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19th INTERNATIONAL CONGRESS ON ACOUSTICS MADRID, 2-7 SEPTEMBER 2007

ASSESSMENT OF MUSICAL INSTRUMENT PERFORMANCES FOR PRACTICE ROOMS BY MUSICIANS

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Saher, Konca ; Özis, Feridun ; Rindel, Jens Holger 1 Delft University of Technology; Berlageweg 1, CR 2628, Delft, the Netherlands; [email protected] 2 Dokuz Eylul University, Fine Arts Faculty, Musicology Department, Izmir, Turkey, [email protected] 3

Ørsted-DTU, Acoustics Technology,Ørsted Plads, Bld 352 Technical University of Denmark, DK-2800 Kgs. Lyngby; [email protected]

ABSTRACT This paper continues to discuss how a specific musical instrument impacts the design of practice rooms. In the previous paper six instruments (violin, clarinet, trumpet, xylophone, piano, and guitar) and a choir performance are assessed. The reverberation time (RT) is a starting acoustical consideration and the floor area is a starting architectural consideration. The rooms are simulated with the architectural variables. The anechoic recordings are used to prepare auralizations of each instrument and the choir performance for each separate room design. However, ordinary people are asked to select for the best rooms to listen/experience the rooms. In this paper, the same listening tests were done to investigate the ‘best’ room preference of the professional musicians to practice. Then the musicians were also asked for their listening preference. The appropriate reverberation time and the most preferable rooms are demonstrated. One of the results of this experiment is that musicians make a clear distinction between the rooms for practicing and rooms for listening. For the practice low RT (0.45-0.9 sec) is preferred for violin, clarinet, trumpet, while high RT is preferred for choir (2-2.5 sec). For the listening experience for most of the instruments mid RT values (1.3-1.6 sec) is preferred. For all calculations and the auralizations, a computational model is used: ODEON 7.0.

INTRODUCTION Learning music needs private practicing as well as group practicing. Therefore, spaces of different sizes and different properties are required to accommodate in musical education facilities. In literature some guidelines for the design of the practice rooms, in particular small practice rooms, could be found [e.g 1,2] However, each musical instrument has its own special frequency range and sound power level. When designing a conservatory practice room it is crucial to design rooms dedicated for certain instruments. These rooms are supposed to provide an environment for musicians and vocalists to assess and improve their performance. In the preceding paper [3] the most appropriate room type for the practice of six instruments (violin, clarinet, trumpet, xylophone, piano, and guitar) and a choir performance is assessed. The range of reverberation time (RT) is chosen as the acoustical criteria and the floor area is chosen as the architectural criteria. Six different room models have been prepared and the anechoic recordings of six discrete instruments have been convolved with the room impulses of these models. The prepared auralizations of each instrument and the choir for six different room models have been used to prepare the listening tests. People are asked for their preference of best and worst rooms for to experience/listen the instruments. The results showed that for the xylophone, choir and piano people prefer high reverberation time between 2.0-2.5 seconds. This reverberation time range could be achieved with a floor 2 area of 80 m . For the guitar the people prefer dry rooms (Reverberation between 0.45-0.9 is enough). The preferences vary among people for clarinet, trumpet and violin. According to the 2 listening experiments done in this paper [3], for guitar 8m rom with a low ceiling, for trumpet,

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violin and clarinet a 25 m room, for xylophone, piano and choir a 80m room with high ceiling would be the best room. However, these listening tests were done with nine people who are not professionals. This paper repeats the same listening tests with professional musicians. However, since musicians claimed that they have different perception for the best room for an instrument when practicing and when listening the performance of the instrument the questionnaires are designed in two steps. The musicians of each instrument are particularly asked to select ‘the best’ room for practicing. Then musicians are asked for the ‘best’ room for the listening experience of the rooms. Therefore, the possible preference differences of musicians for ‘practicing the instrument’ and ‘listening the instrument’ is also investigated in this paper.

