VTI notat 77A 2001

VTI notat 77A-2001

Perception of some seat belt reminder sounds

Author

Sven Dahlstedt
Research division Human, Vehicle, Transport System Interaction Project number Project name Sponsor Distribution 40434 Seat Belt Reminders The Swedish National Road Administration Free

Foreword

This study was carried out as a very rapid operation, when the Swedish National Road Administration (or rather some of its officers) realised that there was an immediate need for data on how people perceive seat belt reminder signals, and also found that there was very little data available. VTI was asked to deliver some data, and we did. Because of the very narrow time limits it was not possible to delve deeper into all the subtle issues of sound perception. It was more a matter of a most basic exercise in psychophysical scaling. But next time, i.e. before the authorities and/or the industry takes the final decision on seat belt reminder sounds, I hope that we can have another opportunity to try out the optimal seat belt signal (or something close to it). In the meantime I hope that the people working with seat belt design and regulations will find some use for the data I present here. The narrow time limits put some special requirements on all the necessary arrangements, which usually had to be finished by yesterday. And I am most grateful to a lot of people, inside and outside VTI, who helped me at very short notice; particularly Christoffer Nilsson, Decibel Production, Linkping and Fredrik Borgsj, The Sound and Styling Shop, Linkping, who helped me with the production of the sounds, Hkan Wilhelmsson, VTI, who did some essential programming and Beatrice Sderstrm, VTI, who did most of the data collection.
Linkping, December 2001 Sven Dahlstedt

Contents

Summary 2.1 2.2 2.3 2.4 2.3.1 3.2 3.3 3.4 3.4.1 4.2 4.3 Background and purpose of the study Method Test sounds Sound level measurements Experimental procedure Subjects Analyses Results Just audible Loud and clear Annoying Opinions Summing up Concluding comments Methodological Criteria for seat belt reminders Further research

References

Appendix 1 Presentation of test sounds

Summary

A study was carried out to provide some background data on how acoustical seat belt reminder signals are perceived in a car. 19 subjects listened to 9 test sounds and one neutral reference sound while sitting in a stationary car and being exposed to a background noise corresponding to driving 50 km/h at top gear. Their task was to adjust the loudness level of each sound to make it just audible, loud and clear or definitely annoying. After the test session the subjects were also interviewed about which sounds they preferred or rejected. The results indicate that the more complex sounds are set at fairly uniform levels, but that two of the tested sounds were set consistently lower for the same perceived audibility. For one of these sounds the explanation to the deviation is assumed to be that the sound consisted of pure tones. For the other sound, a ticking with rather brief pulses and an instantaneous onset, the very low dB(A) values are hypothesized to be an artefact of the measurement mode. The interview gave rather conflicting results concerning the popularity of the sounds. This finding is explained by the widely differing criteria used by the subjects when preferring or rejecting a sound, which pinpoints the necessity of explicit specifications of the purpose of a seat belt reminder system

Background and purpose of the study
After it was shown that, at least in Sweden, the number of really stubborn seat belt non-users was very small (Dahlstedt, 1999) some of the seat belt promoting work has changed focus from forcing people to put it on to just reminding them. Also in the current international traffic safety work, e.g. in EEVC1 and Euro NCAP2, this direction of work seems to have been adopted. While awaiting final specifications from Working Group 16 of EEVC, Euro NCAP has taken the initiative to propose that the safety evaluation of cars shall also include the function of the seat belt reminder (henceforth abbreviated SBR) system. A proposal for how the SBRs should be assessed has been drafted by a working group of Euro NCAP (2001), and it is intended that the new criteria should take effect from the beginning of 2002. The proposal includes a great variety of aspects to be included in the evaluation of the SBR system, and in the requirements it is also stated that the sound signal should be. loud and clear under normal driving conditions. The normal driving conditions are later specified as 50 km/h in top gear on a good, asphalt road and with the ventilation fan running at of full speed. But regarding what should be considered loud and clear there is still some uncertainty. In a paper dated 18th Oct it is tentatively proposed that the sound level of the SBR signal should be at least 5 dB over the background noise in the compartment. But it was realised by the members of the working group that this figure was highly provisional, and that the whole concept of loud and clear needed some elaboration. In order to have a better basis for considerations regarding how various sound signals of different character and intensity might be perceived by ordinary, average car drivers some relevant data were needed. Therefore, VTI was asked to plan and carry out a minor study of how some existing, as well as hypothetical, SBR sounds are perceived during the prescribed normal driving conditions. In particular, the loudness levels should be established both for when a sound was just discernible as well as when it was judged as loud and clear.

