Development of Novel Musical Stimuli to Investigate the Perception of Musical Emotions in Individuals With Hearing Loss

BACKGROUND: Many studies have examined the perception of musical emotion using excerpts from familiar music that includes highly expressed emotions to classify emotional choices. However, using familiar music to study musical emotions in people with acquired hearing loss could produce ambiguous results as to whether the emotional perception is due to previous experiences or listening to the current musical stimuli. To overcome this limitation, we developed new musical stimuli to study emotional perception without the effects of episodic memory. METHODS: A musician was instructed to compose five melodies with evenly distributed pitches around 1 kHz. The melodies were created to express the emotions of happy, sad, angry, tender, and neutral. To evaluate whether these melodies expressed the intended emotions, two methods were applied. First, we classified the expressed emotions of melodies with selected musical features from 60 features using genetic algorithm-based k-nearest neighbors. Second, forty-four people with normal hearing participated in an online survey regarding the emotional perception of music based on dimensional and discrete approaches to evaluate the musical stimuli set. RESULTS: Twenty-four selected musical features produced classification for intended emotions with an accuracy of 76%. The results of the online survey in the normal hearing (NH) group showed that the intended emotions were selected significantly more often than the others. K-means clustering analysis revealed that melodies with arousal and valence ratings corresponded to representative quadrants of interest. Additionally, the applicability of the stimuli was tested in 4 individuals with high-frequency hearing loss. CONCLUSION: By applying the individuals with NH, the musical stimuli were shown to classify emotions with high accuracy, as expressed. These results confirm that the set of musical stimuli can be used to study the perceived emotion in music, demonstrating the validity of the musical stimuli, independent of innate musical bias such as due to episodic memory. Furthermore, musical stimuli could be helpful for further studying perceived musical emotion in people with hearing loss because of the controlled pitch for each emotion.