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 Table of Contents  
ORIGINAL ARTICLE
Year : 2016  |  Volume : 22  |  Issue : 2  |  Page : 85-91

Effect of musical training on masking paradigm


1 Department of Audiology, All Institute of Speech and Hearing, Mysuru, Karnataka, India
2 Department of Tele Centre for Persons with Communication Disorder, All Institute of Speech and Hearing, Mysuru, Karnataka, India

Date of Web Publication11-May-2016

Correspondence Address:
N Devi
Lecturer in Audiology, All India Institute of Speech and Hearing, Mysuru - 570 006, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-7749.182280

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  Abstract 

Background: Musicians outperform nonmusicians on brainstem and cortical level processing. However, there are limited literature comparing musicians and nonmusicians on the overall release of masking abilities and correlation across otoacoustic emissions (OAEs), masking level difference (MLD) and quick speech-in-noise (Quick-SIN). Aim: To investigate the physiological differences between musicians and nonmusicians by evaluating the effect of musical training on contralateral suppression (CAS) of OAE, MLD, and Quick-SIN. Materials and Methods: Distortion product OAEs (DPOAEs) recording with and without noise, MLD test using continuous (CMLD) and pulsating pure tones (PMLD) and Quick-SIN in Kannada were carried out on 15 musicians and 15 nonmusicians. Results: Musicians outperformed nonmusicians on Quick-SIN and CAS of OAEs. However, no significant difference was observed between two groups on CMLD and PMLD. There was a significant difference observed in CMLD, PMLD as well as suppression amplitude across frequencies tested in both groups. A significant difference between PMLD and CMLD was observed only for musicians at 2 kHz. In both groups, there was a significant level of correlation for CAS of DPOAE and Quick-SIN with CMLD and with PMLD between the parameters tested. Conclusion: The results of our finding suggest that CAS of DPOAE and Quick-SIN are sensitive tools to quantify the effect of musical training, compared to MLD. Musical training helps to strengthen afferent and efferent pathways, and hence it aids in speech perception abilities in noise. Hence, for the intervention of individuals with difficulties in speech perception in noise, musical training can be a choice to be considered. As well for appropriate diagnosis and interpretation, one needs to consider the musical experience of individual tested.

Keywords: Correlation, Musical expertise, Musical training, Speech perception


How to cite this article:
Devi N, Swathi C S. Effect of musical training on masking paradigm. Indian J Otol 2016;22:85-91

How to cite this URL:
Devi N, Swathi C S. Effect of musical training on masking paradigm. Indian J Otol [serial online] 2016 [cited 2019 Nov 15];22:85-91. Available from: http://www.indianjotol.org/text.asp?2016/22/2/85/182280


  Introduction Top


Processing of speech in the presence of noise is one of the major functions of the olivocochlear efferent pathway.[1] Medial olivocochlear (MOC) efferent system functioning can be understood by measuring otoacoustic emissions (OAEs) with and without noise and quick speech-in-noise (Quick-SIN). Another way of studying the release of masking is by measuring masking level difference (MLD). The combination of Quick-SIN, MLD and contralateral suppression (CAS) of OAEs provide information on masking and overall release of masking and gives an overall picture on afferent and efferent pathway functioning.

Musical training results in different structural and functional changes which in turn, is exhibited in the form of improvements in different domains including speech perception abilities in background noise.[2] Musicians are reported to exhibit greater CAS of OAEs [3],[4],[5],[6] and better performance in Quick-SIN [2],[7] compared to nonmusicians. The MLD is a binaural interaction task, where accurate auditory processing is required. However, the performance by musicians for MLD task is expected to be better compared to nonmusicians.