COMPUTER MODEL Architectural Model The preparation of the computer model has been made based on the information from the literature and some practical survey. The floor area has been chosen as the starting architectural criteria. ‘Planning Guide for Secondary School Music Facilities, Wenger Corp’ [2] provides some practice room guidelines. (See Table 1)

Table I.- Practice room guidelines. (Adapted from ‘Planning Guide for Secondary School Music Facilities, Wenger Corp’ [2]) Room Small Practice Keyboard Small Group Medium Group Ensemble Practice

Purpose Individual practice Private lessons, keyboard practice Small group practice Medium group practice Group rehearsals

Maximum Capacity 1 person 2 people

Floor Space 2 3.3 m 2 5.2 m

4 people 6 people 15 people

7.0 m 2 9.0 m 2 35.0 m

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As it could be observed from Table 1, the minimum floor area is 3.3 m for single person 2 practice and 35 m for group rehearsals. According to Mehta et al [1] the reverberation time of a small practice room should be around 0.4 seconds. However, different instruments need different RT values. Some instruments such as flute might provide better listening experience when the RT is high. Bigger volumes of the rooms should increase the RT. Therefore, three 2 2 2 different floor areas are determined such as 8 m , 25 m and 80 m . All these three floor areas are assigned lower and higher ceilings. Table 2 shows the classification of the computer models according to floor area and ceiling heights. According to this distribution of floor area and ceiling heights six different reverberation time values are obtained in the rooms from 0.45 sec. to 2.5 sec. in 500Hz. As it could be observed from the floor plans in Table 2, the rooms have approximately the same shape and the non-parallel walls could easily be observed. There is only one right angle corner in the room. As for the materials, some considerations are made about the low frequency absorption. Normally, common finishing materials such as carpets, curtains and upholstery absorb the high frequencies but not very effective in low frequencies. Therefore, some special materials having low frequency absorption are assigned to the ceiling to increase the performance of some instruments in the room. The RT values given in Table 2 relate to 500 Hz; however, a flat frequency response is obtained except for the high frequency.

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19 INTERNATIONAL CONGRESS ON ACOUSTICS – ICA2007MADRID

Table 2.-The classification of the computer models according to floor area and ceiling height. (The reverberation time and αmean are from 500 Hz) FLOOR AREA

Low ceiling

8 m2

20m3

High ceiling

CEILING HEIGHT

RT=0.45sec. αmean = 0.18

32m3 RT=0.90sec. α mean = 0.09

25 m2

75m3 RT=1.3sec. α mean = 0.07

112m3 RT=1.6sec. α mean = 0.08

80m2

360m3 RT=2.1 sec. α mean = 0.07

480m3 RT=2.5 sec. α mean = 0.12

Auralizations The anechoic recordings of each instrument have been provided by Acoustical Technology in Technical University of Denmark [4]. The anechoic recording of the choir is from Wegner Corporation [5].The duration of the anechoic recordings which were used for the auralization process choir varied between 15 to 30 seconds. Anechoic recordings of all six instruments and the choir have been convolved with the binaural room impulse response (BRIR) of each room, resulting in 42 different auralizations. Each instrument and the choir have auralizations for six different rooms resulting six different sound experiences of each instrument and the choir.

LISTENING TESTS AND QUESTIONNARIES The sound level produced by the instruments is a very important part of this experiment. However, objectively calibrated levels of the recordings were not available. So, in stead the sound power setting for each instrument was made in a close listening position in order to obtain a level as realistic as possible, taking the character of the instrument and the music piece into account. For each instrument the same power setting was kept during the listening tests. Earspeaker Stax SRS-2002 was used during the tests and the driver units for earspeaker were SRM-212. 3 th


