a r t i c l e i n f o

Article history:

Received 7 December 2022

Received in revised form 2 March 2023 Accepted 31 March 2023

Available online 2 May 2023

Keywords:

Room acoustics

Musical clarity

C80

Listening test

Stimuli

Perception

a b s t r a c t

C80 is an acoustic parameter that evaluates the influence of the room on the perception of musical clarity. Numerous studies have been carried out to determine its just noticeable difference (JND). In those evaluations different musical pieces have been used, and different results have been observed depending on the pieces. In some studies, the difference was considered significant, while in others it was not. The lack of agreement on the effect that the musical piece has on the assessment of C80 is the main motivation for this research.

A listening test was carried out in order to assess whether the musical motif has an influence on the perceived musical clarity of a room. In studying this influence, it was necessary to use musical motifs with very different characteristics. A total of five pieces were selected: one liturgical vocal piece, one fast tempo solo piece, one slow tempo solo piece and two orchestral pieces, one fast and one slow. These motifs were used to create the stimuli used in the test by convolution with impulse responses of rooms with different C80 levels. Impulse responses were obtained by modifying the virtual models of three rooms. Eighteen impulse responses were used with C80 levels between 5.90 and 6.75 dB. The listening test was carried out by 36 participants with varying degrees of musical training.

It was intended to answer two different questions. Firstly, whether the participants were able to percieve C80 changes in all musical motifs. And secondly, whether the musical motif was a significant factor when assessing the C80 level of a stimulus. The first question was assessed using regression analysis and Cochran-Mantel–Haenszel (CMH) analysis. It could be observed that the participants were able to notice changes in the C80 level for the solo instrument pieces and the vocal motif. For the orchestral pieces, on the other hand, this differentiation ability could not be seen. To assess whether the motif is a significant factor in evaluating a C80 level, a CMH analysis was performed. The results indicate that, for all rooms, musical motifs are a significant factor in assessing the clarity of a venue. Consequently, it can be stated that the musical motif used for the evaluation of the clarity of a room by means of a listening test has an influence on the results obtained.

2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

1. Introduction

It has already been a century since Wallace C. Sabine described the measurement of reverberation time as a predictor of the acoustic quality of a room [1]. During the second half of the twentieth century several additional descriptors have been developed to describe different acoustic features of a venue, such as intelligibility [2] and spatial impression [3]. This development was based on the realization that reverberation time alone is insufficient to describe how an acoustic environment is perceived. The relation-

Corresponding author.

E-mail address: m.larrosa@upm.es (M. Larrosa-Navarro).

ship between room acoustics indicators and listeners’ subjective impression of a space has become the focus of a lot of studies in the field of room acoustics [4–6].

One of the many parameters used to characterize acoustic environments is the clarity index, C80. This descriptor is used to quantify the perception of musical clarity. It is defined as the logarithmic ratio of early sound energy, arriving in the first 80 ms, to late sound energy, arriving after 80 ms [7].