A qualitative, thematic analysis of listeners’ feedback revealed that the noise artefacts that produced the ACER technique are different from those of comparator codecs, reflecting its novel approach. However, in terms of participants’ perceptions of the stereo field, all formats under test performed as well as each other, with no statistically significant differences. Results show that participants reported no perceived differences between the uncompressed, MP3, AAC, ACER high quality, and ACER medium quality compressed audio in terms of noise and distortions but that the ACER low quality format was perceived as being of lower quality. The aim was to determine the efficacy of the ACER codec, in terms of perceptible noise and spatial distortion artefacts, against de facto standards for audio data compression and an uncompressed reference. In this paper, we present a double-blind listening test that was conducted with a range of listeners (N=100). However, previous work did not evaluate ACER using subjective listening tests, leaving a gap to demonstrate its applicability under human audio perception tests. Our previous research presented a novel codec named ACER (Audio Compression Exploiting Repetition), which achieves data reduction by exploiting irrelevancy and redundancy in musical structure whilst generally maintaining acceptable levels of noise and distortion in objective evaluations. Over all significant difference between the results’ distribution musical excerpts, listeners significantly preferred amongst the five musical excerpts ( χ 2 (4)=22.52,Īudio data compression has revolutionised the way in which the music industry and musicians sell and distribute their products. The chi-square test revealed a and they preferred the lower quality version. Under 4 6%, the results indicate that preferred, and the number of times the lower quality listeners could discriminate between the two versions version was preferred). Performance hypothesis, we compared the distribution of preferences over 54% indicates that listeners could discriminate using the chi-square statistic on occurrences (counting between the two versions and that they preferred the the number of times the higher quality version was higher quality. To test this they cannot discriminate between the two. Using the binomial test, performance ranging between 46 and 54% is not significant (p>0.05), Our next research question was whether listeners’ meaning that listeners had no significant preference for sensitivity to these audible artifacts is a function of one version over the other, which strongly suggests that musical genre and listeners’ expertise. Effect of musical genre and expertise and all excerpts). preferred the higher quality version, grouped by comparison pair (results collapsed over all pants 3.2, 3.2. Figure 1 demonstrate that mp3 compression does introduce presents the results as percentage of times participants audible artifacts. These overall results the higher quality version 68% of times. Overall preference higher quality version, except for the comparison between 320 and 256 kbits/s where the results did not Over all pairwise comparisons, participants preferred reach statistical significance. RESULTS comparisons amongst mp3 files with different levels of compression, listeners always significantly preferred the 3.1. Results collapsed over all participants and musical excerpts, grouped by comparison pair: significant preferences are displayed in grey, non-significant in white.
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