Method

2.1 Test sounds
In the whole study 11 different sounds were presented. One of these was the background noise which was on during all sessions. Another was a neutral reference sound, which was presented as a SBR sound, but without any hints that it could ever be used as a reminder. The other nine were the studied reminder sounds, which are summarized in Table 1 below and also presented in somewhat more detail in Appendix 1. Originally it was planned to use two different Tick sounds one hard and one soft but after recording them it was found impossible to discriminate between them if the loudness level was kept equal. Therefore only one tick was included in the study. The background noise was recorded in a Volvo 850, 1995, during a peaceful, nightly cruise along a fairly flat and level road with a high surface standard. The road was dry, the wind speed was very low (03m/s) and the car was equipped

European Experimental Vehicle Committee European New Car Assessment Program
with a calibrated speedometer, cruise control and summer tires (Gislaved Speed 306). With the ventilation fan set at of full speed the cruise control was used to keep the speed as constant as possible at 50 kmph while the noise in the compartment was recorded. The microphone was not positioned exactly as in the draft Euro NCAP proposal, but rather close. It was approximately 10 cm to the right and 10 cm in front of the drivers right ear. The microphone was a Brel & Kjr 4165 and the recording was made on an analogue Nagra type IV-SJ. The total recording time was almost 45 minutes. During the drive some disturbances, e.g. oncoming and overtaking cars, could not be avoided. Therefore the recorded compartment noise was afterwords tested and listened to very carefully. From the total 45 min recording an interval of 6 min was finally selected to use as the background sound in the study. During these six minutes no disturbances can be heard, and the recorded sound level was within 1 dB(A) all the time. This 6 min interval was then digitized and multiplied five times to get a continuous 30 min background. No frequency analysis was carried out, but it can be assumed that this sound consists mainly of frequencies from the lower end of the audible spectrum. The neutral reference sound consisted of an excerpt from the daily meteorological observations, which can be heard three times a day on the Swedish Radio, channel 1. The voice was female and it read .Position(minor pause)Observations (noticeable pause)[Next]Position. at a very steady pace and at a fairly stable loudness level. This sound was also recorded on the analogue Nagra and later converted to a digital WAV-file. The nine actual test sounds are summed up in Table 1 and also presented in Appendix 1, but a more general description could be as follows: Tick sound (labelled A) is a real-life seat belt reminder recorded from a Volvo 244, 1985. Most people who have experienced this mechanical sound appear to consider it very efficient but not very pleasing. Chime (B), also a real-life sound, taken from a Volvo S 70, 2000. The sound is actually a synthetic copy of a true bell-chime, which is quite easily recognized. Female voice (C), a real person reading The seat belt, put on the seat belt in Swedish over and over again in a rather neutral tone and without any particular dialect. Nice triad (D), a harmonic major triad, recorded from a synthesizer but almost sounding as real bells. Unpleasant triad (E), a disharmonic triad, also recorded from a synthesizer but with the bells selected more at random. Male voice (F), another real person reading The seat belt, put on the seat belt in Swedish over and over again in a rather neutral tone and without any particular dialect. Real music (G), one bar from a rather lively melody, played on a synthetic, but rather well-sounding piano. Ringing (H), an electronic version of an electro-mechanical ringsound, almost like the old-fashioned telephone ringing. Simple music (I), the same short melody as (G), but presented in the simplest possible, digital version containing only pure tones. The real sounds A, B, C and F were recorded on the Nagra IV-SJ through a Brel & Kjr 4165 microphone. The other sounds were produced and processed digitally before anybody could listen to them.

