Auditory Spatial Perception as a Function of Recreational Noise Exposure in Gen-Z Adults with Normal Hearing

Abstract

The study aimed to evaluate auditory spatial perception in individuals with and without recreational noise exposure using Virtual Acoustic Space Identification. A standard group comparison design using purposive sampling was conducted on 60 normal-hearing participants aged 18–30. They were divided into experimental and control groups based on their scores on the recreational hearing habits questionnaire (CHAR). The experimental group was exposed to recreational noise for at least 4 h per day, while the control group had no noise exposure. The procedure involved the administration of Virtual Acoustic Space Identification (VASI) at 65 dB SPL. Spatial perception was measured at eight spatial percepts within the head. Based on the confusion matrix, accuracy scores, reaction time at each virtual location, and the overall VASI score were calculated. The results indicate a significant difference in Front errors and Front-as-back errors in the two groups; people with recreational noise exposure had more errors in these spatial percepts. This indicates the differential impact of recreational noise on auditory spatial perception. The differences observed in the test can be attributed to the complexity of the auditory spatial perception task, the stimulus and the better sensitivity of the VASI in detecting spatial deficits. Recreational noise exposure affects spatial auditory perception, emphasizing the importance of mitigating recreational noise-related risks for auditory spatial skills.

Introduction

Urbanization and modernization have heightened our ongoing contact with environmental noise. Recreational noise, derived from activities like music festivals, sporting events, nightlife, and personal music devices, emerges as a substantial component of the everyday soundscape [1]. Hearing loss in adults is most frequently caused by environmental noise exposure. Noise-induced hearing loss (NIHL) transpires from exposure to daily noises, including loud concerts, portable media players, and public transport [2, 3]. In modern life, unexpected noise exposure is pervasive and has led to an alarming increase in NIHL instances, particularly among the younger population [4].

Recreational noise exposure can be defined as voluntary exposure to noise during leisure time, which may be a risk factor for developing hearing loss [5]. Several studies reported elevated pure-tone thresholds in individuals using Personal Listening Devices (PLD) [6, 7]. However, other studies have not found significant changes in hearing thresholds [8, 9]. It is important to check if the high recreational noise exposure could also affect the hearing function beyond the standard pure tone audiogram and may affect the auditory processing ability. Several studies further indicated that cochlear synaptopathy might be the primary cause of hearing difficulties in individuals with normal hearing thresholds exposed to noise from their PLD. This phenomenon of normal hearing despite having auditory processing deficits subsequent to cochlear synaptopathy is termed as referred to as “hidden hearing loss” [10–12]. After a lifetime of PLD noise exposure, cortical degradation affects the temporal aspects of neuronal responses and differs from the rate-related effects observed after three months of exposure [13].

Current knowledge about hazardous recreational noise levels is mainly based on results from cross-sectional studies, and there seems to be a lack of consistency in methods of measuring hearing function and noise exposure. Most of the results regarding evidence of hearing loss due to recreational noise exposure showed signs of ≥ 15–25 dB HL TTSs (one or both ears) for single frequencies and mostly above 1 kHz or in the extended high frequency (EHF) range. Reduced amplitudes of transient evoked otoacoustic emission (TEOAE)/ distortion product otoacoustic emission (DPOAE) are also reported [14].

After a lifetime of noise exposure, cortical degradation affects the temporal aspects of neuronal responses and differs from the rate-related effects observed after three months of exposure [13]. By comparing cases with either very high- or very low-noise exposures, the impact of noise exposure on auditory processing and/or speech-in-noise measures may be more evident. Auditory spatial perception, which is a part of auditory processing, can also be subjected to this effect. Auditory spatial perception is the human capacity to localize sound sources in the surrounding environment, a fundamental skill essential for safety, communication, and overall quality of life [15]. This perceptual function relies on the auditory system’s ability to process complex auditory cues, which are critical for sound localization. Deficits in spatial hearing secondary to hearing loss have a direct bearing on day-to-day communication in listening environments [16], such as listening in noise [17] and reverberation [18].

