# Exploring Individualization of Sound Stimuli

Salomé Sudre, Sølvi Ystad, Richard Kronland-Martinet, Laetitia Petit, Mitsuko Aramaki

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Salomé Sudre, Sølvi Ystad, Richard Kronland-Martinet, Laetitia Petit, Mitsuko Aramaki. Exploring Individualization of Sound Stimuli. 17th International Symposium on Computer Music Multidisciplinary Research, Nov 2025, London, United Kingdom. 10.5281/zenodo.17497303. hal-05372282

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# Exploring individualization of sound stimuli

Salomé Sudre<fnref n="1" />,<fnref n="2" />[0009-0005-5514-8912], Sølvi Ystad<fnref n="2" />[0000-0001-9022-9690], Richard Kronland-Martinet<fnref n="2" />[0000-0002-7325-4920], Laetitia Petit<fnref n="1" />[0000-0003-3501-2952], and Mitsuko Aramaki<fnref n="2" />[0000-0001-6518-374X]

**Abstract.** There is extensive literature on the effects of binaural beats on cognitive states, however, the findings are often contradictory. This inconsistency may be due to the use of fixed, high-pitched frequencies in experimental protocols, which can make the sounds unpleasant to listen to. The aim of this article is to explore the individualization of spatialized sounds. To do so, participants were asked to create a sound of their choice by selecting both the fundamental and beat frequencies. We examined different types of sounds, including monaural and binaural beats, panning beats, and alternate beeps. The results reveal individual variability in the perception and preference of sounds, although some general trends emerged, such as a preference for low frequencies. Each type of sound evoked specific imagery, ranging from mechanical objects to atmospheric scenes, highlighting the importance of emotional and symbolic dimensions in studies of human auditory perception. In conclusion, these preliminary findings support the idea that, in the absence of universal rules regarding sound preference and perception, an individualized approach could offer deeper insight into the effects of binaural beats on cognitive states.

**Keywords:** Spatialized sound · Perception · Individualized sound.

## 1 Introduction

This paper presents an ongoing exploratory study on the individualization of sound stimuli in the context of their influence on the mental state of the listener. For that purpose, we investigated in a previous study the phenomenon of binaural beats (BB) that arises when two pure tones with slightly different frequencies are presented separately into each ear [14]. The listener perceives a third sound,

<figure><img src="image_2.png" /></figure>

All rights remain with the authors under the Creative Commons Attribution 4.0 International License (CC BY 4.0).

Proc. of the 17th Int. Symposium on Computer Music Multidisciplinary Research, London, United Kingdom, 2025

<footnote n="1">¹ Aix Marseille Univ, LPCPP (Laboratoire de Psychologie Clinique, de Psychopathologie et de Psychanalyse) (EA 3278), 13621 Aix-en-Provence, France</footnote>

<footnote n="2">² Aix Marseille Univ, CNRS, PRISM (Perception, Representations, Image, Sound, Music), 31 Chemin J. Aiguier, 13402 Marseille Cedex 20, France

sudre@prism.cnrs.fr</footnote>
characterized by a carrier frequency that is the average of the two tones, and a
modulation frequency corresponding to the difference between them. BB have
been proposed as a means of influencing the mental and cognitive state of the
listener, by modulating electrical brain activity (for a review, see [6,1,2,8]).

From an acoustic perspective, it can be shown that these beats are equivalent
to the movement of a virtual sound source around the listener. In our previous
study, we highlighted similar effects between these two types of auditory stimu-
lation (BB and the sounds evoking movement of a virtual sound source). These
stimuli, presented discretely or continuously, with a carrier frequency of 440 Hz
and beat frequencies of 6 or 40 Hz, promoted an improved state of relaxation,
associated with changes in brain electrical activity measured by EEG, compared
to non-spatialized auditory stimulation (monaural beats, [14]).

