Engineering Convention Paper 9755...keyboard visual mark laser spot laser pointer keypad Fig. 1: Listeners during the localisation experiments in 2012 (top) and 2017 (bottom). The

Audio Engineering Society

Convention Paper 9755Presented at the 142nd Convention2017 May 20–23, Berlin, Germany

This paper was peer-reviewed as a complete manuscript for presentation at this convention. This paper is available in the AES E-Library (http://www.aes.org/e-lib) all rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society.

Improvement of the reporting method for closed-loophuman localization experimentsFiete Winter1, Hagen Wierstorf2, and Sascha Spors1

1Institute of Communications Engineering, University of Rostock, Rostock, D-18119, Germany2Audiovisual Technology Group, Technische Universität Ilmenau, Ilmenau, D-98693, Germany

Correspondence should be addressed to Fiete Winter ([email protected])

ABSTRACT

Sound Field Synthesis reproduces a desired sound field within an extended listening area using up to hundreds ofloudspeakers. The perceptual evaluation of such methods is challenging, as many degrees of freedom have to beconsidered. Binaural Synthesis simulating the loudspeakers over headphones is an effective tool for the evaluation.A prior study has investigated, whether non-individual anechoic binaural synthesis is perceptually transparentenough to evaluate human localisation in sound field synthesis. With the used apparatus, an undershoot for lateralsound sources was observed for real loudspeakers and their binaural simulation. This paper reassesses humanlocalisation for the mentioned technique using a slightly modified setup. The results show that the localisationerror decreased and no undershoot was observed.

1 Introduction

Contrary to classical, perceptually motivated spatial re-production techniques such as stereophony, approachesfor Sound Field Synthesis (SFS) aim at the physicallyaccurate reconstruction of a desired sound field withina target region. Typically, this region is surroundedby a distribution of loudspeakers, which are driven byindividual signals such that the superposition of theemitted sound fields produces the desired sound field.Practical implementations of such techniques cause sys-tematic artefacts in the synthesized sound field that area consequence of a departure from theoretical require-ments. As the most prominent artefact, approximatingthe continuous secondary source distribution requiredby theory with a finite number of discrete loudspeak-ers may introduce spatial aliasing. In practical setups,a perfect physical reconstruction is not possible and

SFS relies on the possible masking of the mentionedartefacts by humans. Hence, it is of high interest toevaluate human perception of SFS techniques.

Compared to classical stereophony, SFS offers moreflexibility since correct reproduction is pursued withinan extended area including many different listening po-sitions. It is also compatible with various reproductiongeometries, i.e. number of loudspeakers and shape ofthe boundary. For the systematic perceptual evaluationthis is however challenging as these additional degreesof freedom have to be considered. In the past, dy-namic binaural synthesis has emerged as a useful toolto overcome these issues and efficiently evaluate hu-man localisation in SFS. Each loudspeaker is simulatedby convolving the Head-Related Impulse Responses(HRIRs) corresponding to the apparent loudspeaker po-sition with the driving signal of the loudspeaker. Thesuperposition of all loudspeakers is played back via

Winter, Wierstorf, and Spors Improvement of reporting method for human localization experiments

visual mark laser spotlaser pointer

keyboard

visual marklaser spot

laser pointer

keypad

Fig. 1: Listeners during the localisation experiments in2012 (top) and 2017 (bottom). The rooms weredark during the experiment.

headphones. The orientation of the listener’s head istracked simultaneously and the HRIRs are switchedaccordingly.

Different studies were conducted, that compared theperceived direction of a real loudspeaker and its binau-ral simulation. As long as head tracking was applied,the localisation errors were usually in the range of 1◦

to 5◦, see for example [1, 2, 3]. One reason for thevarying results for the localisation performance foundin the literature is the fact that such experiments arecritical regarding the utilised pointing method. Due tothe fact that the actual localization error can be as smallas 1◦, the error of the pointing method has to be smallerthan 1◦, which cannot be achieved with all methods[4, 1].