There is a dearth in literature which focuses on musician's response to masking paradigm relative to nonmusicians. Hence, this study will throw more light on the effect of musical training on masking and overall release of masking. Furthermore, there is a limited literature which has extensively studied about correlation across Quick-SIN, MLD and CAS of OAEs between musicians and nonmusicians. As the current study uses a combination of different tests which assess the afferent and efferent functioning, it will give more insight on existing knowledge about the relative strength of these pathways between musicians and nonmusicians. Hence, this study was aimed to evaluate the effect of musical training on MLD (continuous and pulsating tones), speech perception abilities in noise and CAS of OAEs and to compare the overall release of masking and masking effects between musicians and nonmusicians.


  Materials and Methods Top


Participants

A total of thirty individuals with the normal auditory system were included in the study. They were classified into two groups with 15 participants each, based on their musical training experience. Group 1 included individuals aged between 18 and 35 years (mean = 20.67, standard deviation [SD] = 1.63; five males, ten females) who had undergone at least 5 years of formal classical music training (musicians) and Group 2 included individuals aged between 18 and 35 years (mean = 20.67, SD = 2.58; six males, nine females), who had not undergone any formal training for music (nonmusicians).

Test environment

All tests were carried out in acoustically treated room where noise levels were within permissible limits.[8]

Instrumentation

Calibrated two channel Inventis Piano Plus audiometer coupled to impedance matched TDH 39 earphones housed with MX-41/AR cushions and a bone vibrator (Radio ear B-71) were used to carry out pure tone audiometry, speech audiometry, and MLD testing. Calibrated two channel GSI AudioStar Pro audiometer was used to carry out Quick-SIN testing. Calibrated GSI TympStar (Grason-Stadler Inc.) middle ear analyzer was used for tympanometry and reflexometry. A calibrated otoacoustic emission system, ILO v6 (Otodynamics Ltd., Hatfield, UK) was used for measuring distortion product OAEs (DPOAEs). The contralateral noise was presented using calibrated two channel Inventis Piano Plus audiometer through insert receiver.

Procedure

Before the actual procedure, written consent was taken from the participants for their willingness to participate in the study. Pure tone audiometry was carried out using modified Hughson and Westlake method [9] for obtaining air conduction thresholds at octave frequencies (250 Hz–8 kHz) using TDH 39 earphones and bone conduction thresholds for octave frequencies (250 Hz–4000 Hz) using Radio ear B-71. Speech identification scores were obtained using a phonemically balanced word list.[10] Tympanometry was administered using 226 Hz probe tone, and ipsilateral and contralateral reflexes were obtained at 500 Hz, 1 kHz, 2 kHz, and 4 kHz to rule out the middle ear pathology.

Quick speech-in-noise

Speech perception ability in noise was measured using the signal to noise ratio (SNR)-50, which is the SNR, required understanding 50% of the presented speech in the presence of competing signal. The test stimuli developed by Avinash et al.[11] was used with 3 dB steps.[12] SNR-50 was measured in the presence of four-talker babble presented binaurally, routed through headphones via audiometer connected to the computer. Each list contains seven sentences in Kannada with five keywords each. The SNR was decreased in 3 dB steps from +8 dB SNR to −10 dB SNR for every succeeding sentence from 1 to 7 in each list. These sentences were presented at 70 dB HL through the audiometer. The participants were asked to listen to the sentences and repeat back the target sentences heard in the presence of multi-talker babble at different SNRs. At each SNR, the number of correct keywords identified were counted and scores were calculated using Spearman–Karber equation [13] as: SNR-50 = I + ½ (d) − (d) (# correct)/(w), where I = initial presentation level (dB S/B), d = attenuation step size (decrement), w = number of keywords per decrement, # correct = total number of correct keywords.

