Review of Acoustic Sources Alternatives to a Dodecahedron Speaker

Abstract

An omnidirectional source is required in many acoustic measurements. Commonly a dodecahedron speaker is used but due to various factors (e.g., high cost, transportation difficulties) other acoustic sources are sometimes preferred. In this review, fifteen acoustic source alternatives to a dodecahedron speaker are presented while emphasis is placed on features such as omnidirectionality, repeatability, adequate sound pressure levels, even frequency response, accuracy in measurement of acoustic parameters and fulfillment of ISO 3382-1 source requirements. Some of the alternative acoustic sources have the appropriate features to provide usable results for acoustic measurements, some have acoustic characteristics better than a dodecahedron speaker (e.g., omnidirectionality in the high-frequency range), while some can potentially fulfill the ISO 3382-1 source requirements. Collected data from this review can be used in many areas (e.g., ISO measurements, head-related transfer functions measurements) for the appropriate selection of an acoustic source according to the expected use. Finally, suggestions for uses and future work are given aimed at achieving further advances in this field.

Measurements of Acoustical Parameters in the Ancient Open-Air Theatre of Tyndaris (Sicily, Italy)

“…The effect is shown along the R4-R5-R6 and R7-R8-R9 lines for both S1 and S2 only for the dodecahedral source, and it is not observed along the R1-R2-R3 line. It could be due to the lack of omnidirectionality of the dodecahedral source at the highest frequencies [26,36] that determines selected focusing effects due to the loudspeakers position. Considering firecrackers, it does not exhibit directional characteristics or a very good repeatability [36,48].…”

“…It could be due to the lack of omnidirectionality of the dodecahedral source at the highest frequencies [26,36] that determines selected focusing effects due to the loudspeakers position. Considering firecrackers, it does not exhibit directional characteristics or a very good repeatability [36,48]. Moreover, IR with the dodecahedral source results to be less sharp than those obtained with firecrackers.…”

“…Table 1 shows the distances between the sources and the receivers. Two types of sources were used to measure the IRs as it was considered acoustically and metrologically relevant [36]: firecrackers ("Raudo Manna New Ma1b" and "Perfetto C00015 Raudo New") and a dodecahedral source (Bruel & Kjaer Omnipower sound source 4296). In the former case, the IRs were measured directly by recording the impulse produced by the firecracker blast, while in the latter case, the IRs were obtained after deconvolution of the recorded exponential sine sweep signal, which was 2.73 s long [26].…”

“…The IRs from the dodecahedral source were obtained for both source positions S1 and S2. Firecrackers maximize the signal-to-noise ratio (SNR) which is a considerable advantage in outdoor measurements, but they are also more affected by random effects (e.g., atmospheric conditions) [25,36]. Table 1.…”

Italian-Style Opera Houses: A Historical Review

“…After a successful season of meetings in the 1990s, the community of scholars found standard procedures to qualify the acoustics of historical opera house [119,120], collected in the so-called Ferrara charter. For instance, the Ferrara charter stated the use of dodecadrical sound source [121] instead of alternative sound sources [122] used in some early surveys [73]. Moreover, the charter stated how to place the source on the stage and in the pit [123], and how many receivers must be measured in the stalls and in the boxes [124].…”