In a prior study of one of the authors [5], a pointingmethod similar to [3] was used. Here, the listeners

have to point with their head towards the direction ofthe auditory event, while the sound event is present.This has the advantage that the listener is directly fac-ing the source, a region in which the minimum audibleangle is the smallest [6]. If the listeners are pointingtheir nose in the direction of the source, an estimationerror of the sources at the side will occur, due to aninteraction with the human sensory-motor system. Toovercome this, a visual pointer was added, showing thelisteners where their nose is pointing [7]. To realisesuch a visual pointer a small laser pointer was mountedonto the headphones. With this setup the localisationaccuracy was around 1◦ for real as for the simulatedloudspeaker, but only if the loudspeakers where notpositioned more than 30◦ to the side. For loudspeak-ers positioned further to the side an undershoot in thereported angle occurred in both cases.

In this contribution, the former experiment of [5] isrepeated with a slightly modified apparatus. The maingoal is to compare the localisation results with theoriginal study and to possibly identify improvementscaused by distinct changes in the experimental setup.Special attentions is drawn to the reported undershootof the original study.

2 Experimental Methods

This section describes the details of the new localiza-tion experiment and the one from [5]. The aim was adirect comparison of both studies resulting in a verysimilar setup. If there were differences between bothexperiments they are highlighted in the description bythe respective years of publication, i.e 2012 for [5] and2017 for this study. Otherwise the description appliesfor both experiments. Note, that the aim in 2012 wasto compare humans’ localisation of real sound sourceswith their respective simulation via anechoic binauralsynthesis or binaural synthesis with room reflections.The focus is now shifted towards localisation in ane-choic binaural synthesis only and how the reportingmethod can be improved compared to 2012. Detailsof the experiment in 2012 targeting the binaural roomsimulation or the real loudspeakers are irrelevant forthis comparison and are hence omitted in the followingexplanations.

2.1 Apparatus

The listening test in 2012 took place in a 83m3 acous-tically damped listening room (room Calypso in the

AES 142nd Convention, Berlin, Germany, 2017 May 20–23Page 2 of 8


Telefunken building of TU Berlin). The listeners sat ona heavy rotatable chair, 1.5 m in front of a straight cur-tain. They wore open headphones (AKG K601) withan attached head tracker (Polhemus Fastrak). The headtracker had an update rate of 120 Hz, but due to furtherdata processing the effective update rate was 60 Hz.Its measured tracking accuracy is around 1◦. The lis-teners had a keyboard on their legs for entering theresponse, compare Fig. 1. In a separate room, a com-puter equipped with a multichannel sound card includ-ing D/A converters (RME Hammerfall DSP MADI)played back all sounds. The signals travelled througha head phone amplifier (Behringer Powerplay Pro-XLHA 4700) and analogue cable to the head phones in thelistening room, a distance of approximately 5 m.

The listening test in 2017 was conducted in a 86m3

acoustically damped room (Audio laboratory at the In-stitute of Communications Engineering, University ofRostock). The listeners sat on a rotatable chair andwere surrounded by a circular curtain with a radiusof approximately 1.5 m, see Fig. 2. They wore openheadphones (AKG K601) with six optical markers at-tached to it. The head tracking is achieved with anoptical tracking system using eight infra-red cameras(NaturalPoint OptiTrack). The tracking system had anupdate rate of 120 Hz. The listeners had a keypad intheir hands for entering the response, compare Fig. 1.In a separate room, a computer equipped with a stereosound card (Focusrite Scarlett 2i2, 1st Generation) wasused for audio playback. The signals travelled throughan analogue cable of approximately 6m length to thehead phones inside the listening room.

2.2 Stimuli: Dynamic Binaural Synthesis

The basic principle of binaural synthesis as a tool for dy-namically generating the necessary stimuli is illustratedin Fig. 3. The head tracker provides the horizontal ori-entation of the listener’s head which is fed into theconvolution core of the system. Based on the currenthead orientation the corresponding impulse response isselected from the HRIR dataset. The input signal whichis supposed to be emitted by the sound source is con-volved with selected impulse response in a block-wisemanner. Each block was 1024 samples long. Possiblechanges in head orientation are handled by convolvingthe current signal block separately with the old and newimpulse response and cross-fading the results within theduration of one block. The SoundScape Renderer [8]

0.15m

virtualloudspeakers

curtain (2012)

≈ 1.5 m

curtain (2017)

Fig. 2: Sketch of experimental setup and the linear ar-ray consisting of the 19 virtual sound sources(loudspeaker symbols) with a spacing of 0.15m.The eleven source positions used in the experi-ment are shaded dark.

was utilised as the convolution core. The input signalfor SoundScape Renderer was provided by Pure Data[9] which allows to root the dry source signal into differ-ent convolution instances of the SoundScape Renderer.Each instance contained the HRIRs corresponding toa specific sound source position. This means that thesystem was able to instantaneously switch between dif-ferent conditions without having to restart the playbackof the dry audio signal. All components operated at asampling frequency of 44.1kHz. More information onthe HRIR dataset and the dry source signal is given inthe following two sections.