Numerous studies have investigated the effects of binaural beats on atten-
tion, but the findings remain inconclusive. Although some report improvements
in alertness and attention performance [3,9,13], others have not been able to
replicate these effects [14,10,4], and no consensus has emerged. We believe that
this disparity of findings could be due to the use of stimuli constructed with fixed
frequencies and identical for all participants. In line with these considerations,
studies showed that when participants are asked to produce a regular rhythm at
a pace that suits them, they tend to produce a tempo averaging around 120 bpm
(i.e. 500 ms, [12]). However, this phenomenon, known as *preferred tempo*, varies
between individuals [7,11,12]. It also was shown that people prefer to listen to
rhythms that match their preferred tempo [11].

The current paper therefore presents a study allowing participants to con-
struct their own sounds by adjusting the auditory parameters (frequency and
beat values) themselves. Our main hypothesis is that within the studied pop-
ulation, there is a tendency toward specific auditory attributes, though with
interesting variability reflecting individual specificity. In the longer term, our
hypothesis is that by adapting sound stimuli to each participant, the observed
effects of auditory stimuli on emotional and cognitive states would be enhanced.

2 Materials and Methods

## 2.1 Participants

Sixteen participants (5 females, 11 males), with ages ranging from 20 to 36 years (M = 25.1, SD = 4) took part in the experiment. The participation criteria were the following: normal or corrected vision and hearing, no neurological history. Written informed consent was obtained from all participants involved in the study, which was reviewed and approved by the ethics committee of Aix-Marseille University. Participants were informed that they were free to leave the experiment at any time and that their data would be treated anonymously.
## 2.2 Stimuli

The four types of stimuli used in our previous study [14] were investigated. In particular, the participants were asked to construct the following four stimuli by acting on specific auditory parameters:

- Monaural beats (no spatial attributes): the generated sound is a pure tone of fundamental frequency $f_0$ and modulated in amplitude by a cosine function of frequency $f_b$ defined as ‘beating frequency’. The resulting sound is presented simultaneously to both ears.

- Binaural beats (BB): two pure tones of different frequencies presented separately in each ear. The frequency $f_0$ corresponds to the average of the frequencies of the two pure tones, while the beating frequency $f_b$ is equal to the difference between them.

- Panning beats: a pure tone of fundamental frequency $f_0$ is modulated in amplitude by a specific panning law which is a sine function of frequency $f_b$ in the left ear and a cosine function of frequency $f_b$ in the right ear.

- Alternate beeps: a sequence of beeps presented alternately in each ear at frequency rate $f_b$. A single beep is 80 Hz amplitude-modulated pure tone of fundamental frequency $f_0$.

For each type of stimuli, the participants could modify 2 parameters, i.e. the fundamental frequency $f_0$ and the beating frequency $f_b$, to construct their own sounds, as detailed in the next section.

## 2.3 Procedure

For each type of stimuli (experimental conditions), participants were asked to construct a sound by choosing, on a graphical interface, the value of the fundamental frequency (between 20-1000 Hz) and the beat frequency (between 0-40 Hz). A ‘Gain’ slider was also proposed to the participants to adjust the intensity of the sound only if they cannot hear the sound in a comfortable way. The only instruction given to the participants was: ‘Create the sound of your choice’. The choice of instructions was validated by a pilot study conducted before this experiment. If participants asked for more information, they were told that they could make the sound they wanted, based on the criteria of their choice. Once the participants were satisfied with the sound they created, they moved onto the next trial by clicking the ‘Validate’ button. There was no time limit.

The sounds were presented through headphones (AKG K52) and were generated in real time using the Max/MSP software (https://cycling74.com/), according to the parameters set by the participants. Each participant designed the four stimuli. The order of the condition presentation was randomized.

The participants were then invited to take part in a semi-structured interview with the experimenter, aimed at understanding how they approached the sound construction process and the reasons behind their choices. The interview had the same structure for each participant. The interview began with a general question, in which the experimenter asked participants to describe their experience during
the sound creation process. Then, each sound they created was presented to them. For each sound, the following questions were asked:

- Can you describe this sound?