Virtual auditory space identification (VASI) is a novel paradigm that relies on auralization techniques to synthesize spatial percepts called virtual acoustic stimuli, which cause an illusionary effect of natural sound-field localization within the head [19]. The virtual stimuli are constructed by superposing the target stimuli with the non-individualized HRTFs (refer to stimulus generation methods), enriching the stimuli with important spatial cues such as the ITDs, ILDs, spectral, and HRTFs [20]. Virtual Acoustic Space Identification (VASI) test simulates the sound locations virtually in the head which is used extensively to study spatial perception [21]. VASI test simulates the sound locations virtually in the head which is used extensively to study spatial perception.

The increased use of smart phones is a growing concern among the young adults [22]. Today’s teenagers and young adults including those born after the year 1997 till 2012, known as Gen Zoomers (Gen Z) have essentially been exposed to the digital environment and smartphones since birth [23]. They have grown up in a world saturated with technology, which has shaped their behaviours and preferences in many areas, including their use of audio devices [24]. The overuse of earphones and excessive dependence on smartphones are emerging as important reasons for health realted problems in this generation of young adults. Additionally, a comprehensive survey and analysis emphasized that Generation Z’s reliance on mobile devices extends to their academic environments, where earphones are commonly used for listening to educational content, music, and other recreational purposes [24]. Although the deleterious effect of high levels of recreational noise, especially in Gen Z, is speculated to cause long-term effects on their auditory processing, the link between recreational noise exposure and auditory spatial perception is not well understood. Studies are required to enhance understanding of the long-term impacts of recreational noise and headphone use on hearing’s spatial perception. Longitudinal studies comparing individuals with varying degrees of music exposure to PLDs are necessary. This study investigates the effect of considerable PLD noise exposure on spatial hearing abilities in individuals with normal hearing.

Method

Research Design

A standard group comparison design by Orlikoff [25] using purposive sampling.

Participants

Sixty participants in the age group of 18–27 years were included in the study. They were divided into two groups of 30 based on their recreational noise exposure. Recreational Hearing Habits Questionnaire (CHAR) [26] was used to classify the groups into experimental (Mean age = 20.74 ± 1.67 y) and control (Mean age = 20.55 ± 1.61 y) groups. The individuals without significant noise exposure were grouped as the control group, and those with significant noise exposure were grouped as the experimental group. All the participants had normal hearing sensitivity. The participants in the study were university students and informed consent was obtained from all of them before the start of the study.

Prior to administering the auditory spatial tests, all participants underwent pure tone audiometry using the modified Hughson Westlake method for frequencies ranging from 250 to 8 kHz. Immittance audiometry was performed where tympanometry was done using 226 Hz probe tone and acoustic reflexes were checked, to rule out middle ear and neural dysfunction. All the participants had normal hearing sensitivity (≤ 25 dB HL) from 250 Hz to 4 kHz for air and bone conduction thresholds. Immittance results showed that an ‘A’ type tympanogram with acoustic reflexes was present in all the participants of the study.

Following the inclusion of the participants, the “CHAR” questionnaire was administered to all participants. CHAR is a self-administered tool designed to assess listening habits and exposure to recreational noise among adolescents and young adults. It contains 24 questions with multiple-choice options, covering various aspects such as characteristics of personal music players, period, frequency and context of use, attendance to concerts, and attendance to other noisy venues. All the participants in the exposed group had the habit of listening to the recreational noise for at least 4 h/ day, above the warning intensity levels on their devices.