Table 1

Label A B C D E F G H I
Summary of tested seat belt reminder sounds
Name Tick Chime Kvinn Fine Ful Man Music Ring Simple Character, description Metallic tic-tic-tic Cheap electronic copy of true bell Real female voice Harmonic triad on bells Disharmonic triad Real male voice One bar of piano music Old-fashioned telephone ring (G) melody consisting of pure tones Genuine/ Frequency synthetic (cycles/min) gen 200 syn+gen 51 gen 22 syn 35 syn 36 gen 25 syn 29 syn 25 syn 29
2.2 Sound level measurements
All sound levels were measured with a Brel & Kjr 2209 Impulse Precision Sound Level Meter equipped with a 4165 microphone, i.e. a rather reliable sound measuring device. All measurements were carried out with the conventional Afilter, thus giving sound levels adjusted for the differing sensitity for differing frequencies of the human hearing. Nevertheless, the sound measurements involved some problems mainly because of the very intermittent character of most of the sounds. According to the generally accepted specifications of IEC 60651 concerning sound meters and sound measurements, a sound can be measured with either of three time constants. In the Slow mode the time constant is 1 sec, which means that the meter calculates average sound levels over an interval (exponential time window) of 1000 ms; in Fast mode the time constant is 1/8 sec which gives floating averages over 125 ms intervals; in Impulse mode the time constant is even shorter giving averages over 35 ms intervals. Some sound meters, e.g. the B&K 2209, have an optional Peak mode, which corresponds to the highest instantaneous sound level. In the B&K 2209 the peak level is measured over an interval less than 10 microseconds. For homogeneous, continuous sounds all these measurement modes give the same result. But for more irregular sounds, a longer time constant tends to level out the measured intensity of short, or very rapidly changing, sounds. For some of the tested sounds the difference was quite substantial between these measurement modes, as can be seen in Table 2. Unfortunately, the human perception of loudness is influenced in many complex ways by the temporal characteristics of a sound, such as rise and fall time, duration, repetition and also the qualities of the masking (background) noise (see e.g. Scharf and Houtsma (1986) for an overview). This complexity makes it difficult to select a time constant for the measurements, which gives the best correspondance with the human loudness perception and unfortunately there is no ready-made filter similar to the Afilter for pitch. Since it could not be decided what measure that was most true, all four measures were taken for all the test sounds and the Fast value was taken as the default. The differences between the measurement modes are presented for all the test sounds in Table 2. The figures in the table can be used to get an impression of the peaked character of a sound by noting the total difference between Slow and Peak.

8 VTI notat 77A-2001

Table 2 Differences in sound level readings (dB(A)) depending upon the setting of the sound meter in Slow, Fast, Impulse and Peak mode, respectively, for the loudest part of the nine test sounds.
Sound A Tick B Chime C Kvinn D Fin E Ful F Man G Music H Ring I Simple Meter setting Slow 0,5 -0,9 -3,5 -1,5 -1,7 -3,1 -2,5 -1,2 -1,2 Fast Ref ref ref ref ref ref ref ref ref Impuls 5,9 0,5 3,2 0,8 0,8 2,5 1,5 0,9 1,1 Peak 20,5 3,1 13,5 10,5 9,7 13,5 12,1 11,2 13.5
The sound measurements were only made before and after the experimental session as a calibration of the computerized amplifier. During the tests only the digital readings corresponding to certain settings of the amplifier system were recorded. The digital settings had been calibrated as follows; with the microphone in a position according to the Euro NCAP proposal (between driver and passenger, 635 mm above drivers H-point) sound levels were recorded for 1215 settings over the whole range produced by the computer. For each sound the deflections of the meter were checked for at least 30 sec and the highest observed value was recorded. This was done for all four measurement modes. The sound levels were then plotted against the digital settings and straight lines fitted, giving equations describing the relations between numerical values and sound levels.
2.3 Experimental procedure
All tests were carried out indoors in a stationary car with all doors and windows closed. For this study the car had been equipped with a self-calibrating Hifi system (Pioneer DEH-P945R), thus ascertaining that the output from it should be as close to the original sound as possible. This system was used to present the prerecorded in-car background noise at a constant level of 60 dB(A). (Without this played-back sound the true background noise in the car was below 35 dB(A)). The in-car noise had been digitized and was stored on a CD, which was played on the Pioneer system. The test sounds, also digitized, were stored on the hard disc of a PC and were played back through fairly cheap, conventional PC speakers (Manufactured by JUSTer Co, sound characteristics unknown) positioned on the dashboard one speaker straight ahead and one speaker about 30 to the right. After a brief introduction, when the subject was told that the study concerned subjective experience of the loudness of actual and hypothetical seat belt reminder sounds, the subject was seated in the driver's seat of the stationary car. All experimental sessions included the same tasks in the same order, but with the presentation of the sounds randomized within each task. The first task was named Faint sounds, falling in which the subject was told to reduce the level of a presented, reasonably audible, sound until it was Just audible without extreme listening efforts. When the subject had finished the adjustment of the loudness a sign was given to the experimenter, who recorded the digital loudness setting.

There was no hurry or time limit but most subjects made their adjustments quite quickly without much hesitation. The task always started and ended with the reference sound V, and with the SBR sounds in random order in between. The second task was named Loud, rising-falling. In this task a sound was started at a barely audible level and the subject was asked to increase its loudness, until it was Loud and clear, and then signal the experimenter. The experimenter noted the loudness setting and the subject continued to increase the sound until it was experienced as definitely Annoying. After a signal to the experimenter to record the setting, the subject then reduced the sound back to Loud and clear. When this level also had been recorded, the next sound was presented, and so on. The setting of Annoyance levels was introduced to get a rather high, and individually adjusted, starting point for each descending setting. Although not included in the purpose, and not related to work of Euro NCAP, the obtained data are nevertheless presented for those who might be interested in the range of an upper acceptance limit. The third task was Faint, rising. Now each sound was started at a non audible level, so the subject was given a hand signal to start the listening and increase the sound until it was Just audible, when the set level was recorded. Just as in the other tasks the first and last sound was the V reference, with the test sounds in random order in between. After the listening tasks the session was ended with a brief interview. The subject was asked Which of these sounds that you have listened to, do you think is the best seat belt reminder, i.e. which would you prefer in your own car? Then the subject was asked to name the second best, and also the third best. Then the subject was told From the opposite point of view, which of these sounds did you find the worst, i.e. the one you preferred the least? After that the subject was also asked about the second and third worst, respectively. A complete session lasted about 45 minutes for most subjects, and in no case more than one hour. When a session was finished the subject was thanked, praised for his/her endurance and given a bonus check corresponding to 100 SEK, to buy some sweets or other consolation.