- If you had to find an image or a word to describe this sound, what would it be?

- Why did you choose this sound rather than another?

After that, questions about any difficulties encountered during the experiment were asked. The experimenter also asked which of the 4 sounds they constructed they preferred, which one they liked the least, and why. The audio interview was recorded with the prior consent of the participants for the recording. The recordings were then transcribed using the noScribe software (v0.6.2, [5]) and manually corrected afterwards.

# 3 Preliminary results

## 3.1 Intra-class correlation

We computed intraclass correlation coefficient (ICC) on the carrier and beating frequencies data for each type of stimuli. ICC is generally used to assess the consistency of quantitative measurements made by different evaluators. It compares the variability of different ratings of the same object to the total variation across all ratings and all objects. The ICC values vary between 0 and 1. ICC estimates were calculated using irr package for R based on single rater, absolute agreement, 2-way mixed-effects model, with 16 raters (participants) and 2 rated objects (fundamental and beating frequency values). Results showed a moderate agreement between participants for the monaural [ICC = 0.651; $F(1, 29.8) = 29.3$] and BB ([ICC = 0.641; $F(1,30) = 30.9$] and alternate beeps [ICC = 0.613; $F(1,29.9) = 26.1$]. For the panning beats condition, we found a good agreement with ICC = 0.815 [$F(1,29.8) = 67$].

## 3.2 Sound preference

Concerning preferred sound (Table 1), no clear preference emerged but there is a tendency for BB with 31,25% of participants who chose it as preferred sound. Interestingly, we found the same tendency for BB with 37, 5% for the less preferred sound. To examine the participants preferences, we calculated the median fundamental and beating frequencies for each type of stimuli: 1) Monaural beats: median $f_0 = 157.68$, median $f_b = 4.88$; 2) BB: median $f_0 = 202.8$, median $f_b = 3.89$; 3) Panning beats: median $f_0 = 134.98$, median $f_b = 2.43$; 4) Alternate beeps: median $f_0 = 233.59$, median $f_b = 6.73$. These median values allowed us to divide our sample into two groups: those who selected frequencies below the median and those who selected frequencies above it. Table 2 shows, for each preferred sound, the percentage of participants who chose fundamental and beat frequencies either above or below the median. Participants who preferred
monaural sounds or BB mostly selected fundamental and beat frequencies below the median (i.e., lower frequencies relative to our sample). In contrast, when panning beats were the preferred sound, there did not appear to be a clear difference in preference based on the fundamental or beat frequencies. For those who preferred alternate beeps, the selected fundamental frequency was predominantly below the median. However, the beat frequency chosen did not appear to influence preference in this condition.

<table><caption>**Table 1.** Percentage of preferred and less preferred sound with respect to the type of stimuli.</caption><thead><tr><th>Sound</th><th>Preferred sound (in %)</th><th>Less preferred sound (in %)</th></tr></thead><tbody><tr><td>Monaural beats</td><td>18,75</td><td>18,75</td></tr><tr><td>Binaural beats</td><td><strong>31,25</strong></td><td><strong>37,5</strong></td></tr><tr><td>Panning beats</td><td>25</td><td>25</td></tr><tr><td>Alternate beeps</td><td>25</td><td>18,75</td></tr></tbody></table>

<table><caption>**Table 2.** Percentage of preferred sound depending on fundamental and beating frequencies.</caption><thead><tr><th></th><th>Monaural beats</th><th>Binaural beats</th><th>Panning beats</th><th>Alternate beeps</th></tr></thead><tbody><tr><th>f<sub>0</sub> &lt; median</th><td><strong>66,67</strong></td><td><strong>80</strong></td><td>50</td><td><strong>75</strong></td></tr><tr><th>f<sub>0</sub> &gt; median</th><td>33,33</td><td>20</td><td>50</td><td>25</td></tr><tr><th>f<sub>b</sub> &lt; median</th><td><strong>66,67</strong></td><td><strong>80</strong></td><td>50</td><td>50</td></tr><tr><th>f<sub>b</sub> &gt; median</th><td>33,33</td><td>20</td><td>50</td><td>50</td></tr></tbody></table>