Masking level difference

Thresholds of the participants for narrow-band noise were found with TDH 39 earphones were found initially. Later, they were instructed to respond only to tone in the presence of noise. The MLD testing was carried out using continuous and pulsating tone at 250 Hz, 500 Hz, 1 kHz, 1.5 kHz, and 2 kHz binaurally in two conditions. That is, homophasic condition (S0N0 - Signal and noise in phase in both ears) and antiphasic condition (SπN0 - Polarity of signal 180° out of phase in one of the ears, with noise in phase in both ears). Homophasic condition: The level of noise was kept constant at 40 dB SL and the threshold of the tone was found (Thomophasic) in 2 dB steps. Antiphasic condition: The level of noise was kept constant at 40 dB SL and the threshold of the tone was found (Tantiphasic) in 2 dB steps. Once both the thresholds were obtained, MLD was calculated by substracting Tantiphasic from Thomophasic, MLD = Thomophasic − Tantiphasic.

Contralateral suppression of otoacoustic emission

The probe tip of Otodynamics Ltd., ILO version 6 was placed in the ear canal to get a good seal. The total testing included two baseline recordings in the absence of noise and two recordings in the presence of contralateral noise. The right ear was used for testing as contralateral acoustic suppression was reported to be more for the right ear.[4] The probe was positioned in the test ear canal and was adjusted to maintain a flat stimulus frequency spectrum. DPOAEs were obtained using two pure tones of frequencies f1 and f2 and intensities at L1 and L2, respectively. f2/f1 ratio was maintained constant at 1.22. The intensity of two stimuli, L1 and L2 were kept constant at 65 and 55 dB SPL, respectively. OAEs were considered present only if it was at least 6 dB above the noise floor.[14] Noise thresholds were obtained using ER-3A insert earphones of Inventis Piano Plus audiometer. Broadband noise (BBN) was presented to contralateral ear at 50 dB SL (relative to noise threshold) via same ER3A insert earphones used for estimating the noise thresholds. Noise was presented 15 s before the presentation of primaries while recording in contralateral noise condition. The position of the probe was maintained throughout the testing. CAS of OAE was calculated from the difference between OAE amplitudes with noise and without the noise condition.


  Results Top


The data obtained for Quick-SIN scores, CAS of DPOAE, MLD using continuous stimuli (CMLD) and pulsating stimuli (PMLD) from both Group 1 and Group 2 were tabulated and analyzed using Statistical Package for Social Sciences (SPSS version 21.0, SPSS Inc. Chicago, ) software. Descriptive statistics was applied on the obtained data for all the parameters measured. The mean, median, and SD are shown in [Table 1].
Table 1: Mean, median and standard deviation for contralateral suppression, masking level difference using continuous stimuli, masking level difference using pulsating stimuli and quick speech-in-noise scores (dB) for both the groups

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In the above descriptive analysis, it was observed that overall CAS values were greater and Quick-SIN values were lesser in Group 1 compared to Group 2. However, there was no such trend observed between the two groups for CMLD and PMLD. CAS was higher at 1 kHz, 1.5 kHz, and 2 kHz compared to 3 kHz, 4 kHz, and 6 kHz for both musicians and nonmusicians. CMLD and PMLD were greater at 250 Hz and 500 Hz (low frequencies) compared to 1 kHz, 1.5 kHz, and 2 kHz (mid frequencies) in both the groups. Nonparametric tests were carried out for CAS, Quick-SIN, CMLD, and PMLD as Shapiro–Wilk's test did not show normality for the data obtained.

Comparison of masking level difference using continuous stimuli between and within two groups

Comparison of group within each frequency for masking level difference using continuous stimuli

The differences between the groups regarding median were observed across the frequencies selected for testing. Hence, Mann–Whitney U-test was carried out to check for significance at those frequencies. The results revealed no significant difference between the two groups across all the frequencies (P > 0.05) [Table 2].
Table 2: │z│ values and P values of Mann–Whitney U-test for masking level difference using continuous stimuli

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Comparison of frequency within each group for masking level difference using continuous stimuli