2.4 Subjects

All subjects but three were recruited from within VTI, mainly from the administrative staff. The other three were just acquaintances without any known biases towards seat belts or road safety in general. Any special prejudices concerning seat belt reminders were not checked. The only exclusion criterion was that such persons who were aware of any hearing defects or hearing problems were not permitted to take part, but no real hearing tests were carried out. One subject remembered after having finished the full test session that she had had numerous ear infections as a child. Her results were checked particularly carefully, and although indicating a certain bias compared to the group average the results were not so extreme as to motivate exclusion. The median age of the subjects was 43 years, and the full range extended from 21 to 56 years. Nine of the subjects were male, and ten female, making 19 subjects in all.

2.5 Analyses

All the recorded loudness settings were entered into Excel worksheets and converted to sound levels in dB(A) according to the equations mentioned in the end of section 2.2 above. All subsequent calculations were then made on the dB(A) figures. As descriptive summaries of the results conventional arithmetic means and standard deviations were calculated. Since the purpose of the study primarily was to collect a set of references, rather than to test whether one sound was better or worse, no tests of statistical significances were carried out.

Results

3.1 Just audible
This task, setting the loudness of the SBR sound to be Just audible against the background noise, was carried out twice by each subject; once descending from a clearly audible level and once ascending from a non audible level. The results are summed up in Table 3. Table 3 Just audible levels of SBR sounds and the reference sound V in dB(A) based on 19 subjects loudness settings in one falling and one rising series.
Sound Average sound level (fast) 38,0 48,9 48,0 47,1 46,8 45,0 47,6 43,7 35,8 48,1 Standard deviation Mean abs. difference between 2,8 5,6 3,9 5,4 4,4 4,5 4,0 6,2 4,5 7,8 Range lowest/highest subject 7,7 9,0 10,8 10,7 12,3 10,0 11,6 10,4 12,5 9,8
A Tic B Chime C Kvinn D Fin E Ful F Man G Music H Ring I Simple V Reference
3,8 5,5 5,4 6,2 7,1 6,3 6,2 6,4 5,9 5,7
The averages and standard deviations were calculated over both the falling and rising results over all the 19 subjects, thus giving the conventional description of the distribution of data. The column Mean absolute difference between falling and rising presents the average absolute difference between the result from the falling series minus the result from the rising series, thus giving an indication about the influence of the presentation context. The rightmost column gives similarly an indication of the effects of differing listening capacities and strategies by showing the difference between those subjects having the highest and lowest average loudness setting for each sound. As can be seen the average levels of the various sounds were set at a fairly constant level, with the exception of sounds A and I; the effect of increasing or decreasing the sound level gave a difference of around 5 dB(A); the difference between best and worst hearing and/or judgement strategy produced loudness differences of about 10 dB(A).

VTI notat 77A-2001 11

60,0 50,0 40,0 dB(A) 30,0 20,0 10,0 0,0 a-Tic b c d e f g h i V Sound
Figure 1 Average loudness settings of nine Just audible seat belt reminder sounds and the reference sound V for 19 subjects. The variability is indicated by the vertical lines which show the range between the subjects making the highest and lowest mean loudness settings. Some of these results are summed up in figure 1, in which the average sound levels are indicated by the fat dots and where also the uncertainty range due to subjective factors is shown as a solid line from the lowest to the highest individual mean loudness setting for each sound. As can be seen the average subject could hear all the complex sounds at levels around 15 dB(A) below the 60 dB(A) background noise. The pure-tone sound I and the peaked amplitude" sound A were heard already at more than 20 dB(A) below the background noise, but it must be kept in mind that the result for the A-sound might partly be an artefact of the mode of measurement (cf section 2.2 above). It is also rather evident that the different sensitivities and/or listening strategies of the various subjects result in a subjective uncertainty range of around 10 dB(A).