The spatial test, VASI was administered to all the participants. The intensity of the stimuli was calibrated to 65 dB SPL. Microphone 2050 was kept in the ear of a mannequin (KEMAR), which read the output. This output was connected to SLM4450, and the volume control in the laptop was set at a level that matched the 65 dB SPL output in SLM. VASI was administered according to the standard procedure recommended by Nisha et al. [27]. Spatial perception was measured at eight spatial percepts within the head: midline front (0° azimuth), midline back (180° azimuth), 45° toward the right ear (R45), 90° toward the right ear (R90), 135° toward the right ear (R135), 45° toward the left ear (L45), 90° toward the left ear (L90), and 135° toward the left (L135). Stimuli from each virtual location were calibrated at 65 dB SPL and were randomly presented ten times at each location, making up 80 trails. The test was completed in 10 min, and the output was stored in spreadsheet.

The test-retest reliability of VASI has been proven to be accurate [27]. The interclass co-efficient of correlation values ranged from 0.60 to 0.86 (mean 0.77 ± 0.12 SD) and 0.60 to 0.84 (mean 0.75 ± 0.09 SD) for VASI accuracy and reaction time, respectively, indicative of moderate to high reliability across different virtual locations tested. Similarly, the ICC obtained for overall VASI accuracy (0.93) was also high, suggestive of a high degree of similarity in VASI scores across the three timelines of measurements used in the previous study [27]. Spatial perception evaluated using VASI measured under headphones was also found to have good correlation with spatial acuity measured in sound-field [28]. The relationships between the two paradigms were characterized by a strong overall correlation (0.7 and above) and a moderate correlation (0.4 to 0.56) for location-specific accuracy and reaction time respectively, indicative that VASI can be reliable tool to estimate auditory spatial perception abilities (See Fig. 1)

Fig. 1.

Schematic representation of spatial hearing test setup (VASI) used in the study

The output stored in Excel was analyzed using a custom formula run using Matlab script (Gnanateja, 2014) to obtain a confusion matrix containing a stimulus-response contingency table. From this table, four metrics of spatial hearing, namely (1) Accuracy scores, (2) Pattern of spatial errors, (3) Reaction time of correct responses, and (4) reaction time pattern of spatial accuracy scores, were obtained for each virtual location along with the overall accuracy score. Spatial errors were analyzed following the literature recommendations of previous studies. The errors computed included azimuth error in the right hemifield (average error of the three right plane virtual locations : R45, R90, R135), azimuth error in left hemifield (average error of the three left plane virtual locations: L45, L90, L135). Whenever front was perceived as back and back was perceived as front, these were considered to be front as back error(0 as 180) and back as the front error (180 as 0), respectively. The rationale for calculating front-back errors and back-to-front separately was to avoid getting an inflated localization error [29–31]. On similar lines, reaction time at each virtual location and overall VASI reaction time was calculated along with the reaction time errors (right error, left error, front as back error and back as front error).

Statistical Analyses

All the scores obtained for VASI were loaded to Statistical package for Social Sciences (SPSS) version 25.0 software (IBM Corp.; Armonk, NY, USA). Test of normality was conducted using Shapiro Wilk’s test. To compare between the auditory spatial abilities of two groups, Independent sample t-test was performed for data that adhered to normality, while Mann Whitney test was for non-normal distributed data. Whenever significant group differences were found, Cohen’s d [32] and Rosenthal’s size [33] is reported, as need be.

Results

Shapiro Wilks’ test showed normality (p > 0.05) for the VASI test (both location-wise and overall scores). In the VASI test, the Gen Z adults with recreational noise exposure scored significantly lower than those with noise exposure on overall VASI [t(58) = 3.66, p = 0.001; cohen’s d = 0.94] and VASI scores in the frontal locations [0 : t(58) = 3.03, p = 0.004, cohen’s d = 0.78 ; R45 : t(58) = 2.81, p = 0.007, cohen’s d = 0.73; L45: t(58) = 2.92, p = 0.005, cohen’s d = 0.75] as shown in Fig. 2. However, this trend was not observed for other virtual locations, as shown in Table 1. For the parameter reaction time, the overall and location-specific reaction time of the two groups did not differ significantly from each other as shown in Fig 3.

