EDICTO DE EMPLAZAMIENTO
A: RICARDO VERA GARCIA Presente
The experimental procedure and design, as well as the stages of execution of the experiment are presented below.
3.4.1
Audio Track Development
The tracks were: Another Brick in the Wall Pt.2 by Pink Floyd1off The Wall album
and the Violin Concerto No.3 by Camille Saint-Saens2. These two tracks were
chosen to represent the two genre extremes of popular rock and classical music. The initial tracks selected included:
• Pink Floyd: Another Brick in the Wall Pt.2 • Eric Clapton: Layla, Unplugged
• Mark Salona: Rafael
• Wolfgang Amadeus Mozart: Piano Sonata No.11
1 According to Urick (2016), The Wall album was released in 1979 and was deemed one of the more creative albums in rock music
2 MusOpen (nd) highlights that Saint-Saens composed his final Violin Concerto with a sense of subtle impressionism in 1880.
Camille Saint-Saens was chosen over Rafael and the Piano Sonata because it was previously recorded by Sun Studios as part of Stellenbosch University in ac- cordance with the -23 LUFS. Another Brick in the Wall Pt.2 contained a good va- riety of both vocals and instrumental music which outweighed the solo voice and accompaniment of Layla.
Both the Violin Concerto No.3 and Another Brick in the Wall Pt.2 had 30 second segments selected as it was felt that a 30 second window would be long enough for a listener to make their loudness decision. The time window was tested briefly by the researcher with 1 minute and 45 second segments respectively, but was felt to be too long as the loudness indication was almost instantaneous.
3.4.1.1 Audio Processing of Tracks
The musical tracks were played to the participants as the artist/composer intended. This means that the tracks did not undergo any dynamic compression. The only processing Pink Floyd and Saint-Saens underwent was in accordance with the EBU R128, to ensure uniformity of the output levels to -23 LUFS.
This procedure was carried out in ProTools using the WLM plugin (WavesAudio, 2016) with the newly processed files analysed further with the R128x (Github, 2016), ensuring the Integrated loudness outputs for both tracks was set to -23 LUFS. Once the tracks had been aligned in accordance with the EBU R128, both tracks were checked again using the R128x by Github (2016). The difference in musical dynamic range is explained in LU, whereby the Pink Floyd has 2 LU, compared to the 14 LU of the Saint-Saens. This means that the Pink Floyd track was recorded and produced with more dynamic compression, whereas the Saint-Saens has no added destructive dynamic compression.
The method of audio processing through the WLM plugin was chosen over the Auphonic batch processor (Auphonic, 2016) as a more trusted source within ProTools was deemed the better option. Furthermore, the MLoudnessAnalyzer (MeldaProduction, 2009) for Logic Pro was discarded in favour of the R128x anal- ysis software. This is because the MLoudnessAnalyzer presented limitations due to it being a trial version.
3.4.1.2 Background Noise
In addition to the two selected musical tracks, an hour long wave file of Pink Noise was generated using Tone Generator software (NCH, nd). The duration of the Pink Noise track was generated long enough to ensure that the track could play continuously without abruptly stopping midway through a subject’s participation.
3.4.2
Research Set-up
This section will detail the experimental setup and the full procedure, from subject participation through to the conversion of linear data into dBA readings.
3.4.2.1 Research Equipment
The software preparation prior to the undertaking of the experiment, involved the choice of analysis software and microphone. The analysis was to be done using an iPad 2.0 equipped with a Thomann Mic-Wi436 (Thomann, 2016) and the Analyzer software from DSP Mobile (DSP-Mobile, 2012) installed. This analysis software was chosen over the initial Sound Meter by Faber Acoustical (FaberAcoustical, 2016) due to the extension support for the Mic Wi436, as well as a visual display graph instead of a simple decibel meter. The iPad, coupled with the Mic-Wi436 and DSP Mobile Analyzer were utilised during the post-experimental stage to convert the linear scale of the Renault’s radio volume control to a decibel scale.
The Apple iOS 6 update from 2012 allows developers to bypass the high-pass filter limitation of previous iPhones. This enables Apple iPhones to connect with external microphones such as the Mic Wi436 which comply with the IEC 61672 Class 2 sound level meter standard (Kardous & Shaw, 2015:12).
Finally, the researcher tested both the musical tracks through Audacity and through an auxiliary cable into the car’s stereo system ensuring that the tracks played without any disruptions. The microphone and DSP Mobile Analyzer soft- ware were also tested in detail to ensure accurate calibration between the sensi- tivity of the microphone and the DSP Mobile Analyzer software.