3.2 Loud and clear

The results of the subjects second task, setting the loudness of each sound so as to make it Loud and clear, are presented in table 4 and summed up in figure 2. Also in this task the subjects made the settings twice, the first time increasing the sound level and the second time decreasing it. Variability due to this presentation effect is indicated in the column Difference down/up, and variability due to individual differences is indicated in the column Range lowest/highest subject.
Table 4 Loud and clear levels of SBR sounds and the reference sound V in dB(A) based on 19 subjects loudness settings in one falling and one rising series. Average sound level 54,0 71,9 65,6 65,7 68,0 63,6 65,6 68,9 57,7 66,8 Standard deviation 5,1 3,3 4,2 4,7 4,4 4,1 5,8 3,9 4,6 4,2 Mean abs. difference between 6,7 2,1 6,7 3,8 5,0 5,7 4,4 4,5 2,6 8,6 Range lowest/highest subject 16,1 10,1 14,1 14,1 16,3 12,0 16,9 11,6 16,1 12,0
Sound A Tic B Chime C Kvinn D Fin E Ful F Man G Music H Ring I Simple V Reference
The overall relationships between the various sounds are fairly similar to the results from the task Just audible, but with a general increase of the loudness settings to a level above the 60 dB(A) background noise. This should also be evident from the summary results in figure 2 below. As can be seen it takes a sound level of 6570 dB(A) for any of the complex sounds (all except A and I) to be considered Loud and clear against the 60 dB(A) background. Regarding the I sound, which consisted of pure tones, it is not surprising that it contrasts well against the background already at a fairly low level. And regarding the ticking A sound it must again be pointed out that it is doubtful whether the Fast measurement mode gives the best correspondence to human hearing for this type of sound. If the Peak measure was chosen as more representative for this sound, then the Loud and clear-level of the A sound would be around 74 dB(A).

40,0 20,0 0,0

Figure 2 Average loudness settings of nine Loud and clear seat belt reminder sounds and the reference sound V for 19 subjects. The variability is indicated by the vertical lines which show the range between those subjects making the highest and lowest mean loudness settings.

3.3 Annoying

The third task of the subjects was to set the level of each sound so that it was experienced as definitely Annoying. This setting was done only once, and in a context which corresponds with an ascending series. Therefore these results are probably underestimates compared to results obtained as means from one rising and one falling series. And as a consequence, there are no data on context effects in table 5, where the results on Annoying sound levels are presented as in tables 3 and 4. A graphical summing up is also presented in figure 3. As can be seen the relations between the various sounds are still very similar to the results for Just audible and Loud and clear, but the overall level has increased another 1015 dB(A). It might be worth pointing out that the variability has increased, both expressed as standard deviations and ranges from highest to lowest subject. This can partly be an effect of halving the number of observations, but is certainly also an effect of the more psychological dimensions of the sounds. On lower levels it was mainly a matter of signal-to-noise ratio, but on the annoyance level other qualitative aspects, e.g. pleasantness, seemed to become important.

Table 5 Annoying levels of SBR sounds and the reference sound V in dB(A) based on 19 subjects single peak settings for each sound.
Sound A Tic B Chime C Kvinn D Fin E Ful F Man G Music H Ring I Simple V Reference Average sound level 68,1 82,2 80,2 78,4 82,1 77,7 80,5 81,8 71,1 81,5 Standard deviation 9,8 7,9 8,1 8,3 8,3 8,4 9,6 8,0 10,2 7,9 Range lowest/highest Subject 27,4 26,1 26,2 28,6 24,8 26,8 26,6 27,9 30,9 22,3

,0 ,,0

A -Tic
Figure 3 Average loudness settings of nine Annoying seat belt reminder sounds and the reference sound V for 19 subjects. The variability is indicated by the vertical lines which show the range between the subjects making the highest and lowest loudness settings.

3.4 Opinions

Every experimental session was ended with a few questions regarding the subjects opinions about the SBR sounds. The results of this little survey are summarized in figure 4 below. That sound, which a subject preferred3 the most, was given a score of +3 and the second and third choices were scored +2 and +1. But to permit expressions
Unfortunately, preference can be based on widely differing criteria, which was realised a little too late!
also of dislikes, the sound which a subject preferred the least was scored -3, and the second and third least preferred -2 and -1, respectively. The resulting scores are presented as striped bars in figure 4. There it can be seen e.g. that for the sounds A, B and G the positive and negative opinions almost cancelled each other giving total scores close to 0 (nil, zero). The two leftmost bars of each three-group show the number of subjects preferring (upwards) or rejecting (downwards) a sound. As can be seen the opinions differed so much among the subjects that none of the sounds was preferred or rejected consistently by all the 19 persons. One explanation to this result is probably the widely differing criteria which the subjects employed. This effect is discussed further in section 4.2 below.
Figure 4 Number of subjects preferring or rejecting the nine SBR sounds and the resultingnet preference scores from 19 subjects. (Left, dark bar = Number of preferring subjects; Middle, light bar = Number of rejecting subjects; Right, striped bar = Net total score, theoretical max.:57) Fortunately, the purpose of this study was not to find an optimal seat belt reminder, but rather to furnish some examples of how some sounds are perceived in a car driving environment. It should perhaps be pointed out that the presentation of popularity in figure 4 is somewhat simplified in order to make it interpretable. Some attempts were made to include also the intensity of opinion, i.e. whether a preference/rejection was the first or third choice, in the graph. In the end it was decided that such further demonstration of the complexities of SBR made the presentation itself unnecessarily complex.