2.2.1 Head-Related Impulse Responses

The used HRIR dataset was measured in an anechoicchamber with an artificial head and a sound sourceplaced in the horizontal plane (at height of the ears)with a distance of 3 m and an azimuth varying from0◦ to 359◦ with 1◦ resolution. Details about the mea-surement procedure and involved equipment can befound in [10]. For non-measured source directions, theHRIRs were linearly interpolated using the two nearestmeasured HRIRs. For distances smaller or larger thanthe measured 3 m the delay and the amplitude of theHRIRs were adjusted according to the speed of soundand the free-field distance attenuation, respectively.



2.2.2 Dry Source Signal

A Gaussian white noise pulse train of 100 s length wasused as the signal emitted by sound source. Each pulsehad a duration of 700 ms followed by a pause of 300 ms.The noise signals of each pulse were statistically in-dependent. A cosine-shaped fade-in/fade-out of 20 mslength was applied at the begin/end of each pulse. Thesignal was bandpass filtered with a fourth order But-terworth filter between 125 Hz and 20000 Hz. In theexperiment, the signal was played back in a loop andwas convolved with the current HRIR for binaural re-production.

2.3 Participants

11 listeners were recruited for both experiments. Theage of the participants ranged from 21 to 33 yearsfor the 2012 study and from 26 to 60 in 2017 with arespective average of 28.6 and 38 years. 4 and 2 of thelisteners had prior experience with listening tests.

2.4 Procedure

Various trials were presented successively to listenersvia the headphones using the dynamic binaural synthe-sis technique described in Sec. 2.2. The experimentcontained 11 unique conditions1 where a single soundsource emitting the source signal described in Sec. 2.2.2was simulated. The positions of the sound sources areindicated in Fig. 2. Each listener had to pass eachcondition six times leading to 66 trials in total. Theorder of presentation was randomised with respect torepetitions and condition, while the first 11 trials wheremeant for training and contained each unique conditionexactly once. In 2012, the remaining 55 trials weresplit into two sessions with 22 and 33 trials contain-ing each unique condition exactly two and three times,respectively.

The participants were instructed to determine the hori-zontal direction of the perceived auditory event, whilethe vertical position should be ignored. A pointingmethod similar to [3] was used, where the listenerswere supposed to point into the direction using thelaser pointer. The curtain served as a projection surfacefor the laser. If the listeners were sure to point intothe correct direction, they pressed a key on the input

1Due to the additional presentation techniques, i.e. binaural roomsimulation and real loudspeakers, the experiment in 2012 originallycontained 33 different conditions.

HRIRsfor head

orientation φ

convolution &HRIR switching

head trackerprovides

head orientation φ

drysource signal

simulated sound source

Fig. 3: Basic principle of dynamic binaural synthesisfor one simulated sound source.

device. The localisation result was calculated as thearithmetic mean of 10 values obtained from the headtracker. For the respective update rate, this correspondsto a time of 167 ms (2012) and 83 ms (2017). After thekey press, the next condition started instantaneously.

In an a-priori calibration phase, the listener was indi-cated to point towards a given visual mark on the cur-tain. In 2012, a small permanent mark was pasted onthe curtain. In 2017, a steady laser cross was projectedonto the curtain and switched off after the calibrationstage. The room was darkened after calibration.

3 Data Analysis

In following, the statistical methods used to evaluateand compare to the acquired data are presented.

3.1 Perceived Azimuth

As a result of each listening experiment the three-dimensional dataset φ̂ r

l (φc) describes the perceived az-imuths. The index l corresponds to one of the L listen-ers. The listening condition and respective ground truthsource azimuth are denoted by c and φc, respectively.The total number of conditions is C = 11. As eachcondition is presented R times to each listener, theserepetitions are indicated by r. It is assumed, that allsamples φ̂ r

l (φc) are statistically independent due to therandomisation of the presentation order.