Differences across the frequencies were observed using Friedman test for Group 1 (χ2 [4] = 52.167, P < 0.01) and Group 2 (χ2 [4] = 44.252, P < 0.01). Hence, Wilcoxon signed rank test was carried out for pair-wise comparison across frequencies in both the groups. In Group 1, there was significant difference between frequency pairs: 250 Hz and 1 kHz, 250 Hz and 1.5 kHz, 250 Hz and 2 kHz, 500 Hz and 1 kHz, 500 Hz and 1.5 kHz, 500 Hz and 2 kHz, 1 kHz and 1.5 kHz, 1 kHz and 2 kHz at 0.01 level of significance, and significant difference between frequency pairs: 1.5 kHz and 2 kHz at 0.05 level of significance. In Group 2, there was significant difference between frequency pairs: 250 Hz and 1 kHz, 250 Hz and 1.5 kHz, 250 Hz and 2 kHz, 5000 Hz and 1.5 kHz, 500 Hz and 2 kHz, 1 kHz and 1.5 kHz, 1 kHz and 2 kHz at 0.01 level of significance, and significant difference between frequency pairs: 500 Hz and 1 kHz, 1.5 kHz and 2 kHz at 0.05 level of significance.

Comparison of masking level difference using pulsating stimuli between and within two groups

Comparison of groups within each frequency for masking level difference using pulsating stimuli

Differences between the groups regarding median were observed across the frequencies selected for testing. Hence, Mann–Whitney U-test was carried out to check for significance at those frequencies. The test revealed no significant difference between the two groups across the frequencies (P > 0.05) [Table 3].
Table 3: │z│ values and P values of Mann–Whitney U-test for masking level difference using pulsating stimuli

Click here to view


Comparison of frequency within each group for masking level difference using pulsating stimuli

Differences across the frequencies were observed using Friedman test for Group 1 (χ2 [4] = 48.993, P < 0.01) and Group 2 (χ2 [4] = 51.644, P < 0.01). Hence, Wilcoxon signed rank test was carried out for pairwise comparison across frequencies in both the groups. The results of pair-wise comparison revealed that there was significant difference between frequency pairs: 250 Hz and 1 kHz, 250 Hz and 1.5 kHz, 250 Hz and 2 kHz, 500 Hz and 1 kHz, 500 Hz and 1.5 kHz, 500 Hz and 2 kHz, 1 kHz and 1.5 kHz, 1 kHz and 2 kHz at 0.01 level of significance. There was a significant difference between frequency pairs: 1.5 kHz and 2 kHz at (P < 0.05). However in the case of Group 2, there was significant difference between frequency pairs: 250 Hz and 1 kHz, 250 Hz and 1.5 kHz, 250 Hz and 2 kHz, 500 Hz and 1 kHz, 500 Hz and 1.5 kHz, 500 Hz and 2 kHz, 1 kHz and 1.5 kHz, 1 kHz and 2 kHz at (P < 0.01).

Comparison of contralateral suppression between and within two groups

Comparison of groups within each frequency

The differences between the groups regarding median were observed across the frequencies selected for testing. Hence, Mann–Whitney U-test was carried out to check for significance at those frequencies. The test revealed significant difference between the two groups for all the CAS frequencies (P < 0.05), with greater suppression observed for Group 1 compared to Group 2 [Table 4].
Table 4: │z│ values and P values of Mann–Whitney U-test for contralateral suppression

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Comparison of frequency of contralateral suppression within each group

Differences between the frequencies were observed using Friedman test for Group 1 (χ2 [5] = 16.824, P < 0.01) and Group 2 (χ2 [5] = 28.924, P < 0.01). Hence, Wilcoxon signed rank test was carried out for pair-wise comparison across frequencies in both the groups. The results of pair-wise comparison revealed that there was significant difference between frequency pair 1 kHz and 4 kHz in Group 1 at 0.01 level of significance and significant difference between frequency pairs: 1 kHz and 6 kHz, 1.5 kHz and 4 kHz, 1.5 kHz and 6 kHz, 2 kHz and 3 kHz, 2 kHz and 4 kHz, 2 kHz and 6 kHz at 0.05 level of significance. However, for Group 2 there was a significant difference between frequency pairs: 1 kHz and 6 kHz, 1.5 kHz and 6 kHz, 2 kHz and 6 kHz, 3 kHz and 6 kHz, 4 kHz and 6 kHz at (P < 0.01).