We did the same process with the less preferred sound. The results showed that when monaural beats are the less preferred sound, the chosen fundamental frequency is above the median (Table 3, 66.67%) and the beating frequency is below the median (66.67%). A similar tendency was observed when alternate beeps are less preferred. No effect of fundamental or beating frequency appears for the panning beats. However, when BB are less preferred, 83.33% and 66.67% of the participants chose fundamental and beating frequencies above the median, respectively.

<table><caption>**Table 3.** Percentage of less preferred sound depending on fundamental and beating frequencies.</caption><thead><tr><th></th><th>Monaural beats</th><th>Binaural beats</th><th>Panning beats</th><th>Alternate beeps</th></tr></thead><tbody><tr><th>f<sub>0</sub> &lt; median</th><td>33,33</td><td>16,67</td><td>50</td><td>33,33</td></tr><tr><th>f<sub>0</sub> &gt; median</th><td><strong>66,67</strong></td><td><strong>83,33</strong></td><td>50</td><td><strong>66,67</strong></td></tr><tr><th>f<sub>b</sub> &lt; median</th><td><strong>66,67</strong></td><td>33,33</td><td>50</td><td><strong>66,67</strong></td></tr><tr><th>f<sub>b</sub> &gt; median</th><td>33,33</td><td><strong>66,67</strong></td><td>50</td><td>33,33</td></tr></tbody></table>
## 3.3 Evocation of sounds

We also analyzed the responses of participants to the question: "If you had to describe this sound with a word or an image, what would it be?". Based on their answers, we identified five categories of evocations:

- Sounds that evoke an object (e.g., "metronome");

- Sounds that evoke an atmosphere or mood (e.g., "it feels like we're in the future, shifting dimensions");

- Biological or living-related sounds (e.g., "flat electrocardiogram", "cat purring");

- Sounds that evoke a sensation (e.g., "it feels like I'm between two vibrating walls");

- Sounds that evoke an action (e.g., "it's the sound made when you rub a wet finger on a glass").

Table 4 presents the percentage of responses that fall into each category, by condition. The monaural beats most frequently evoked an object for 47.62% of the participants. In particular, they often brought to mind alarm-like objects or events such as "beeping sounds", "flashing lights", "sirens", or "waves", suggesting a sense of alternation or something that disappears and returns. In contrast, BB gave rise to more varied associations: 29.41% of the participants described them as biological sounds (e.g. "a bumblebee", "cardiac, blood"), 23.53% as an atmosphere (e.g. "underground", "post-apocalyptic films"), and 17.65% as evoking an object (e.g. "a clock", "a pure sinusoid"). Panning beats were most often associated with an atmosphere (42.86% of the participants, e.g. "industrial", "laboratory"), and nearly half of them specifically described a science-fiction-like atmosphere (e.g. "alien films from the 80s", "we're in the future, we're changing dimension"). Finally, alternate beeps evoked an object for 36.84% of participants and an atmosphere for 31.58%. They were often associated with machinery (e.g., "engine", "helicopter blades", "washing machine spin cycle" or "robot computer noises").

<table><caption>**Table 4.** Percentage of response depending on the category of the evocation.</caption><thead><tr><th>Categories</th><th>Object</th><th>Atmosphere</th><th>Biological</th><th>Sensation</th><th>Action</th></tr></thead><tbody><tr><td>Monaural beats</td><td><strong>47,62</strong></td><td>23,81</td><td>14,28</td><td>0</td><td>0</td></tr><tr><td>Binaural beats</td><td>17,65</td><td><strong>23,53</strong></td><td><strong>29,41</strong></td><td>11,76</td><td>5,88</td></tr><tr><td>Panning beats</td><td>28,57</td><td><strong>42,86</strong></td><td>0</td><td>9,52</td><td>4,76</td></tr><tr><td>Alternate beeps</td><td><strong>36,84</strong></td><td><strong>31,58</strong></td><td>10,53</td><td>10,53</td><td>5,26</td></tr></tbody></table>