In the previous paper the people were asked to rate the rooms according to listening/experiencing of the instrument. However, in this paper, the listening tests were done mainly to investigate the ‘best’ room preference of the professional musicians when they are practicing with their instrument. Each musician listened the auralization of instrument of his expertise in six different rooms (Nine musicians for each instrument and nine conservatory students for the choir). No information about the rooms was given to them prior to the tests. The samples of the rooms were in arbitrary order. The subjects could listen the samples as many times as they wanted before they decide. The same test has been repeated in other day, this time in order to investigate the listening preference of the musicians. This gives the opportunity to compare the musicians ratings with the results of the previous research done with the ordinary people. 63 subjects (between 18 to 40 years old) participated in the listening tests. 38 of them were students in the 9 Eylul University State Conservatory (Izmir, Turkey), 19 of them were instructors in the same university and six of them were members of the Symphony Orchestra. The students participated had an experience of minimum five years. The subjects were not given an audiogram test; however, none of them reported any hearing problems. The listening tests took approximately 45 minutes. RESULTS Figure 1 displays the results of the listening tests. The upper graph from Figure1 shows the preferred best rooms by ordinary people from the previous paper for comparison purpose[3]. The bottom graphs show the ‘best rooms to practice’ and ‘best rooms to listen/experience’ by the professional musicians. The results shown here are grouped according to the floor area.(also refer to Table 2) It is observed that when practicing the preference of the musicians for violin, clarinet and 2 2 trumpet is for the floor area of 8m .The majority chooses the 80m for the choir experience. For 2 2 xylophone and guitar 8m and 25m rooms are chosen. However, the results for the piano vary. (Figure 1) When the musicians are asked for the ‘best rooms to listen’ the results show that 2 majority of them prefer 25m rooms for violin, clarinet, xylophone, guitar, trumpet and choir. The most controversial instrument for the listening experience is the piano as revealed by Figure 1. Figure 2 shows the classification of the instruments and the choir according to the floor area and the ceiling height based on the ‘best rooms to practice’.

The results verify the claims of the musicians that the best room to practice and best room to listen are different for a musician. The listening preferences of the ordinary people and musicians also show important variance. The ordinary people preferred dry rooms (RT is between 0.45-0.90) and reverberant rooms for choir and xylophone (RT is between 2.1-2.5 sec).However, for the musicians all the instruments except for the piano the best choice is the mid-reverberant rooms (1.3-1.6 sec)

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Best rooms by ordinary people 9 8 7 6 5

VIOLIN CLARINET TRUMPET XYLOPHONE PIANO GUITAR CHOIR

4 3 2 1 0 8m2

25m2

Best rooms to practice by musicians

80m2

Best rooms to listen by musicians

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8m2

25m2

80m2

8m2

25m2

80m2

Figure 2.- The ‘best rooms to listen’ for each instrument by ordinary people, the ‘best rooms to practice’ by the musicians, the ‘best rooms to listen’ by the musicians.

Low Ceiling

clarinet piano xylophone

choir violin

High Ceiling

guitar

trumpet

8m2

25m2

80m2

Figure 2.- The classification of the instruments according floor area and ceiling height when practicing. 5 th


CONCLUSIONS The results show that musicians have a clear distinction between the ‘best rooms to practice’ and the ‘best rooms to listen’. In general musicians prefer the dry rooms for the practicing and mid-reverberant rooms for the listening experience. When practicing the dry rooms are preferred violin, clarinet and trumpet.(RT is between 0.45-0,9 2 sec) This reverberation time is achieved best with floor area of 8 m with a low ceiling(2.5m) for violin and clarinet and with a high ceiling(3m) for the trumpet. Xylophone and guitar 2 2 preferences for practicing are divided between 8m and 25m rooms. The reverberant rooms are preferred for the choir. (2.1-2.5 sec) The results for piano vary among all rooms. Based on that information grouping of instruments can be suggested when practice rooms in conservatories are designed The ‘best rooms to listen’ by the musicians shows stronger preference for the mid-reverberant rooms (RT is between 1.3-1.6 sec) violin, clarinet, xylophone, guitar, trumpet and choir. Only controversial instrument is the piano as approximately half of the population prefers the dry and the other half prefers the reverberant rooms. This contradiction is also observed in the results for the practicing. The results of the preceding paper might be considered more in line with the listening tests for the best room to listen. However, considering the design of the practice rooms the results for the best room to practice could be starting point.

References: [1] M. Mehta, J. James, J. Rocafort: Principles and Design. Architectural Acoustics:Principles and Design.

Prentice Hall, Upper Saddle River, New Jersey. (1999) 283-287 [2]Planning Guide for Secondary School Music Facilities. Version 2.2. http://www.eric.ed.gov/ERICDocs/data/, Wenger Corporation, Owatonna, MN. , 2001 [3] K. Saher, J. H. Rindel: How does architecture sound for different musical instrument performances?. Proceedings of Architecture Music Acoustics Conference. Ryerson University. Toronto. Canada. June 810(2006) [4] Music for Archimedes. Anechoic Sound Recordings. Bang&Olufse.CD B&O 101(1992) [5] Anechoic Choral Recordings. Wegner Corporation.Owatonna.MN. (2004)

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