Comparison of quick speech-in-noise between the two groups

Mann–Whitney U-test was carried out to compare the two groups for Quick-SIN. The test revealed a significant difference between the two groups (/z/ = 2.126, P < 0.05). The scores obtained were significantly better for Group 1 than Group 2.

Comparison between masking level difference using continuous stimuli and masking level difference using pulsating stimuli

Wilcoxon signed ranks test was carried out to compare between CMLD and PMLD. The test revealed a significant difference only at 2 kHz in Group 1 (/z/ = 2.230, P < 0.05), with better scores for PMLD. However, there was no significant difference in Group 2.

Correlation across contralateral suppression of distortion product otoacoustic emission, masking level difference using continuous stimuli and quick speech-in-noise for Group 1 and Group 2

Spearman's correlation was done to investigate the correlation across CAS of DPOAE, CMLD and Quick-SIN in both the groups. Results revealed significant negative correlation between CMLD at 500 Hz and CAS at 4 kHz in Group 1 (ρ = −0.761, P < 0.05). However, there was no significant correlation (P > 0.05) between other parameters, that is, across CAS and CMLD at other different frequencies and Quick-SIN in them.

In Group 2, significant positive correlation was observed between CMLD at 2 kHz and CAS at 3 kHz (ρ = 0.526, P < 0.05), CMLD at 500 Hz and CAS at 4 kHz (ρ = 0.525, P < 0.05). Furthermore, significant negative correlation was observed between CMLD at 1.5 kHz and CAS at 1.5 kHz (ρ = −0.743, P < 0.05). However, there was no significant correlation (P > 0.05) between other parameters, that is, between CAS and CMLD at other different frequencies and Quick-SIN in them.

Correlation across contralateral suppression of distortion product otoacoustic emission, masking level difference using pulsating stimuli and quick speech-in-noise for Group 1 and Group 2

Spearman's correlation was done to investigate the correlation across CAS of DPOAE, PMLD and Quick-SIN in both the groups. Results revealed significant positive correlation between PMLD at 1.5 kHz and CAS at 3 kHz in Group 1 (ρ = −0.661, P < 0.05). However, there was no significant correlation (P > 0.05) between other parameters, that is, across CAS and CMLD at other different frequencies and Quick-SIN in them.

In Group 2, there was no significant correlation (P > 0.05) between the different parameters, such as CAS, PMLD at different frequencies and Quick-SIN.


  Discussion Top


Results revealed that Group 1 outperformed Group 2 in CAS of DPOAEs and Quick-SIN. However, no significant difference was seen in the performance in CMLD and PMLD between the two groups.

Masking level difference using continuous stimuli and masking level difference using pulsating stimuli

Comparing the results between CMLD and PMLD, there was no significant difference obtained between Group 1 and Group 2 irrespective of the frequencies. These results reveal that MLD (continuous and pulsating) would not be a sensitive tool to quantify the effect of musical training. There has been literature reporting that MLD at low frequencies is better when compared to high frequencies.[15] A similar trend was also observed in the current study were the responses were better at the lower frequencies. However, between the two groups there was no significant at 250 Hz and 500 Hz in CMLD and PMLD.

Contralateral acoustic suppression of distortion product otoacoustic emissions

The results of comparing CAS of DPOAEs revealed significant greater suppression of DPOAEs in Group 1 than Group 2 across the frequencies tested. This is in agreement with earlier studies reported in the literature.[3],[4],[5],[6],[16] Micheyl et al.[3] that enhanced activity at higher centers would enhance MOC activity in musicians relative to nonmusicians, this in turn would result in overall greater amplitude reduction over different ipsilateral stimulus intensities. Brashears et al.[5] found a greater amount of DPOAE suppression with the binaural suppressor in musicians relative to nonmusicians and this was attributed to the central auditory pathway strengthening as a result of the musical training.