## 4 Discussion

Our main hypothesis was that, similar to the concept of a *preferred tempo*, each individual has a preferred fundamental frequency and beat frequency. Furthermore, we hypothesized that, despite being subjective, there would be some degree of agreement or consensus within the population around a specific frequency
range. The computation of ICC values (section 3.1) revealed moderate to good levels of agreement between participants. These results suggest a certain consistency in the frequency values chosen by participants. The ICC was particularly high in the panning condition, which is also the one where the perception of movement was strongest and spatial cues were most salient. This salience likely facilitated agreement among participants by making frequency adjustment easier. In the other conditions, ICCs were moderate, indicating a greater influence of individual factors in sound construction compared to the panning condition.

Regarding preference, responses were relatively balanced across the different conditions. This result supports the idea that the effect of an auditory stimulus on a listener's psychological state requires an individualized approach. Indeed, it is difficult to imagine that a sound we dislike could help us relaxing or improving our attention. The fact that BB were both the most and the least liked by participants clearly illustrates this point. However, when examining preferences based on fundamental frequency, it appeared that participants chose low-frequency sounds. Conversely, the least liked sounds were generally higher pitched. As for beating frequency, preferred monaural and BB were mostly low frequency. In contrast, beating frequency did not seem to influence the preference for alternate beeps. Interestingly, when monaural beats and alternating beeps were the least liked sounds, their beating frequencies were also low frequency, whereas disliked BB tended to have beating of high frequencies. These patterns did not apply to the panning condition, where neither fundamental nor beat frequency appeared to correlate with participants preference. Taken together, the results suggested that fundamental frequency plays a significant role in auditory preference: for a sound to be appreciated, it must generally have a low fundamental frequency. It is also noteworthy that the median fundamental frequency for preferred BB was 202 Hz. This value is half the value typically used in most BB studies, which often center around 400 Hz. Thus, lowering the fundamental frequency of BB in future experiments may enhance their effectiveness.

The reported evocations induced by sound were rich and diverse, reflecting the complexity of the perceptual experience induced by the auditory stimuli. However, each type of sound seemed to elicit specific kinds of mental imagery. Monaural beats and alternating beeps mainly evoked objects, although the nature of these objects differed between the two conditions. Binaural beats, on the other hand, generated more varied associations, including biological sounds. Panning sounds primarily evoked atmospheric impressions, particularly related to science fiction. The richness of these evocations highlights the importance of considering not only the acoustic properties of sounds but also their emotional and symbolic dimensions in studies on human perception.

Altogether, these results suggest that there are no universal rules regarding preference or the imagery evoked by auditory stimuli that can be applied to all listeners, reinforcing the need for an individualized approach. This could help, in particular, to improve the effects of binaural beats, and more generally of spatialized sounds, on cognitive states and to partly explain the contradictory results reported in the literature on this topic. It is important to note that this
study is still ongoing. The obtained tendencies will have to be consolidated with
more participants. The next step of this study is to evaluate the individualization
of sound stimuli in the context of their impact on the mental states of the
listeners. Future research could also explore how these evocations and preferences
evolve over time even for a given listener. Indeed, the sound productions collected
here reflect participants at a specific moment in time. It would therefore be
interesting to examine how these productions shift or develop, as a reflection of
individuals in constant evolution.

**Acknowledgments.** We thank Jocelyn Rozé for his help in developing the sound stimuli and the interface. This work, carried out within the Institute of Convergence ILCB (ANR-16-CONV-0002), has benefited from support from the French government (France 2030), managed by the French National Agency for Research (ANR) and the Excellence Initiative of Aix-Marseille University (A*MIDEX).

**Disclosure of Interests.** The authors have no competing interests to declare that are relevant to the content of this article.

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