3.1.1 Data Correction

It has been already discussed for the original study [5,Sec. 2.6], that the relative location of the laser pointeron the headphones might vary among the listeners (andsessions). This can be caused by e.g. undesired contact,switching on/off the pointer, or changing the batteries.Also the position of the headphones on the head is dif-ferent for each listener. Consequently, the orientationof the pointing device and the listener’s median planedo not necessarily align. This introduces a direction-independent bias to the pointing method, as the listeneris forced to point with the laser beam although his/hernose is pointing in a slightly different direction. Underthe assumption, that the localisation of each listener issymmetrical to the left and right, this bias is correctedvia

φ̃rl (φc) = φ̂

rl (φc)−

1CR

C

∑c=1

R

∑r=1

φ̂rl (φc)+

1C

C

∑c=1

φc . (1)

The second term on the right-hand side describes theaverage azimuth for the individual listener over all con-ditions and repetitions, which is ideally (unbiased case)equal to the arithmetic mean of the ground truth direc-tions φc (last term). The last term is included since themean over all ground truth angles is not zero. For the2012 experiment, the data calibration is performed foreach session individually. Hence, R = 2 and R = 3 in(1) for the first and the second session. The correcteddata of the two sessions was pooled afterwards so thatR = 5 is used for both studies in the following explana-tions. The azimuthal localisation error is finally givenas

∆rl (φc) = φ̃

rl (φc)−φc . (2)

3.1.2 Descriptive Statistics

The localisation performance of an individual listenerw.r.t. a specific condition is evaluated via the samplemean

∆̄l(φc) =1R

R

∑r=1

∆rl (φc) (3)

and the respective corrected sample standard deviation

sl(φc) =

√1

R−1

R

∑r=1

[∆r

l (φc)− ∆̄l(φc)]2. (4)

For the average performance for one condition the datais pooled w.r.t. repetitions and listeners. The samplemean is hence defined as

∆̄(φc) =1

LR

L

∑l=1

R

∑r=1

∆rl (φc) . (5)

with its respective corrected sample standard deviation

s(φc) =

√1

LR−1

L

∑l=1

R

∑r=1

[∆r

l (φc)− ∆̄(φc)]2. (6)

The overall sample mean, i.e. pooled w.r.t. repetitions,listeners, and conditions, is always zero due to thedata correction, cf. (1). The overall sample standarddeviation is hence given as

s =

√√√√ 1CLR−1

C

∑c=1

L

∑l=1

R

∑r=1

[∆r

l (φc)]2. (7)

and is equivalent to the overall root mean squared error.

3.1.3 Inductive Statistics

For the following explanations it is assumed that thesigned localisation error is approximately Gaussiandistributed. In order to judge, if the signed localisationerror for a specific condition significantly differs from0◦, the confidence interval{

µ(φc)

∣∣∣∣∣∣µ(φc)− ∆̄(φc)∣∣≤ t(1−α/2;LR−1)

sl(φc)√LR

}(8)

of the respective population mean µ(φc) is used. t(p;ν)denotes p-Quantile of the Student’s t-distribution withν degrees of freedom. A significant difference ispresent, if the confidence interval does not include 0◦.This procedure is equivalent to a two-sided one-samplet-Test with an significance level of α . The confidenceinterval for the population standard deviations σ(φc)are given as{

σ(φc)

∣∣∣∣∣√

LR−1χ2(1−α/2;LR−1)

≤ σ(φc)

s(φc)≤√

LR−1χ2(α/2;LR−1)

}(9)

with χ2 denoting the Quantile of Chi-squared distribu-tion with same parametrisation as for the t-distribution.An F-test is used to show, if the population standard



deviation for a specific condition in 2012 is signifi-cantly larger than for 2017. The null hypothesis ofequal standard deviations is rejected if

s22012(φc)

s22017(φc)

> F(1−α;LR−1;LR−1) . (10)

Rejecting the null hypothesis is equivalent to a signif-icantly higher standard deviation in 2012. F(p;ν1;ν2)

denotes the p-Quantile of the F-distribution with ν1and ν2 degrees of freedom. A analogue F-test can alsobe formulated for the overall standard deviations (7)with ν1 = ν2 =CLR−1.

