*4.1.3 Click-to-music loudness ratio measurements*

To investigate the extent to which the reduction of the sound masking effect in binaural enabled musicians to monitor less synchronization cues, for each of his three case studies15, Menon [9] compared the click-to-music (CMR) loudness ratio between the headphone mix recordings of the takes using his ABH and those using the traditional stereo monitoring system of the studio. For each of the takes recorded with the ABH, he copied the musicians' KV interface settings into a "second user," so that he could print the monitoring mix that featured the binauralization of the four headphone-mounted microphones and the synchronization cues. For each of the takes recorded with the stereo headphones, he captured the signal from the headphone output of the Aviom personal monitor mixer by using a stereo jack into two unbalanced jack adapters and two Direct Input (DI) boxes. Then, because each monitoring mix replica would include a few seconds of synchronization cues before the beginning of the music performance, he could normalize the loudness of each replica with the synchronization cues as a reference. This data acquisition procedure enabled the visualization of the CMR throughout and across takes.

### **4.2 Experimental findings**

For the seven case studies during which performers compared binaural and stereo headphones, all performers favored the binaural over the stereo condition. In the following sections, we detail comparison findings for the main criteria that emerged from our analysis of performers' comments and take choices, namely Listening comfort; Perceived realism; and Musical expression and creativity.

For the symphonic jazz ensemble recording session, the comparison could not be conducted as planned due to several challenges that highlighted the limitation of the BMH [7]. This large ensemble combined orchestral and big band instruments with electric guitars and keyboards that were not amplified in the room, as well as drums that were semi-isolated in the room. Consequently, the electric guitars, keyboards, and the double-bass' quiet acoustic sound were not captured by the main 5-microphone array so they could not be homogeneously integrated into the auditory scene. Also, the main array captured a lot of drum leakage, which damages the intelligibility of the auditory scene. Moreover, the

<sup>15</sup> Menon [9] conducted a fourth case study with a classical pianist who tested the ABH and compared it to stereo headphones to monitor a metronome while performing Beethoven's Piano Sonata No. 2, Op. 57. Because this piece would not be performed with a metronome in professional situations, we excluded this fourth study from this chapter.

complexity of the situation generated communication challenges between the electric instrument players, the sound engineer, and the conductor, therefore the conductor did not feel comfortable enough to use the BHT for the session. In the discussion, we provide ideas to overcome the BHT limitations for conducting large ensembles that blend different types of instruments in large acoustics.

#### *4.2.1 Listening comfort*

All eleven performers who participated in comparative studies in the recording studio preferred the auditory feedback quality of their own sound production in the binaural conditions. In particular, two improvisers who tested the BMR and all performers who tested the ABH reported having more control of their own instruments. For instance, the world music performer kept both earcups in the binaural condition but removed one earcup to control his voice in relation to the room acoustics in the stereo condition. Also, the double bass player of the jazz trio perceived a more realistic "physical-auditory contact" with his instrument in the binaural condition.

The conductor and seven instrumentalists expressed being more comfortable while performing in the binaural condition. In particular, whereas Maestro Petitgirard was a bit reluctant to try the BHT in the beginning, he mentioned feeling comfortable with it as soon as he started using it. Also, two out of the four performers who tested the ABH stated that they were able to forget about the device while monitoring in binaural. Furthermore, three out of the seven performers who tested the BMR reported that the binaural condition was less tiring in comparison with the stereo condition. Only the world music performer was disturbed during the first hour by this new kind of monitoring.

All performers perceived better sound quality in the binaural condition that they described as more natural than stereo in terms of spatial realism and audio clarity. With the BMR, all performers perceived the binaural mix as more intelligible, since they could better differentiate the details of the different instruments. In this view, free improvisers and jazz musicians reported "not having to force" to hear what they needed to react to their bandmates' musical gestures. They could appreciate more subtleties in their playing, for example, the sounds of the fingers on the double bass and soft percussions, and the drummer said that the sound was more "accurate to what they would hear in their daily practice." Also, the free improvisers who used the BMR and Maestro Petitgirard who used the BHT perceived more depth in the binaural mix compared to the stereo mix.

#### *4.2.2 Perceived realism*

Across the seven comparison studies, performers expressed that binaural monitoring was more realistic. However, the meaning of *realism* varied according to the type of augmentation that was used in the different studies. Regarding the two AAR systems, realism implied that the binaural rendering of the music signal was close to the real auditory environment in terms of source spatialization, room acoustics, and timbre quality. In contrast, regarding the BMR solution that is AMR, by realism performers meant that they could recreate familiar auditory situations in their mind, for example, to "be in the performance" and to connect with other players and their own instrument like in rehearsal. In the next paragraph, we illustrate these two meanings of realism with test observations.

When first trying the BHT, Maestro Petitgirard thought that he was only hearing the click track, and Soudoplatoff had to convince him that the orchestra

### *Binaural Headphone Monitoring to Enhance Musicians' Immersion in Performance DOI: http://dx.doi.org/10.5772/intechopen.104845*

was also rendered in the headphone mix by muting the microphones for a few seconds. Similarly, all performers who experimented with the ABH mentioned that they perceived a more realistic spatial image in comparison with stereo monitors. Beyond the basic acknowledgment of the spatial authenticity that the ABH facilitated, performers commented explicitly on the efficacy of this enhanced acoustic realism. For instance, the pianist who performed the electroacoustic piece stated, "I felt myself making decisions in real-time, reacting to my own emotions and improvising some aspects of interpretation, whereas with the traditional headphones, I found my performance becoming stagnant." As for the AMR system, since 3D audio cues did not match the real auditory scene of the studio, realism was about the sound quality of recreated acoustics and the convincing spatialization of 3D audio cues. This led the world music performer to report that he "had the impression that the music was real around him." Moreover, two of the free improvisers had the impression that their bandmembers were next to them although they were in separated rooms. In particular, the clarinetist said: "It recreated a second room where we were all present in my head."