The full list of equipment used during the experiment is listed as follows: • Radio Shack Digital Sound Level Meter
• MacBookPro with Audacity • MacBookPro Charger • iPhone to play Pink Noise
• iPad 2.0 with the DSP Mobile Analyzer installed • Two Yamaha MSR100 Loudspeakers
• XLR Cables • DI Box
• Jack to 1/4 inch Jack for iPhone to DI • Multi-plug
• Extension Power Cable
The vehicle and speakers were set up in as shown in Appendix E, with each of the speakers placed on the ground next to the front wheel and front doors at a 45 degree angle. The speakers would generate pink noise to give the simula- tion of the the car being in city-centre traffic. The windows of the front seats on both the passenger and driver’s sides were cracked open for air and the car en- gine was switched off during the time of the recording. This would allow for the right amount of pink noise to bleed into the vehicle. The Radio Shack (RadioShack, 2011:1) digital sound level meter was used alongside the pink noise from the speak- ers to calibrate the interior noise level. This was set to 60 dBA, measured with a slow response time. This gave the reference level within the vehicle prior to any music tracks being played.
3.4.2.2 Research Venue
The experiment was setup behind the Endler Hall of the Conservatorium at Stel- lenbosch University. This area was large enough to accommodate the car as well as being easily accessible for the participants. Moreover, the location was secluded from the main street, allowing for the background noise variable to better con- trolled. The vehicle was parked close enough to the Conservatorium’s backdoor allowing for easy access to external power to supply the equipment.
3.4.2.3 Experimental Set-up
The experimental set-up is displayed in Appendix E. The speakers were connected to one another as well as to the multi-adapter for power. The speaker next to the passenger door was connected to the DI box and onward to the iPhone as this would provide the source of the Pink Noise. The researcher was seated in the pas- senger seat of the car, holding the iPhone and the necessary cables were running through a crack in the car window to power the MacBookPro on the researcher’s lap. The MacBookPro was unplugged from the power source at the start of each participation as the power source caused interference with the car’s stereo system. 3.4.2.4 Questionnaire Design and Completion
Prior to subjects participating in the experimental procedure, they were asked per- sonally by the researcher if there were any questions as to what was expected of them or what was to be presented. In this way, each participant knew what to expect during the experimental phase, allowing for their comfortable input and relaxed loudness adjustment.
For each participant, the researcher would invite them to be seated in the driver’s seat before prompting them with the Declaration (Appendix D) and Ques- tionnaire (Appendix A). The declaration would be read through with the partic- ipant to ensure they were satisfied with what was expected, as well as to clar- ify any questions the participant had regarding the experiment. Furthermore, the
questionnaire was filled out under the supervision of the researcher to ensure that each question was understood.
The questionnaire was designed to build a demographic of the subjects par- taking in this study. The questionnaire can be seen in Appendix A, with a full motivation for the choice of each question in Appendix B. From a psychological point, questions 2 and 3 focussed on why some individuals prefer music louder or softer based on their exposure to music. This issue was briefly addressed, but the role of psychological attributes to loudness preferences was beyond the scope of this study.
After the declaration was signed and the questionnaire completed, the pink noise was turned on and the participant listened to each track. The Pink Floyd track was played to each participant first, followed by the Saint-Saens. Once par- ticipants verbally indicated that they were happy with their loudness selection, the procedure was terminated. The subject was then thanked for his/her participation. It was decided that a pilot study was not necessary prior to the undertaking of the full experiment. The two musical tracks were pre-selected from laboratory tests whilst the rest of the research design is considered to be easily understood. 3.4.2.5 Data Recording
Once all subjects had participated, their selections were still in a linear format from the volume control on the car’s dashboard. For example: Another Brick in the Wall Pt.2 played at volume number 25. In this linear format, the results show a variation across loudness levels, but cannot be used for comparison and there- fore required conversion into decibels. This conversion procedure included the re- searcher seated in the driver’s seat listening to each 30 second track and analysing the decibel peaks generated using the Mic Wi436 on the DSP Mobile Analyzer.
Even though a few participants had a cross over loudness preference, the linear value was run only once. This means that the linear values were run from 20 - 32 for the Pink Floyd track and from 17 - 32 for the Camille Saint-Saens track. The peak value for each 30 second segment was recorded as well as a CSV file generated for the Leqover the entire segment of each reading. The DSP Mobile Analyzer was
set with a slow response time, Leqand 1/3 octave band for each generated CSV file.
This data will be presented in the next chapter.
3.4.3
Ethical Considerations
Prior to conducting the experiment, ethical clearance was obtained from the Uni- versity’s research ethics committee.
The investigation incorporated the participation of human subjects for the evaluation of perceived changes in loudness between popular and classical mu- sic tracks. Each subject was presented with two forms outlining the purpose of the research as displayed in Appendix C, as well as the written consent for their participation as shown in Appendix D. Upon undertaking the experiment, the par-
ticipants were asked to complete a questionnaire under the supervision of the re- searcher. Anonymity of the participants was ensured through the use of partici- pant numbers instead of their names.
3.4.4
Budget
The researcher had access to literature, sound equipment and hardware needed for the purpose of this research. The software used in the experimental phase was bought by the researcher, amounting to R345 and was paid as a personal expense. The investigation was conducted using sound equipment from the Stellenbosch University’s Studio, at an outdoor location large enough to work with a passen- ger car. The researcher accepted the responsibility of costs associated with the postgraduate study in his personal capacity.
Chapter 4
Results and Analysis
In this chapter the results obtained from the experimental procedure will be visu- ally presented.