3.2 Elapsed Time per Trial

In addition to the localisation error, the elapsed timeτr

l (φc) in each trial was measured. The indices r, l,and c correspond the same dimensions as described inSec. 3.1. As the focus lies on the localisation accuracy,only simple descriptive statistics such as quantiles andhistograms are used to compare both studies. Further-more, the elapsed time is strictly non-negative and itsdistribution is likely to be non-Gaussian, which is anessential assumption for the most standard statisticaltests.

4 Results and Discussion

It turned out during data analysis, that the standarddeviation of the localisation error for one listener ineach study was approximately twice as high comparedto the maximum among the other participants. Theseparticipants were excluded from the analysis resultinginto L = 10 subjects per study. The histograms for thelocalisation error are shown in Fig. 4, top row. It canbe seen, that the localisation error is approximatelyGaussian distributed and hereby fulfils the assumptionnecessary for statistical test methods. The condensedlocalisation results are given in Fig. 5: The mean signederror for each condition never exceeds 5◦ and 3◦ for2012 and 2017, respectively. As already mentionedin Sec. 1, an underestimation of the source directionstowards the centre can be observed for the lateral soundsources in 2012. In 2017, this phenomenon cannot beobserved. For almost every condition, the localisationblur indicated by the standard deviation is significantlyhigher in 2012 compared to the corresponding valuefor 2017. The overall standard deviations or root meansquared localisation errors, cf. (7), for 2012 and 2017

0

0.2

0.4

-10 0 100

0.2

0.4

-10 0 10

0

0.1

0.2

0 10 20 300

0.1

0.2

0 10 20 30

Rel

ativ

eFr

eque

ncy

localisation error / deg

2012

localisation error / deg

2017

Rel

ativ

eFr

eque

ncy

time per trial / s

2012

time per trial / s

2017

Fig. 4: The top row shows the normalised histogramsfor the localisation error ∆r

l (φc), cf. (2), of 2012(left) and 2017 (right). The time per trial τr

l (φc)is plotted in the bottom row. All histogramsare based on the pooled data over all listeners,conditions, and repetitions. The bin sizes of thehistograms are 2◦ and 1s, respectively.

are 4.8◦ and 3.1◦, respectively. The former is alsosignificantly higher than the latter (F-test, α = 5%,ν1 = ν2 =CLR−1).

The main reason for the non-observed localisation un-dershoot in the study of 2017 is most probably thecircular shape of the curtain establishing a close to ro-tationally invariant projection plane for the pointingmethod. As depicted in Fig. 1 (top), the ends of thestraight curtain in 2012 define a clearly visible limit ofprojection plane. Even in a dark room these limits areobservable due to the change of the reflection pattern ofthe laser pointer between the curtain and the adjacentwall. Being aware of these limits might have forced theparticipants to localise towards the centre of the curtain.A further reason for the decrease in localisation blurbetween 2012 and 2017 might be the increased updaterate of head tracker (see Sec. 2.4). As a constant num-ber of values have been captured from the head trackerfor averaging, the listeners had to keep their head stillfor a shorter time frame.

The histogram of the elapsed time per trial is shownin Fig. 4, bottom row: the assumption about its non-Gaussian distribution is confirmed. In can be seen, thatthe elapsed time in the 2017 reaches higher values thanin 2012. The quantiles and arithmetic means shown



in Tab. 1 also attest that the participants in 2017 had ahigher response time than in 2012. Although a compar-ison of the number of participants with prior experienceor of the average age of the participants (see Sec.2.3)immediately suggest a connection between the listenercomposition and elapsed time, no further evidence forthat could be found by the authors.

The measured data is available for 2012 under [11] andfor 2017 under [12].

5 Conclusion

In this study, an experiment to evaluate the human lo-calisation in anechoic binaural synthesis [5] has beenrerun with some important modifications of the appa-ratus. As the main difference, a circular curtain as theprojection surface for the pointing method was usedinstead of a straight curtain. Besides the rotational in-variance, this setup also allows for listening test withsound sources located 360◦ around the listener. Theanalysis of the results revealed that the localisation er-ror and localisation blur have decreased compared tothe original study which is mainly due to changes in theapparatus. Hence, it is possible to use this experimentalsetup to evaluate human localisation in Sound FieldSynthesis without the restrictions with respect to thesound source location reported of the original study.