Fig. 2.

Comparison of VASI accuracy scores of Gen-Z participants with and without recreational noise exposure. The inner dummy head corresponds to the VASI interface, depicting the eight virtual locations used in the study. The panels corresponding to each virtual location denote the corresponding VASI accuracy scores, with the centre line of box plot showing the mean and the error bars denoting the one standard deviation (SD). The overall VASI scores of the two groups is shown in the highlighted panel (vilon plot). The width of the vilon plot represents density of observations

Table 1.

Effect of recreational noise exposure on spatial perception (VASI accuracy and reaction time) scores in Gen Z adults. Whenever significant differences were found, effect size, cohen’s d is reported

Azimuth	Accuracy scores		Reaction time scores
	t(58) =	p value, cohen’s d	t(58) =	p value
Overall	3.66	0.001, 0.94	0.39	0.69
0°	3.03	0.004, 0.78	1.87	0.07
180°	1.62	0.11	0.12	0.91
R45°	2.81	0.007, 0.73	0.17	0.87
R90°	0.71	0.48	0.03	0.98
R135°	0.59	0.56	0.34	0.74
L45°	2.92	0.005, 0.75	0.85	0.40
L90°	0.48	0.63	1.09	0.28
L135°	0.41	0.69	0.62	0.54

Fig. 3.

Comparison of VASI reaction time scores of Gen-Z participants with and without recreational noise exposure. The inner dummy head corresponds to the VASI interface, depicting the eight virtual locations used in the study. The panels corresponding to each virtual location denote the corresponding VASI reaction time scores, with the centre line of box plot showing the mean and the error bars denoting the one standard deviation (SD). The overall VASI reaction time scores of the two groups is shown in the highlighted panel (vilon plot). The width of the vilon plot represents density of observations

When the pattern of errors were analysed, the mean errors and reaction time of noise-exposed Gen Z adults made while identifying front sound (confused as as back) was higher than non-exposed individuals (0.73 ± 0.94), although this difference was not statistically significant, as shown in Table 2. Other errors and reaction times were comparable between the two groups (Table 2).

Table 2.

Comparison of the errors in location identification and reaction time at different spatial percepts between groups

Type of error	Target and perceived location	Mean ± Standard deviation		t(58), p
		Noise exposed	No noise exposure
Location Identification	Front as back	1.70 ± 1.98	0.73 ± 0.94	2.41, 0.20
	Back as front	0.73 ± 0.98	0.93 ± 1.50	0.60, 0.54
	Right error	4.65 ± 1.35	4.18 ± 0.94	1.54, 0.12
	Left error	6.01 ± 1.05	6.14 ± 1.00	0.46, 0.64
Reaction time (in ms)	Front as back	1797.93 ± 1860.93	1088.32 ± 1371.84	1.68, 0.09
	Back as front	1170.31 ± 1692.97	870.95 ± 1166.59	0.80, 0.42
	Right error	2704.19 ± 1152.47	2921.65 ± 1106.52	0.74, 0.45
	Left error	2954.02 ± 1924.30	2414.75 ± 862.80	1.40, 0.16

Discussion

In general, the results of the study suggest that recreational noise exposure may have a negative impact on auditory spatial abilities in gen Z participants, as evidenced by the significant differences in overall VASI accuracy scores (Table 1). Recreational noise exposure, such as that from bars, parties, and other public spaces, can significantly impact the identification of sounds in acoustic spaces [34]. The impact of such exposure on sound identification may be due to the confusion errors that occur in the presence of similar temporal patterning in the sounds [35]. Research has shown that recreational noise exposure can have a significant impact on individuals’ hearing and perception of sound. Kariel [36] found that sound pressure level alone is not a good predictor of spatial perception, suggesting that other factors, such as the harmonic content of the sounds and socio-psychological aspects may play a role. This is supported by Tung and Chao [37], who found that teenage students with high levels of recreational noise exposure were more likely to have hearing problems. Solomos [38] further validated the impact of recreational noise exposure, developing a questionnaire to assess listening habits and levels of noise exposure in young people. These findings suggest that recreational noise exposure can affect individuals’ ability to identify virtual acoustic spaces, potentially due to changes in their perception of sound. The differences observed in the VASI test can be attributed to the complexity of the auditory spatial perception task (VASI involves identification task), the stimulus used (VASI has composite cues for spatial perception), the selective impact of recreational noise exposure on different aspects of auditory processing, and the better sensitivity of the VASI in detecting spatial deficits.

