PROCEEDINGS of the23rd International Congress on Acoustics
9 to 13 September 2019 in Aachen, Germany

Dicriminability of high-resolution audio with regard to thequantization accuracy'
Masanobu MIURA
Kunitachi College of Music, JapanABSTRACT
The high-resolution audio has been popular for commercially-sold music delivery services. The
high-resolution audio is characterized in both the over 20Hz components and high-quantization accuracy.
This presentation focuses on the quantization accuracy in terms of the discriminability of the difference onquantization accuracy. In particular, here employs 24 bits and 16 bits format’s audio as experimental stimuli,
where the ones of 16 bits are created by conducting downbit-processing for commercially sold 24 bits audio.
Three methods of downbit-processing are employed. 10 university students were asked to listen to the audio
and to answer the format, as 24 or 16. The stimuli are simultaneously presented to listeners throughheadphones. Then the listeners were asked to answer the sound image localization. This method is newly
employed here. The method has an advantage that listeners are possible to compare the sound simultaneously
and to answer the sound image locations, which is thought as easier to rate than to the conventional listening
experiment, just presenting each by each. The experimental result shows significant difference on thediscrimination on the difference of audio format. The factor why people are possible to discriminate will be
discussed on the conference venue.
Keywords: High-resolution Audio, Discriminability, 24bit, 16bit

1. INTRODUCTION
The high-resolution audio has been popular for industrial music commerce. The high -resolution
audio has finer resolution on either or both time and amplitude. Here focuses on the resolution fromthe quantization. The discriminability of the resolution on quantization is discussed here. On theconventional method ABX method, subjects are asked to rate two distinct sounds that are presented
each by each. In case of using lowbit and highbit sound sources, in particular 16 and 24 bit, subjects
feel usually the difficulty of the difference between them, since the difference of resolution of thesound is perceived as weaker than the consistent context of the music. To cope with the problem, weproposed a method to use sound localization using headphone presentation, where the 16 or 24 bitsound on consistent context is presented either left or right channel. The listeners are asked to rate
the sound image localization. If the sound image is localized neither left nor right side, the subjects
are assumed that he/she can perceive the difference of 24 and 16 bit. On this report, we examine thepossibility of the sound image localization when using 16 and 24 bit audio on each ear side forconsistent music context.

2. DOWNBIT PROCESSING
The stimuli of the sound image localization are the modified sound sources of originalcommercially sold music. The music of the original sound source is a performance of wind orchestra,
played by the Japanese professional wind-orchestral band. Original music’s format is 48000Hz with
24bit. Three types of downbit processing are conducted for the original music. The three methods
consist of three rounding from 24 bit to 16 bit by 1) up, 2) down, or 3) nearest step on 16 bit. Figs.1-3
shows each of the processings.

3. LISTENING EXPERIMENT
A listening experiment is conducted where four types of wind orchestra music are employed. Oneach of the stimuli, left or right channel is either 16 or 24 bit, labelled as (16-16, 16-24, 24-16,24-24).
Length of each stimuli is approximately 30 seconds. Ten students (L1 to L10 ) belonging to engineering
university participated in this test. They were asked to rate the consistency of sound image localizationon the conductive two music. Results are shown on figure 2, where the correct answer rate is 44.38%,

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being higher significantly ( p<.05, chi-square test).

Fig.1 Rounding to upper stepFig.2 Rounding to lower stepFig.3 Rounding to nearest stepb)

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(a) Result for the rounding 2).

(b) Result for the rounding 3).

Fig.4 Results of the listening experiment.

4. DISCUSSION
As my colleagues reported that when using the rounding 1) and when using amateur musician’s
students[1], the average of correct answer ratio raises to 46.8% and five out of the ten musicalstudents are significantly possible to answer correctly the sound image localization. Along with theresults mentioned above, the possibility that people can discriminate the difference of sounds
between 24 and 16 bit by listening experiments. I believe the result may be the new approach todiscriminate two distinct sounds.

5. CONCLUSIONS
Here a new methodology using the sound-image localization to discriminate the difference of 24 bit
and 16 bit sounds is presented. A possibility that people can discr iminate the 24 and 16 bit sounds isintroduced.

ACKNOWLEDGEMENTS
We express our sincere thanks to Akio Suguro, for his support to achieve experimental results fromhis master thesis of Hachinohe Institute of Technology, Japan.

REFERENCES
1. Akio Suguro, Masanobu Miura, "Quality discrimination on high-resolution audio with difference ofquantization accuracy by sound-image localization", 2018 AES International Conference on Spatial
Reproduction (2018).

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