4.3 Further research

The presented results cannot solve many of those problems involved in the specification of what should be required of good seat belt reminders. In fact, this study might rise more questions than it answers, but at least it highlights some
important issues that should be considered before the final decision about requirements upon a perfect-good-acceptable seat belt reminder. Considering both the anticipated effects of a good seat belt reminder, and the advantages of sound arguments from all concerned (authorities, manufacturers and users) it could be worthwhile investing in a somewhat more comprehensive project than the present. With somewhat more economical resources and a lot more time available it should be possible to collect some really useful data on SBR sounds. Ideally such a study could be similar to the project on warning signals in civil aircraft carried out by Patterson and colleagues in Cambridge (Patterson, 1989). But on the other hand, they could work towards a rather unidimensional criterion aural effectiveness. In the field of car safety it seems necessary to find a compromise between, on the one hand, a sound which forces drivers and passengers to put on the belt, and on the other, a sound which does not frighten potential buyers. That compromise ought to be a better compromise if there were more data available on e.g. - which frequencies that are easiest to hear under various driving conditions, - what sound qualities that give positive or negative associations to a sound. But first, perhaps it should be established if an acoustical signal has any effect at all on seat belt use.
Dahlstedt, Sven: (1999) Non-users motives for not wearing the seat belt. AAAM 43rd Ann. Conf., 20-22 Sept 1999, Barcelona, Spain. Euro NCAP: (2001) Belt Reminder Assessment Protocol. Draft proposal for the TWG meeting, prepared by Anders Lie, Swedish Road Administration 2001-1118. Patterson, R.D: (1989) Guidelines for the design of auditory warning sounds. Proc. Inst of Acoustics, Vol 11, part 5, pp17-24. Scharf, B. and Houtsma, A.J.M.: (1986) Audition II Loudness, pitch, localisation, aural distortion and pathology. Ch 15 in Boff, K.R., Kaufman, L. and Thomas, J.P.; Handbook of Perception and Human Performance. John Wiley, New York 1986.

Appendix 1 p 1 (6)

Sound presentation
For each of the tested sounds the distribution of sound pressure over a complete cycle is shown, with the exception of sound A, where 8 cycles are shown. The graphs give some indications of the peakedness of each sound, which is also indicated by the different readings that are obtained with different time settings on the sound level meter. These readings are presented in the text below each graph.

A_Tick

Eight old-fashioned Ticks produced electro-mechanically at a rate of about 200 ticks per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to
. Slow (1000 ms) by adding 0,5 dB(A). Impulse (35 ms) by adding 5,9 dB(A). Peak (310 s) by adding 20,5 dB(A)

Appendix 1 p 2 (6)

B_Chime
One Chime tone produced electronically at a rate of 51 such doiinnggs per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125 ms) to . Slow (1000 ms) by subtracting 0,9 dB(A). Impulse (35 ms) by adding 0,5 dB(A). Peak (3-10 s) by adding 3,1 dB(A)

C_Kvin

Female human voice saying Bilbltet, ta p bilbltet (The seat belt, put on the seat belt) 22 times per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 3,5 dB(A). Impulse (35 ms) by adding 3,2 dB(A). Peak (3-10 s) by adding 13,5 dB(A)

Appendix 1 p 3 (6)

A harmonic major triad, 35 such ding-ding-dong cycles per minute Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 1,5 dB(A). Impulse (35 ms) by adding 0,8 dB(A). Peak (3-10 s) by adding 10,5 dB(A)
A disharmonic triad, 36 such plong-plong-plong cycles per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 1,7 dB(A). Impulse (35 ms) by adding 0,8 dB(A). Peak (3-10 sek) by adding 9,7 dB(A)

Appendix 1 p 4 (6)

Male human voice saying Bilbltet, ta p bilbltet (The seat belt, put on the seat belt) 25 times per minute.
Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 3,1 dB(A). Impulse (35 ms) by adding 2,5 dB(A). Peak (3-10 s) by adding 13,5 dB(A)

