Page 35 - Spring2019

covery of the relationship between room volume, materials, and reverberation. Built in 2015, the Philharmonie de Paris is far from rectangular. Its form is most similar to a “vine- yard” style hall, which features a centralized orchestra po- sition surrounded by audience seated in shallow balconies. Led by Jean Nouvel (architect) and Harold Marshall (design acoustician), the design team was selected by competition and was provided with a detailed and prescriptive acoustical brief by the owner’s acoustician (Kahle Acoustics and Altia, 2006). Sabine’s scientifically based acoustical design input for Boston Symphony Hall was limited to its ceiling height. On the other hand, the design of the Philharmonie de Paris was based on decades of research about concert hall acoustics. How do these halls, built under such different circumstances, compare with each other acoustically?
Boston Symphony Hall is known for its generous reverber- ance, warmth, and enveloping sound. Its 2,625 seats are dis- tributed across a shallowly raked floor and two balconies that wrap around the sides of the room, which measures 18,750 m3 in total volume. If the seats were rebuilt today, code re- quirements and current expectations of comfort would sig- nificantly reduce the seat count. The lightly upholstered seats are acoustically important for preserving strength and re- verberance (Beranek, 2016). Heavy, plaster walls reflect low- frequency energy and help to create a warm timbre. The hard and flat lower side walls and undersides of shallow side bal- conies provide strong lateral reflections to the orchestra seat- ing level, and statues along the ornamented upper side walls and deeply coffered ceiling promote diffuse late reflections throughout the room. The large volume above the second balcony fosters the development of late reverberation that is long, relatively loud, and decays smoothly. The perception of clarity in the room varies by listening position and the music being performed. The Boston Symphony Orchestra is also one of the world’s best orchestras, and it knows how to high- light the hall’s acoustical features, particularly for late clas- sical and romantic era repertoire.
is long in time, it is lower in level, which strikes a different balance between reverberance and clarity. In an interview with Kahle (personal communication, 2018), he noted that the high seat count was one of the primary acoustical design challenges and this necessitated the parametrically prescrip- tive design brief. In his words, “an orchestra has a limited sound power, which you have to distribute over more peo- ple...and if you share it, you get less of it.” The seating ar- rangement keeps the audience closer to the musicians, which heightens the sense of intimacy. Lateral reflections are pro- vided by balcony fronts, although the distribution of lateral energy and ensemble balance vary more between seats due to the shape of the room and position of the orchestra. Concave wall surfaces are shaped to scatter sound and avoid focusing. The lengthy but relatively less loud reverberation is gener- ated by an outer volume that is not visible to the audience. The same orchestra playing the same repertoire will sound completely different in Paris compared with Boston, and the quality of the listening experience will depend on where one is sitting, the music being performed, and, most of all, the listener’s expectations and preferences.
Table 2 shows a comparison of parameters measured in both halls. The numbers show some interesting relative differenc- es but do not convey the perceptual significance of these dif- ferences or predict how someone would perceive the acous- tics of either hall from a particular seat. Standard deviation from the average measured parameters should be at least as important as the averages, especially for spatial parameters, although this information is rarely published. None of the measured parameters describe timbre, ensemble balance, or blend. Although the parameters do impart meaning, espe- cially in the context of listening observations and an under- standing of how architectural features in the room impact the acoustics, they do not describe the complete acoustical story or provide a meaningful account of the halls’ dramatic differences.
The Philharmonie de Paris seats 2,400 in a total volume of 30,500 m3, which is over 60% larger than Boston Symphony Hall. One of the results of this significant dif- ference in size is that although the Philharmonie’s reverberation
Table 2. Average mid-frequency parameters measured in Boston Symphony Hall and Philharmonie de Paris
Boston Symphony Hall
Philharmonie de Paris
RTunocc, s 2.5
3.2
RTocc, s 1.9
2.5
EDT, s 2.4
Not reported
Gmid, dB 4.0
2.2
C80, dB JLF −2.6 0.24 −0.7 0.20
Data for Boston Symphony Hall from Beranek (2004) and for Philharmonie de Paris from Scelo et al. (2015).
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