To further improve the method, better calibration mech-anisms eliminating the bias caused by the orientationoffset between the listener’s head and the laser pointerremain as future work. These would allow to study pos-sibly existing phenomena which became unobservabledue to the data correction. A more robust mounting oflaser pointer on the headphones decreasing the impactof undesired or unavoidable contact is also beneficialfor this purpose.

As a drawback, the average time which was needed bya participant to assess one trial increased compared tothe original study. Clear reasons for this could howevernot be identified. Future research has to answer thequestion, whether the changed apparatus caused thisincrease. This is of importance for the practicabilityand scalability of the experiment.

References

[1] Seeber, B. U., Untersuchung der auditiven Lokali-sation mit einer Lichtzeigermethode, Ph.D. thesis,2003.

elapsed time 2012 2017

arithmetic mean 5.6 9.05%-quantile 2.2 2.6

median 4.6 6.895%-quantile 13.6 24.2

Table 1: Comparison of the elapsed time per trial givenin seconds.

[2] Bronkhorst, A. W., “Localization of real and vir-tual sound sources,” The Journal of the AcousticalSociety of America, 98(5), pp. 2542–53, 1995.

[3] Makous, J. C. and Middlebrooks, J. C., “Two-dimensional sound localization by human lis-teners,” The Journal of the Acoustical Societyof America, 87(5), pp. 2188–2200, 1990, doi:10.1121/1.399186.

[4] Majdak, P., Laback, B., Goupell, M., and Mi-hocic, M., “The Accuracy of Localizing VirtualSound Sources: Effects of Pointing Method andVisual Environment,” in 124th Audio EngineeringSociety Convention, p. Paper 7407, 2008.

[5] Wierstorf, H., Spors, S., and Raake, A., “Per-ception and evaluation of sound fields,” in OpenSeminar on Acoustics, Boszkowo, Poland, 2012.

[6] Mills, A. W., “On the minimum audible angle,”The Journal of the Acoustical Society of America,30(4), pp. 237–46, 1958.

[7] Lewald, J., Dörrscheidt, G. J., and Ehrenstein,W. H., “Sound localization with eccentric headposition.” Behavioural Brain Research, 108(2),pp. 105–25, 2000.

[8] Geier, M. and Spors, S., “Spatial Audio with theSoundScape Renderer,” in 27th Tonmeistertagung– VDT International Convention, Cologne, Ger-many, 2012.

[9] Puckette, M. et al., “Pure Data: another integratedcomputer music environment,” Proceedings of thesecond intercollege computer music concerts, pp.37–41, 1996.

[10] Wierstorf, H., Geier, M., and Spors, S., “A FreeDatabase of Head Related Impulse Response Mea-surements in the Horizontal Plane with Multiple



−6

0

6

2

6

10

−6

0

6

−45 −30 −15 0 15 30 45

2

6

10

−45 −30 −15 0 15 30 45

avr/

deg

arithmetic mean (avr) of signed error

2012

std

/deg

standard deviation (std) of signed error

2012

avr/

deg

φc / deg

2017

std

/deg

φc / deg

2017

Fig. 5: The top and the bottom row show the results for the studies in 2012 and 2017, respectively. The left columnshows the mean of the localisation error ∆̄(φc) for each condition, cf. (5), together with the (1−α) = 95%-confidence interval of the population mean, cf. (8). The black triangles at the bottom of each plot indicate asignificant difference (t-test, α = 5%) of the population mean from zero for the respective condition. Thesample standard deviation s(φc) for each condition, cf. (6), together with the 95%-confidence interval ofthe population standard deviation, cf. (9), are shown in the right column. The black triangles at the bottomof each plot indicate a significantly (F-test, α = 5%) higher population standard deviation in 2012 than2017 for the respective condition. The individual subject’s mean ∆̄l(φc) (left) and standard deviation sl(φc)(right) are shown in grey.

Distances,” in Proc. of 130th Aud. Eng. Soc. Conv.,London, UK, 2011.

[11] Wierstorf, H., “Localisation of a real vs. binauralsimulated point source – data,” 2016, doi:10.5281/zenodo.164616.

[12] Winter, F., Wierstorf, H., and Spors, S., “Im-provement of reporting method for closed-loophuman localization experiments – Data,” 2017,doi:10.5281/zenodo.245826.


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Engineering Convention Paper 9755...keyboard visual mark laser spot laser pointer keypad Fig. 1: Listeners during the localisation experiments in 2012 (top) and 2017 (bottom). The