.996

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82

10 20 30 40 50 60 70 80 90 100 110 120 130 140

c) f)

Figure 2. Results of objective analyses – L AE (a), average loudness (b), average sharpness (c),LpAmax (d), percentile values of loudness N10 (e), and sharpness S10 (f).

As can be seen in Fig. 2, all the calculated stimuli characteristics, such as L AE,LpAmax, as well as loudness and sharpness, increase almost linearly with velocity. Thislinear relationship is particularly strong in the velocity range of 50 -110 km/h.

SubjectsEighteen participants took part in Experiment 1 and eleven in Experiment 2. All theparticipants from Experiment 2 also took part in Experiment 1. The participants werebetween 19 and 24 years old. All participants qualified as having normal hearing(normal hearing was defined as the audiometric threshold of 20 dB HL, or better, for the frequency range from 250 to 8000 Hz, according to the ANSI standard [6]) andwere paid for their participation.

ProcedureIn Experiment I participants judged the noise annoyance of 17 different stimuli (simu-lated car pass-bys with velocities of 30 to 110 km/h in 5 km/h steps). Each stimulus

was presented 30 times in random order. The whole experiment was carried out inthree 20-minute sessions – one session per day. Participants judged the noise an-noyance of each stimulus using an 11 point (0-10) numerical scale. The scale used in

N10 = 0.2224v + 16.85 sone

R2

= 0.999

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24

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48

10 20 30 40 50 60 70 80 90 100 110 120 130 140

v [km/h]

N 1 0 [ s o n e ]

S10 = 0.009v + 2.113 acum

R2

= 0.997

2.3

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2.6

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2.8

2.9

3.0

3.1

3.2

3.3

10 20 30 40 50 60 70 80 90 100 110 120 130 140

v [km/h]

S 1 0 [ a c u m ]

N = 0.068v + 15.5 sone

R2

= 0.991

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1819

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25

26

10 20 30 40 50 60 70 80 90 100 110 120 130 140

v [km/h]

N [ s o n e ]

S = 0.0017v + 1.859 acum

R2

= 0.979

1.88

1.90

1.92

1.94

1.96

1.98

2.00

2.02

2.04

2.06

2.08

2.10

10 20 30 40 50 60 70 80 90 100 110 120 130 140

v [km/h]

S [ a c u m ]

v [km/h]

[ d B ( A ) ]

L A E

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this study is recommended for noise surveys by ICBEN [7, 8]. The subjects weregiven the following instruction: What number from zero to ten best shows how muchyou are bothered, disturbed, or annoyed by the noise? If you are not at all annoyedchoose zero, if you are extremely annoyed choose ten, if you are somewhere in be-tween, choose a number between zero and ten.

In Experiment II minimal differences in velocity corresponding to just noticeablechanges in annoyance (velocity-annoyance JND’s) were estimated using the methodof constant stimuli. Velocity-annoyance JND’s were obtained for three reference ve-locities: 50, 90 and 110 km/h. The stimuli were presented in pairs. Each pair waspresented 30 times. Subjects were asked to judge which of the two stimuli in the pair was perceived as more annoying. The velocities of stimuli presented in pairs differ from each reference velocity in 5 km/h steps from –20 to +20 km/h.

3 Results

Experiment IThe averaged (over 18 participants) ICBEN annoyance ratings (with the 95 % confi-dence intervals), obtained for seventeen velocities (30 – 110 km/h) are presented inFig. 3.

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

20 30 40 50 60 70 80 90 100 110 120

v [km/h]

A N N

O Y A N C E

Figure 3. Results of Experiment I – annoyance ratings for the velocity range of 30-110km/h.

Within subject ANOVA showed statistically significant differences in annoyance rat-ings between different velocities (F(16,8874) = 1008,7; p <<0.05). The annoyance

ICBEN ratings linearly increase with velocity. However, for velocities below 40 andabove 105 km/h there are smaller changes in annoyance with velocity. This effectshould lead to a sigmoid shape of annoyance function if a wider velocity range hasbeen investigated. The correlation coefficients between the annoyance ratings andthe stimuli characteristics presented in Fig. 1 were all above 0.99. Thus, it was notpossible to answer which of these factors explains the perceived annoyance on thebasis of the correlation coefficient’s value.

To find the minimal differences in velocity which give statistically different annoyanceratings, Sheffe’s test was used. These pairs of velocities are shown in the first twocolumns of the Table 1. For each of these pairs of stimuli the following factors were

calculated: a difference in L AE and LpAmax, a ratio in loudness and in sharpness, and aratio in percentile (10%) loudness and in percentile (10%) sharpness. All these fac-tors are presented in Table 1.

