A virtual symphony orchestra created for studying concert hall acoustics
15.11.2011
The doctoral dissertation of Master of Science (Technology) Jukka Pätynen to be publicly examined at Aalto University states that the acoustics of concert halls can be studied in a more versatile manner than before with the help of a virtual symphony orchestra. The new method improves the evaluation of concert hall acoustics and enables performing listening tests in laboratory conditions.
The virtual symphony orchestra refers to an orchestra whose musicians have been replaced by 34 loudspeakers. The loudspeakers are positioned on the concert hall stage in a shape resembling a real symphony orchestra.
Traditionally, studying concert hall acoustics has been based on experts visiting concert halls, listening to musical performances on different nights and comparing the acoustics of different halls based on their experiences. According to Pätynen, however, our acoustic memory is short and the memories of the acoustics of different concert halls fade quickly. Moreover, the performance of an orchestra varies slightly depending on the concert hall and the evening in question.
“With the help of a loudspeaker orchestra, the exact copy of a musical performance can be played in different halls as many times as necessary. When the loudspeaker orchestra is moved from hall to hall, the only variable that changes is the acoustics.”
Anechoic music under the baton of a videoed conductor
The music recorded for the loudspeaker orchestra must be totally anechoic. This is why the virtual symphony orchestra was created in an anechoic room where the musicians recorded their part of the music individually.
“The musicians followed a videoed conductor and listened to a previously recorded pianist from their headphones. Then the parts of all the musicians were synchronised so that the end result was a loudspeaker orchestra playing Mozart or Beethoven.”
By recording the music played by the virtual orchestra in various concert halls, acoustics can also be examined in laboratory conditions. The identically played music is recorded at different listening points by using a microphone that records spatial sound and then used as material for listening tests.
“The test persons of the listening tests can press a button and move from the Finlandia Hall to the Sibelius Hall and compare the acoustics of the two buildings. They can also evaluate the acoustic properties of the halls’ various listening points.”
Pätynen explains that the recordings made in the anechoic room have also been used to study the directivity of orchestra instruments in detail. The dissertation also presents a new method for creating the sound of an orchestra string section from a single recorded instrument. The method is based on tracking the temporal differences of the violinists of a real orchestra. The temporal differences of the virtual musicians are then changed in accordance with these results in addition to making pitch changes.
Jukka Pätynen’s doctoral dissertation "A virtual symphony orchestra for studies on concert hall acoustics" will be presented for public examination and debate in Auditorium T2 at the Aalto University School of Science, Department of Media Technology (Konemiehentie 2, Espoo, Finland), on the 18th of November 2011 at 12 noon.
The dissertation is available online at: http://lib.tkk.fi/Diss/2011/isbn9789526042916/
For further information, please contact: Jukka Pätynen, jukka.patynen [at] aalto [dot] fi, tel. +358 44 058 5547