G_Musik

One bar of a simple melody (same as I_Simple) presented from a fairly well sounding piano, 29 such cycles per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 2,5 dB(A). Impulse (35 ms) by adding 1,5 dB(A). Peak (3-10 s) by adding 12,1 dB(A)

Appendix 1 p 5 (6)

H_Ring
One RRRiinggg produced electronically at a rate of 25 such ringings per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 1,2 dB(A). Impulse (35 ms) by adding 0,9 dB(A). Peak (3-10 s) by adding 11,2 dB(A)

I_Simple

One bar of a simple melody (same as G_Music) made up of practically pure tones, 29 such cycles per minute. Sound level measures: dB(A) figures presented in the paper can be approximately transformed from Fast (125ms) to . Slow (1000 ms) by subtracting 1,2 dB(A). Impulse (35 ms) by adding 1,1 dB(A). Peak (3-10 s) by adding 13,5 dB(A)

Appendix 1 p 6 (6)

Reference sound, V_vaeder
12 sec excerpt from the complete file Female voice reading: Skagen.(observations).Nordkoster.(observations)Vderarna.(observations) Msskr.(observations).Trubaduren.(observations)

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PHILIPS

S24.7942-010
CD-changer cable 5m for all Philips devices, 8-pole DIN to 10-pole ISO.

S26.7912-005

Radio mounting frame for Philips radios. 50mm depth. With plastic spacer and two release keys.

S26.7912-006

Radio mounting frame for Philips radios. 50mm depth.

POWER CORDS

S20.7945-010

PIONEER

Adapter cable to connect a Pioneer radio, models DEH: 534R/535R/635R/W - P443R- P544R - P545R - P625UC P645R/W - P725UC - P725R - P735R - P735UC - P813ES - P815R - P825R - P820RDS - P835R - P875R - P945R -P8000R - P8100R - P8400MP - P9000R - P9100R - P9300R - P9400MP - DEXP: 77R - 88R - 99R - 820R - FH-P4000/6600R - KEHP: 6400R - 6800R 6900R - 7400R - 7600R - 7900R - 8200RDS - 8400R -8600R-W - 8600RDS - 8800R-V - 8900RW - 9200RDS - 9700R-W - KEXP: 8200RDS - MEHP: 7100R - 7300R - 9000R - 9100R.

S20.7945-005

Adapter cable to connect a Pioneer radio, models
DEH: 670SDK - KEH: 2000 - 2500 5300(SDK) - 5400RDS - M2000 M2500 - M3500 - M4000 - M4500 M6500 - M7200 - M7250 - M7300 M7400RDS.

S20.7945-015

Adapter cable to connect a Pioneer radio, models DEH:
2000/30R - 2100/30R - 3100/30R P3000R - P3100/10 - 4000R-B 4100R - DEX: 2000R - KEHP: 8010R - 8015.

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All products also available in bulk package; simply add a B to the article number.

S20.7945-020

Adapter cable to connect a Pioneer radio, models KEH:
1100/50 - 1200 - 1300(K/SDK) - 1311 - 1400 - 1450 - 1500/30 - 1700/30 1800R - 1900/30R - 1940R - 2100R 2300R - 2400R - 2700/30R 5700/30R - KEHP: 2800R - 3400 3700/30R - 4300R - 4400R - 4500R 4530R - 4700R - 4730R - 5700R.

S20.7945-025

Adapter cable to connect a Pioneer radio, models KEHP:
6020R/RB - 7020R - 7025R - DEH: 1300/10R - 1330 - 1400R - 1430RB 2300/30R - 2330R-B - 2430/60R 3300/30R - 3400R - DEHP: 3300/30R - 4300R-B - 4400R/RB - 6300R 6400R - 7300R - 7400MP.

S20.7945-035

Adapter cable to connect a Pioneer radio, models DEH: 5200 - 5202 - 5800 - - 8500RDS - DEHM: RDS - DSP - 77 - 940 - 970 - 980 KEHM: RDS.

S20.7945-040

Adapter cable to connect a Pioneer radio, models DEH: 2000 - 2030 - 2100 - - 3100 - 3130 - 2330RB DEHP: 3000 - 3110 - 4100R 4300RB - KEHP: 80210 8015R.

S20.7945-045

Adapter cable to connect a Pioneer radio, models KEH: 2500R - 2530R - KEHP: 3600R - 3630R - 4010 - 4011 - 4600R 4610R - 4630R - 5010R 6010R.

S20.7945-050

Adapter cable to connect a Pioneer radio, models DEHP: 5100R/RB - 6000R - 6100R 7000R(-W) - 7100R-W.