CAS of DPOAEs were measured and compared across the frequencies. The lesser amount of suppression at high frequencies are in agreement with the studies reported in literature.[17],[18],[19] Moulin et al.[20] found lesser slope in the DPOAE amplitude reduction with the increment in contralateral noise, as the frequency was increased. This frequency difference in suppression was attributed to unequal firings by BBN in the efferent fibers across frequencies. Studies reported highest suppressive effects to be seen at mid frequencies (1 kHz and 2 kHz), as the uncrossed MOC efferent fibers innervate majorly to the center of the cochlea.[21]

Quick speech-in-noise

SIN abilities was found to be significantly greater in Group 1 compared to Group 2. Similar findings have been reported in literature.[2],[7],[22],[23] Superior performance was reported in younger musicians [2] and older musicians [22] relative to nonmusicians in working memory and Quick-SIN. Quick-SIN contains semantically less predictable and lengthier sentences and hence it requires good working memory. Hence, they attributed the better performance in Quick-SIN to the superior working memory abilities in musicians.[2],[22] One of the major functions of the efferent system is speech perception in noise.[24] Hence, the stronger efferent system in the Group 1 could have resulted in better speech perception in noise.

Comparison between masking level difference using continuous stimuli and masking level difference using pulsating stimuli

CMLD and PMLD scores were compared within Group 1 and Group 2. PMLD was significantly greater when compared to CMLD at 2 kHz alone for Group 1. However, such a difference was not seen in Group 2. In Group 1, the pulsating tone cued for better perception resulting in better MLD when compared to continuous tone, especially at 2 kHz. However, the results were not similar at low frequencies as MLD reaches ceiling effect at low frequencies. Hence, the effect of musical training could be seen to certain extent using PMLD than when compared to CMLD.

Correlation of contralateral suppression of distortion product otoacoustic emission and quick speech-in-noise with masking level difference using continuous stimuli and masking level difference using pulsating stimuli

The correlations across CAS of DPOAE, CMLD and Quick-SIN in both the groups were studied. In Group 1, there was a significant negative correlation between CMLD at 500 Hz and CAS at 4 kHz. However, there was no correlation between other parameters. In Group 2, there was a significant positive correlation between CMLD at 2 kHz and CAS at 3 kHz, CMLD at 500 Hz and CAS at 4 kHz and negative correlation between CMLD at 1.5 kHz and CAS at 1.5 kHz. However, there was no correlation between other parameters. The correlations across CAS of DPOAE, PMLD and Quick-SIN in both the groups were studied. In Group 1, there was a significant positive correlation between PMLD at 1.5 kHz and CAS at 3 kHz in musicians. However, there was no significant correlation between other parameters. In Group 2, there was no significant correlation between different parameters.

The variations observed could be attributed to heterogeneity seen within the two groups of participants. Within Group 1, the variability seen could be in terms of type of musical training (vocal or instrumental), duration of musical training, age at which the training started. Within Group 2, the variability seen could be in terms of the innateness of musicality. Since the correlation was observed between few of the parameters in both the groups, it is not possible to make any conclusions regarding the correlation across CAS of DPOAE, CMLD, and Quick-SIN. The addition of more number of participants into the research probably may help in drawing better conclusions about the correlation between the tests.


  Conclusion Top


The present study suggests that CAS of OAEs and Quick-SIN can be used to quantify the effectiveness of musical training. It can also be inferred that musical training enables strengthening of afferent and efferent pathways. This facilitates musicians to have enhanced speech perception abilities in the presence of background noise.

Acknowledgments

The authors would like to thank the Director, All India Institute of Speech and Hearing, Mysuru, Karnataka, India for granting permission to carry out the study and the participants for their cooperation.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

 
  References Top

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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4]



 

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