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Journal of the Acoustical Society of America

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Feb 2005

Volume 117, Issue 2, pp. 465-972

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The effect of a periodic absorptive strip arrangement on an interior sound field in a room

Joo-Bae Park, Karl Grosh, and Yang-Hann Kim

J. Acoust. Soc. Am. Volume 117, Issue 2, pp. 763-770 (2005); (8 pages)

Online Publication Date: 31 Jan 2005

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In this paper we study the effect of periodically arranged sound absorptive strips on the mean acoustic potential energy density distribution of a room. The strips are assumed to be attached on the room’s surface of interest. In order to determine their effect, the mean acoustic potential energy density variation is evaluated as the function of a ratio of the strip’s arrangement period to wavelength. The evaluation demonstrates that the mean acoustic potential energy density tends to converge. In addition, a comparison with a case in which absorptive materials completely cover the selected absorptive plane shows that a periodic arrangement that uses only half of the absorptive material can be more efficient than a total covering, unless the frequency of interest does not coincide with the room’s resonant frequencies. Consequently, the results prove that the ratio of the arrangement period to the wavelength plays an important role in the effectiveness of a periodic absorptive strip arrangement to minimize a room’s mean acoustic potential energy density. © 2005 Acoustical Society of America.
Show PACS
43.55.Dt Sound absorption in enclosures: theory and measurement; use of absorption in offices, commercial and domestic spaces
43.55.Ka Computer simulation of acoustics in enclosures, modeling

A scale value for the balance inside a historical opera house

Nicola Prodi and Sylvia Velecka

J. Acoust. Soc. Am. Volume 117, Issue 2, pp. 771-779 (2005); (9 pages)

Online Publication Date: 31 Jan 2005

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In the framework of opera house acoustics, the term “balance” refers to the acoustical competition between the singer on the stage and the orchestra in the pit. The mechanism allowing the operatic singers to be heard over the orchestra has to do with their skill in enhancing the vocal emission by a peculiar use of the formant frequencies. This vital factor is sensed by the listeners and, apart from the obvious sound power ratio of the stage and the pit sources, is the main cue that helps to formulate a subjective impression of the balance. To achieve its objective qualification, two calibrated sound sources can be placed on the stage and in the pit, respectively, and their sound level difference is measured at the listeners’ seats. The scope of this work is to investigate the relationship between the subjective impression and the objective indicator of the balance and to develop a scale value for the parameter in the case of a historical opera house. For this scope a set of acoustical data from the Teatro Comunale in Ferrara will be used to create synthetic sound fields with controlled conditions of the balance between the stage and the pit. This methodology employs an anechoic piece for soprano (with piano accompaniment) and is implemented in a dead room equipped with an acoustical rendering system. The sound fields are used to investigate the appropriate balance values by means of listening tests. The results of the scaling exercise show that a suitable range of values can be extracted and that the sound from the stage and the pit is perceived as balanced when the loudness difference between the two is comprised within −2.0 dBA and +2.3 dBA. © 2005 Acoustical Society of America.
Show PACS
43.55.Hy Subjective effects in room acoustics, speech in rooms
43.55.Fw Auditorium and enclosure design
43.55.Gx Studies of existing auditoria and enclosures
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