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Table 1: Results of the analysis (Experiment I)

v1 v2 ∆v(v2-v1)

∆LAE ∆LpAmax Nratio

Sratio

N10ratio

S10ratio

km/h km/h km/h dB dB % % % %

30 45 15 1.9 2.9 4.2 0.5 13.2 6.4

35 45 10 1.3 2.0 2.6 0.5 9.1 4.340 45 5 0.6 1.0 1.6 0.2 5.4 2.0

45 55 10 1.3 1.8 3.0 0.6 7.1 3.3

50 60 10 1.2 1.9 3.2 0.8 7.6 4.3

55 65 10 1.2 1.6 3.4 0.7 8.4 4.0

60 65 5 0.6 0.7 1.7 0.3 4.6 1.3

65 70 5 0.6 1.0 1.9 0.5 4.3 2.4

70 80 10 1.1 1.4 3.4 1.1 6.7 3.5

75 85 10 1.1 1.6 3.5 1.3 6.9 3.4

80 90 10 1.1 1.5 3.7 1.1 6.7 2.5

85 90 5 0.6 0.8 1.9 0.5 4.0 0.9

90 100 10 0.9 1.3 3.7 1.0 5.7 3.495 105 10 1.1 1.8 3.4 1.2 6.9 3.0

100 105 5 0.5 0.8 1.7 0.6 3.2 1.3

105 115 10 0.9 0.9 3.6 0.7 6.0 3.0

Average 8.8 1.0 1.4 2.9 0.7 6.6 3.0

SD 2.9 0.4 0.6 0.9 0.3 2.4 1.4

The minimal change in velocity corresponding to a just noticeable change in annoy-ance (velocity-annoyance JND) – ∆v – varies from 5 to 10 km/h (the third column inTable 1). For the lowest velocity the velocity-annoyance JND is equal to 15 km/h.

To find out which of the objective parameters of stimuli (L AE

, LpAmax

, loudness andsharpness) could be potentially responsible for the obtained velocity-annoyanceJNDs, the values of the calculated differences or ratios in the objective parameterswere compared to the existing JND values in the literature.

For the seven tested velocities, ∆L AE (fourth column in Table 1) is below 1 dB (1dBcan be assumed as an JND value for the wideband noise [9]) – thus there is a verylow probability that participants could base their responses on this cue. For the majority of the velocities, ∆LpAmax is above the threshold and can be considered as apotential cue responsible for the velocity–annoyance JND. The average loudnessratio (column 6 in Table 1) is below the threshold for all velocities (the JND for loud-ness is about 6-7 % [10]). Since there is no clear and consistent data regarding JND

for sharpness, it is difficult to conclude whether the sharpness could be a sufficientcue for the annoyance judgment or not. We can only conclude that in most cases theN10 loudness could be used as a cue for the perception of changes in noise annoy-ance. This means that both LpAmax and N10 stimuli characteristics are important cuesfor the JND’s in annoyance as a result of velocity changes.

Experiment II

The results of Experiment II (individual data) are presented in the form of psychomet-ric curves in Fig. 4a-c. The panels (a), (b), (c) represent curves obtained for threereference velocities: 50, 90 and 110 km/h respectively. The stimuli were presented in

pairs. Each pair consisted of one reference stimulus (50, 90 or 110 km/h) and onetest stimulus. In Figure 4 a percentage of responses where test stimuli with a given

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velocity were judged as more annoying than the reference stimulus is plotted as afunction of the test stimulus velocity.

(a)

(b)

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25 35 45 55 65 75

v [km/h]

% r

e s p o n s e s - t e s t s t i m u l u

s

m o r e a n n o y i n g

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v [km/h]

% r

e s p o n s e s - t e s t s t i m u l u s

m o r e a n n o y i n g

(c)

0

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85 95 105 115 125 135

v [km/h]

% r e s p o n s e s - t e s t s t i m u l u s

m

o r e a n n o y i n g 1

2

3

4

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6

7

8

9

10

11

Figure 4. Results of Experiment II. Psychometric curves obtained for three reference velocities:50 (a), 90 (b) and 110 km/h (c).

Minimal differences in velocity corresponding to just noticeable changes in annoy-ance (velocity-annoyance JND’s) were estimated by fitting theoretical cumulative

probability density functions to the experimental data (presented in Fig. 4). Thethresholds ( v, corresponds to 75% of correct responses) were calculated for eachreference velocity and each participant, and are presented in Table 2.

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Table 2. Results of Experiment II.

vsubject

50km/h

90km/h

110 km/h

MG 14.4 11.9 8.2

PD 17.7 18.2 12.8KD 16.5 11.1 13.1

NW 12.4 8.5 8.8

MK1 18.3 17.3 21.4

MK2 12.8 15.0 19.2

NP. 12.5 5.5 5.9

MD 18.5 6.3 5.8

BW 12.4 10.7 11.1

MK3 14.2 8.9 9.7

AK 13.9 11.9 16.2

average 14.9 11.4 12.0

SD 2.4 4.1 5.2

Table 3. Results of Experiment II.

L AE [dB] LpAmax [dB] N10 - ratio [%] S10 - ratio [%]Subj.