S20.7945-055

Adapter cable to connect a Pioneer radio, models DEH: 344R - 345R - 425R - 435R 524R - 525R - 624R - 625R.

S20.7945-060

Adapter cable to connect a Pioneer radio, models DEHM: 77 - 940
- 970 - 980(RDS/DSP) - 990RDS/DSP - DEHP: 705RDS - 715RDS - KEH: 5200RDS - 5202RDS - 5800RDS KEHM: 8000 - 8300 - 8500 - - 9500 - 9300RDS - 9500RDS KEHP: 6000RDS - 7000RDS.

S20.7945-065

Adapter cable to connect a Pioneer radio, models KEH: 415 - 2600(SDK) - 3600(SDK) KEHP: 11R - 4000 - 5000.

S20.7945-070

Adapter cable to connect a Pioneer radio, models KEHP: 1010/13R - 1032/33 - 2030/33R - 4020/23R.

S20.7945-075

Adapter cable to connect a Pioneer radio, models DEHP:
1590R - 2500R/RB - 2530R - 2600R 3500/90MP - 3600MPB - 3600/30MP 4500MP - 5500/30MP - 5600/30MP 5700MP - 5800MP - 6500MP - 6700MP - 7500MP - 7700MP - DEH: 1500/30R 1600R/RB - 1630R - 1700/30R - 2700R - 3700/30MP - 4700MP/B.

S20.7945-080

Adapter cable to connect a Pioneer radio, models ANHP9R/BK/10MP.

S20.7945-085

Adapter cable to connect a Pioneer radio, model AVIC-D3.

S24.7945-005

CD-changer cable 4,5m for all Pioneer P-series devices.

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INTERFACES

S22.7945-005

Aux-input interface with stereo RCA connectors for Pioneer units.

S22.7945-010

Aux-input interface with a stereo 3,5mm mini-jack connector for Pioneer units.

S857923

iPod cable to Pioneer radios with P-bus connection. With battery charging function.

S26.7945-005

Radio mounting frame for Pioneer radios.

S27.7950-005

Release keys for Pioneer radios.

S20.7954-010

Adapter cable to connect a Sony radio, models CDX: 600DSP
- 5070RDS - 5100RDS - 5290RDS 5470RDS - C90RDS - C490RDS MDXC: 150RDS - XR: 3310 - 3501 XR-RDS: 4740 - 4750 - 5520 - - 6450 - 6650 - 6750 - XRC: 200 - 210(MK2) - 410 - XRC-RDS: - 450 - 510 - 540 - 550 - 620 - 720.

S20.7954-015

Adapter cable to connect a Sony radio, all models with 13-pin connectors.

S20.7954-005

Adapter cable to connect a Sony radio, models CDX: 2500R - 3000/02 - 3100/60 - 3180R - 3250 - 4000R-RV - 4100/60 4180R(-W) - 4250R - MP30/40 - MP70/80 - CDXC: 560/580R - 580R-V - 610R-V - 650X-V - 760/80R-V - 810R-V(W) - 860R-V(W) - 860/880R 910R-V(W) - 3150R - 3180R - 4180R(W) - 4270R - 4850R - 5000R-RV - 5850R - 6850R - 7850R - 8000RX - 8850R - CDX-CA: 600X - 650R/X/V - 650/680 - 680/700X - 750(R/X) - 850R/MP - 900 - CDX-F: 5500/5550 - 7700 - 7500 - 7700 - 7750(S) - CDX-L: 280-350 - 380-400 - 410-420 480X - 450-550 - 550X/V - 580X - 600X - CDX-M:610/630R - 670/700R - 730/770R - 800 - 850MP - 1000TF - 7850 - 8800/9900 - CDX-R: 3000/3300 - 3350/6750 - CDX-S: 470RDS - 2000/2050 - 2250(S) - MDXC: 150R - 670/770R - 5970R - 6500R - 790RDS - 7970R - 8900/70R MEX: 5DI - WX-C: 570R - XR: 1300R - 1800R - 2200 - 3501MK2 - 3690/3700 - 4800/80R - 6600 - 6690/6700 - XRC: 100/101 - 110/111 - - 290RDS - 300RDS - 500RDS - 650RDS - 700 - 750RDS - 850RDS - 900RDS - 2300R - 6210R - 6220R - 7200R - 7220R - 7500R-RX 8100R - 8220R - 9100R - XR-CA: 200/300 - 370/670X - 400/600 - 600X/V - 800 - XR-L: 200/240 - XR-M: 500/510R - XCC: 200.

S20.7954-020

Adapter cable to connect a Sony radio, model MEX-1HD.

CD CHANGER ADAPTER LEADS

S24.7954-005
CD-changer cable 4,5m for all Sony Unilink devices.

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