Specifically, the results showed that the Gen Z adults with recreational noise exposure had significant decrease in accuracy of front sound (0°) that was judged as originating from extreme back (180°, front-back errors) (Fig. 2; Table 1). Similar confusions were also seen for frontal sounds (R45, L45) which were instead confused to be originating much laterally (R45 confused as R90, L45 confused as L90) in the recreational noise exposure group. This finding showed that recreational noise exposure group demonstrated poorer auditory spatial perception accuracy, due to their impaired ability to correctly identify frontal sounds. This impairment is exacerbated by the lack of individualized Head-Related Transfer Functions (HRTFs), which are crucial for accurate sound localization. Non-individualized HRTFs, common in virtual auditory environments, fail to account for unique anatomical features, leading to increased localization errors [39, 40]. Additionally, the absence of visual cues and head movement during the VASI test further challenged the recreational noise group [41, 42].

When considering reaction time measures, there was no significant difference between the two groups. This suggests that temporal processing (ability to arrive at a decision of spatial location) is less impacted by exposure to recreational noise in Gen Z listeners. Despite the fact that the response time depended on the participants’ discretion (i.e., the next stimulus was presented only after the participant registered a response) during the test phase, both groups judged sound locations in approximately the same amount of time. All the participants in the study were asked to respond as soon as possible after they judged the location of the spatial stimuli. Increasing system latency for response in a virtual acoustic environment minimally impacts localization accuracy, as listeners can adapt to latency during active listening [43]. This adaptation might explain the lack of significant difference in reaction time.

Studying the impact of recreational noise on the present generation of Gen Z younger adults has a lot of clinical implications. The distortion of spatial references due to noise exposure can impact localization, confuse the listener, and influence response times. The capacity to swiftly identify and adapt to important targets is crucial for the safety and effectiveness of various emergency personnel dedicated to public welfare, including traffic police, firefighters, and emergency medical responders who frequently react to life-threatening situations under stressful and dangerous circumstances. Spatial awareness and orientation are also critical for professionals like pilots and drivers, where slight changes in sound direction and intensity can offer valuable information for safe navigation and decision-making. Counseling the current gen Z of the impact of recreational noise and its relevance in professionals and the general public (which they may be a part of in future) can significantly improve their understanding of potential risks.

The study was limited by the absence of individual data on noise exposure duration and the inability to control for musicians’ presence in both groups. VASI does not include head movements in its design. Horizontal plane front-to-back errors with free head movement (like in free-field) cannot be evaluated. The application of VASI results to everyday spatial perception requires additional subjective ratings. The study’s future focus includes measuring the effects of recreational noise exposure on spatial perception through a combination of VASI test results and self-reported speech, spatial, and hearing quality questionnaires.

Conclusions

Findings from the investigation revealed the impact of recreational noise exposure on spatial auditory perception, in the current Gen Z adults. Mitigating recreational noise risks is crucial for preserving auditory spatial skills, particularly in young adults.

Declarations

Ethical Approval

The study strictly adhered to ethical guidelines established for bio-behavioral research, as outlined byBasavaraj and Venkatesan in 2009 (Reference Number- SH/UG05/2023-24).

Informed Consent

Before participating in the survey, informed consent was diligently obtained from each participant.

Conflict of interest

The authors declare no conflict of interest. The authors have no relevant financial or non-financial interests to disclose.