50km/h

90km/h

110km/h

50Km/h

90km/h

110km/h

50km/h

90km/h

110km/h

50km/h

90km/h

110km/h

MG 2.2 1.8 1.2 3.2 2.6 1.8 11.4 9.5 6.5 5.1 4.2 2.9

PD 2.7 2.8 1.9 3.9 4.0 2.8 14.1 14.5 10.2 6.2 6.4 4.5

KD 2.5 1.7 2.0 3.6 2.4 2.9 13.1 8.8 10.4 5.8 3.9 4.6

NW 1.9 1.3 1.3 2.7 1.9 1.9 9.9 6.8 7.0 4.4 3.0 3.1

MK1 2.8 2.6 3.2 4.0 3.8 4.7 14.5 13.8 17.0 6.4 6.1 7.5

Mk2 1.9 2.3 2.9 2.8 3.3 4.2 10.2 11.9 15.3 4.5 5.3 6.7

NP. 1.9 0.8 0.9 2.7 1.2 1.3 9.9 4.4 4.7 4.4 1.9 2.1

MD 2.8 1.0 0.9 4.1 1.4 1.3 14.7 5.0 4.6 6.5 2.2 2.0

BW 1.9 1.6 1.7 2.7 2.4 2.4 9.9 8.5 8.8 4.4 3.8 3.9

MK3 2.1 1.3 1.5 3.1 2.0 2.1 11.3 7.1 7.7 5.0 3.1 3.4

AK 2.1 1.8 2.4 3.1 2.6 3.6 11.1 9.5 12.9 4.9 4.2 5.7

Av. 2.2 1.7 1.8 3.3 2.5 2.6 11.8 9.1 9.6 5.2 4.0 4.2

SD 0.4 0.6 0.8 0.5 0.9 1.1 1.9 3.3 4.1 0.9 1.5 1.8

There are no statistically significant differences between the threshold values ob-

tained for different reference velocities [F(2,30)=2,29: p>0.05]. It means the averagethreshold value is 12.8 km/h. Although the average velocity-annoyance threshold ob-tained in Experiment II is a little bit higher than that obtained in Experiment I, there isa reasonable agreement in the results obtained from both experiments. The calcula-tions of differences and ratios of objective factors suggest that L AE as well as LpAmax could be potentially used as a cues for all the tested velocities. The N10 loudness inthe majority cases exceeds the loudness JND significantly (up to over 100%) for allreference velocities.

4 Conclusions

In the present paper a linear dependence between the annoyance judged on an IC-BEN scale and the velocity of a passenger car was obtained. Experimental resultssuggests departures from this linearity at velocities below 40 km/h. Using the method

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of constant stimuli, the minimal changes in velocity corresponding to JND in annoy-ance were estimated for a passenger car, for velocity ranges of 30-110 km/h. Thevelocity-annoyance JND’s obtained in Experiment II differ across subjects. However,there are no statistically significant differences in the velocity thresholds obtained for different reference velocities. On average, the velocity threshold for three investi-

gated reference velocities 50, 90 and 110 km/h is equal to 12.8 km/h. The objectiveanalyses showed that factors related to the maximum values of loudness, (N10) ex-plain velocity-annoyance JNDs better than the calculated average values of loud-ness, N.

5 References

[1] R. Nota, R. Barelds and D. Maercke Engineering method for road traffic andrailway noise after validation and fine-tuning - Technical Report HAR32TR-040922-DGMR20 Harmonoise (2005)

[2] R. Makarewicz, and P. Kokowski, "A simplified model of ground effect." J.

Acoust. Soc. Am. 101: 372-376 (1997)[3] Acoustics- Attenuation of sound during propagation outdoors - Part 1: Calcula-

tion of the absorption of sound by the atmosphere, International Standard ISO9613-1:1993 (International Organization for Standardization, Geneva, Switzer-land, 1993)

[4] T. Kaczmarek, “Auditory perception of sound source velocity”, J. Acoust. Soc. Am. 117(5), 3149–3156 (2005).

[5] T. Kaczmarek „Road-vehicle simulation for psychoacoustic studies,” Proceed-ings of ICA 2007, Madrid, SPAIN, (2007)

[6] Specifications for Audiometers, American National Standards Institute ANSIS3.6-1996 (Acoustical Society of America, New York, 1996).

[7] J. M. Fields, R.G. De Jong, T. Gjestland, I. H. Flindell, R. F. S. Job, S. Kurra,P.Lercher, M. Vallet, T. Yano, R. Guski, U. Felscher-Suchr, R. Schumer. “Stan-dardized General-Purpose Noise Reaction Questions for Community NoiseSurveys: Research and a Recommendation.” Journal of Sound and Vibration,242(4), 641-679, 2001

[8] A. Preis, T. Kaczmarek, H. Wojciechowska, J. Żera, J. M. Fields. „Polish versionof standardized noise reaction questions for community noise surveys.” Interna-tional Journal of Occupational Medicine and Environmental Health, 16(2),155-159, (2003)

[9] B. C. J. Moore, An introduction to the psychology of hearing (Academic Press,

London, 1989)[10] B. Berglund, A. Preis and K. Rankin, “Relationship between loudness and an-noyance for ten community sounds.” Environment International, 16, 523-531,(1990)

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